AJP - Heart Information on EB 2010
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
QUICK SEARCH:   [advanced]


     

Am J Physiol Heart Circ Physiol 294: H220-H228, 2008. First published November 2, 2007; doi:10.1152/ajpheart.00968.2007
0363-6135/08 $8.00
This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow All Versions of this Article:
294/1/H220    most recent
00968.2007v1
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in Web of Science
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Xu, M.
Right arrow Articles by Yuan, J. X.-J.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Xu, M.
Right arrow Articles by Yuan, J. X.-J.

Characterization of agonist-induced vasoconstriction in mouse pulmonary artery

Minlin Xu,1 Oleksandr Platoshyn,1 Ayako Makino,1 Wolfgang H. Dillmann,1 Katerina Akassoglou,2 Carmelle V. Remillard,1 and Jason X.-J. Yuan1

Departments of 1Medicine and 2Pharmacology, University of California, San Diego, La Jolla, California

Submitted 21 August 2007 ; accepted in final form 30 October 2007


   ABSTRACT
TOP
 ABSTRACT
METHODS AND MATERIALS
 RESULTS
 DISCUSSION
 GRANTS
 REFERENCES
 
In recent years, transgenic mouse models have been developed to examine the underlying cellular and molecular mechanisms of lung disease and pulmonary vascular disease, such as asthma, pulmonary thromboembolic disease, and pulmonary hypertension. However, there has not been systematic characterization of the basic physiological pulmonary vascular reactivity in normal and transgenic mice. This represents an intellectual "gap", since it is important to characterize basic murine pulmonary vascular reactivity in response to various contractile and relaxant factors to which the pulmonary vasculature is exposed under physiological conditions. The present study evaluates excitation- and pharmacomechanical-contraction coupling in pulmonary arteries (PA) isolated from wild-type BALB/c mice. We demonstrate that both pharmaco- and electromechanical coupling mechanisms exist in mice PA. These arteries are also reactive to stimulation by {alpha}1-adrenergic agonists, serotonin, endothelin-1, vasopressin, and U-46619 (a thromboxane A2 analog). We conclude that the basic vascular responsiveness of mouse PA is similar to those observed in PA of other species, including rat, pig, and human, albeit on a different scale and to varying amplitudes.

pharmacology; store depletion; excitation-contraction coupling; G protein-coupled receptors

MICE, ESPECIALLY TRANSGENIC or knockout variants, are increasingly being used to study disease mechanisms. With respect to pulmonary hypertension, transgenic or knockout mouse models have been developed to evaluate the modulation of pulmonary vasoconstriction and remodeling due to 1) endothelial nitric oxide synthase disruption (18, 47, 57); 2) vasoactive and mitogenic agonists, such as hypoxia-inducible factors-1{alpha} (63) and -2{alpha} (2), calcitonin gene-related peptide (5), serotonin (5-HT) (9, 32, 34, 45), matrix metalloproteinases (67), transforming growth factor-β (35), and vasoactive intestinal peptide (51); 3) bone morphogenetic protein receptor type II gene mutations and altered bone morphogenetic protein signaling (19, 28, 40, 62); 4) altered function of ion channels (12) and transporters (49); and 5) altered superoxide production (36, 38). Despite these studies, there is still relatively little information regarding the basic characterization of the pulmonary vascular reactivity in normal mice. Nor have the excitation-contraction coupling mechanisms, pharmacological properties of vasoactive response to agonists, been evaluated completely in wild-type mice. This represents an intellectual gap, since it is important to characterize basic murine pulmonary vascular reactivity in response to various contractile and relaxant factors to which the pulmonary vasculature is exposed under physiological conditions. The aim of this study was to characterize pulmonary arterial (PA) excitation-contraction coupling and pharmacological properties of PA using isolated PA rings from mice.


   METHODS AND MATERIALS
TOP
 ABSTRACT
 METHODS AND MATERIALS
RESULTS
 DISCUSSION
 GRANTS
 REFERENCES
 
Isolation of PA rings. Male 5- to 8-wk-old BALB/c mice were used in this study. Use of mice for the experiments presented in this study was approved by the Institutional Animal Care and Use Committee (IACUC) of the University of California, San Diego. After decapitation using a procedure approved by the IACUC, the lungs were quickly removed from the mouse, washed with cold saline (to removed blood from the lung tissue), and placed in a dissection plate. Under a stereomicroscope, the right and left branches of the intrapulmonary arteries (third and fourth divisions) were isolated from the mice within 45 min from the time when the lungs were removed from the decapitated mice. Adipose and connective tissues were carefully removed with fine forceps and ophthalmological scissors, and the remaining arteries were cut into 1.5-mm-long rings. The arterial rings in which the vascular wall was damaged or contained small branches were discarded; only rings with an intact wall were used for our experiments.

Tension measurement. Two tungsten hooks (75-µm diameter) were inserted through the lumen of the PA rings. One hook was mounted on the bottom of a perfusion chamber, and the other was connected to an isometric force transducer (Harvard Apparatus). Isometric tension was continuously monitored and acquired using DATAQ software (DATAQ Instruments). Unless indicated otherwise, resting passive tension was set at 300 mg, and the rings were equilibrated for 1 h at resting tension and then challenged three times with 40 mM K+ (40K) perfusate to obtain a stable contractile response.

Isolated PA rings were superfused with modified Krebs solution (MKS; at 37°C) consisting of the following (in mM): 138 NaCl, 1.8 CaCl2, 4.7 KCl, 1.2 MgSO4, 1.2 NaH2PO4, 5 HEPES, and 10 glucose (pH 7.4). For Ca2+-free solution, CaCl2 was replaced by equimolar MgCl2, and 1 mM EGTA was added to chelate residual Ca2+. In the high-K+ solution, NaCl was replaced by equimolar KCl to maintain osmolarity. The active tension induced by agonists was normalized by the basal tension and expressed as net increase in tension (mg).

Chemicals and reagents. 4-Aminopyridine (4-AP), sodium nitroprusside (SNP; Fluka), 5-HT, acetylcholine (ACh), and bradykinin (BK) were dissolved directly into MKS on the day of use. Nifedipine (Nif) and cyclopiazonic acid were prepared as 1 and 30 mM stocks, respectively, in dimethyl sulfoxide. U-46619 was prepared as a stock in ethanol. Phenylephrine (PE), endothelin-1 (ET-1), and vasopressin (VP) were prepared as concentrated stock solutions in distilled water. All stock solutions were aliquoted and kept frozen at –20°C until use. On the day of experiments, aliquots of the stock solutions were dissolved in MKS to the proper concentrations. The pH values of all solutions were measured after addition of the drugs and readjusted to 7.4. All drugs were from Sigma Chemical, unless otherwise indicated.

Histological preparation. After contraction experiments, the PA rings were fixed overnight in 10% neutral buffered formalin. The formalin-fixed rings were serially cut for microscopic examination. The vessel tissues were processed and embedded in paraffin blocks in an automatic tissue processor (Sakura Tissue-Tek VIP; Sakura Finetek). The paraffin-embedded tissues were cut in 5-µm-thick sections for staining with either lectin (endothelium specific) or {alpha}-actin (smooth muscle specific).

Statistics. The composite data are expressed as means ± SE. Statistical analysis was performed using paired or unpaired Student's t-test or ANOVA and post hoc tests (Student-Newman-Keuls) where appropriate. Differences were considered to be significant at P < 0.05.


   RESULTS
TOP
 ABSTRACT
 METHODS AND MATERIALS
 RESULTS
DISCUSSION
 GRANTS
 REFERENCES
 
Morphological feature of PA isolated for contraction experiments. The PA rings used in this study were isolated from third- to fourth-order intrapulmonary arterial branches (Fig. 1A). Internal diameter of the arteries ranged from 200 to 500 µm. Bright-field and fluorescent images (Fig. 1B) show that the vessel wall was intact, with a distinct intraluminal wall composed of an endothelial cell monolayer, which can be stained with lectin and multiple layers of smooth muscle cells identified by {alpha}-actin staining (Fig. 1B, right). These structural characteristics are similar to those our laboratory previously identified in rat PA rings (31).


Figure 1
View larger version (92K):
[in this window]
[in a new window]

  		Fig. 1. Images of mouse pulmonary artery (PA). A: phase contrast image of intrapulmonary arterial branches isolated from the left lung at x1.0 (left) and the zoomed image showing the branch that is used for the experiment (right). B: bright-field image of mouse PA section highlighting the vascular wall and the intraluminal space (left). In the image on the right, the artery was stained with lectin and smooth muscle {alpha}-actin (SMA) to identify PA endothelial cells (PAEC, green) along the luminal side of the artery, and the PA smooth muscle cells (PASMC, red) composing the majority of the vascular wall.

 
Zero-stress state of left and right branches of PA. If a blood vessel is cut open or all loads are removed, the circular shape opens up, and the wall becomes a sector; this is the blood vessel in its zero-stress state (20, 59). This illustrates that, compared with the in vivo or no-load (i.e., no transmural pressure or longitudinal stress) states, there are residual stresses and strains in blood vessels.

Figure 2A depicts images of left and right PA in their native state, as well as after being cut longitudinally to relieve stresses. The zero-stress state after cutting was calculated as the angle ({theta}) of opening of the resting artery. Despite evidence that the opening angles at the zero-stress states vary in third- to ninth-order human PA (27), we found that the opening angles at the zero-stress states were comparable between left and right branches of intrapulmonary arteries (94.2 ± 9.10 vs. 88.2 ± 7.6°; P = 0.6218).


Figure 2
View larger version (56K):
[in this window]
[in a new window]

  		Fig. 2. Comparative residual angle or zero-stress state in PA rings isolated from left and right lungs. A: at no-load state (top), the internal pressure, external pressure, and longitudinal stress in a short-ring-shaped segment of the left and right PA. When the rings are cut longitudinally, the zero-stress state (represented as the residual angle {theta} subtended between two lines originating from midpoint tips of the inner wall) is increased. B: summarized {theta} values (n = 6) obtained for third branches of left and right PA. The residual angles are not statistically different between the left and right PA groups.

 
Optimal basal tension for high K+ and agonist-mediated PA contraction. An optimal basal tension is required for blood vessels to obtain maximal active contraction. In isolated mouse PA rings, increasing the basal tension from 100 to 300 mg significantly augmented the 40K-induced active tension (Fig. 3). Increasing the basal tension from 300 to 600 mg did not significantly change the active tension, whereas basal tension beyond 600 mg actually reduced the 40K-mediated active tension (Fig. 3B). These data suggest an optimal 300-mg basal tension for the mouse intrapulmonary arteries with diameters of 200–500 µm. Therefore, we used 300-mg basal tension for all of the following experiments.


Figure 3
View larger version (22K):
[in this window]
[in a new window]

  		Fig. 3. Establishment of optimal basal tension for mouse PA rings. A: rings were equilibrated at incremental basal tensions ranging between 100 and 800 mg for 30–60 min before being challenged with 40 mM K+ (40K) solution to induce contraction or active tension. B: summarized 40K tension from mouse PA rings equilibrated at different basal tension. Results are means ± SE obtained from 4 experiments. Solid line represents the best fit of 40K-induced tension, with a plateau appearing at ~300 mg basal tension.

 
Dose-response curves of high K+- and PE-induced pulmonary vasoconstriction. Two basic excitation-coupling mechanisms control pulmonary vascular tone: 1) electromechanical coupling, the mechanism that causes contraction or relaxation through changes in membrane potential; and 2) pharmacomechanical coupling, the complex of mechanisms that can cause contraction or relaxation by mechanisms not mediated by changes in membrane potential (56). We verified that pathways leading to both contractile mechanisms were intact in isolated PA rings and that they contribute to the regulation of vascular tone in mouse PA rings.

Raising extracellular K+ concentration ([K+]o) (e.g., from 4.7 to 40 mM) shifts the K+ equilibrium potential and causes membrane depolarization. Subsequent opening of voltage-dependent Ca2+ channels promotes Ca2+ influx, increases cytosolic Ca2+ concentration, and causes vasoconstriction. In PA rings with a 300-mg basal tension, increasing [K+]o from 4.7 (in MKS) to 10, 20, 40, 60, 80, and 120 mM significantly increased the amplitude of active tension. The dose-response curve was almost linear at [K+]o between 20 and 40 mM and gradually stabilized (or approached to the plateau phase) when [K+]o reached 60–80 mM. The EC50 for high-K+-mediated active tension in mouse PA rings is ~35 mM (Fig. 4A).


Figure 4
View larger version (16K):
[in this window]
[in a new window]

  		Fig. 4. Generation of active tension by electro- or pharmacomechanical stimuli. Rings were stimulated with 10–120 mM K+ (A) or 0.2–200 nM phenylephrine (PE; B). For each protocol, representative tracings are depicted in a, absolute active tension (mean ± SE) is depicted in b, and active tension (mean ± SE) normalized to the maximum tension generated by 100 mM K+ (A) or 100 nM PE (B) is shown in c. Summarized data are from 3 and 4 rings for K+ and PE experiments, respectively. [K+] and [PE], K+ and PE concentration, respectively.

 
The {alpha}-adrenergic receptor agonist, PE, also caused vasoconstriction in mouse PA rings. The minimal dose of PE to induce PA contraction was 2 nM. The steepest increase of active tension occurred at doses between 5 and 20 nM; the EC50 for PE-induced pulmonary vasoconstriction was ~10 nM (Fig. 4B). The data obtained from these experiments indicate that electromechanical and pharmacomechanical coupling mechanisms are both involved in the regulation of mouse pulmonary vascular tone.

Ca2+ dependence of high-K+- and agonist-mediated PA contraction. Extracellular Ca2+ influx is required for both electro- and pharmacomechanical coupling to occur. Removal of extracellular Ca2+ almost abolished 25 mM K+-mediated PA contraction, whereas extracellular application of the voltage-dependent Ca2+ channel blocker Nif (100 nM) also significantly inhibited 25 mM K+-induced active tension. As shown in Fig. 5, the 25 mM K+-induced active tension was 257.7 ± 4.2 mg in PA rings superfused with 1.8 mM Ca2+-containing MKS, 14.5 ± 6.8 mg (a 94% inhibition; P < 0.001) in PA rings superfused with Ca2+-free MKS, and 286.0 ± 44.2 mg when extracellular Ca2+ was restored (Fig. 5A). Furthermore, the 25 mM K+-induced active tensions were 325.0 ± 29.3, 22.0 ± 14.4 (a 93% inhibition), and 269.0 ± 35.5 mg before, during, and after application of Nif (Fig. 5B). These data indicate that 25 mM K+-induced PA contraction is mainly due to membrane depolarization-mediated Ca2+ influx through Nif-sensitive, voltage-dependent Ca2+ channels in PA smooth muscle cells (PASMCs).


Figure 5
View larger version (21K):
[in this window]
[in a new window]

  		Fig. 5. Modulation of Ca2+ influx during electro- or pharmacomechanical contraction. Mouse PA were treated with 25 mM K+ (25K; A and B) or 200 nM PE (C and D). After peak contraction was attained, arteries were exposed to either Ca2+-free (0Ca) or 100 nM nifedipine (Nif)-containing solution to attenuate Ca2+ influx. Representative traces and summarized data (mean ± SE) are presented for each experimental condition. Summarized data show active tension induced by 25K (A and B; bottom) or PE (C and D; bottom) before (Cont), during (0Ca or Nif), and after (Wash) exposure to 0Ca or Nif-containing solution. ***P < 0.001 vs. control.

 
In PA rings precontracted with PE (200 nM), removal of extracellular Ca2+ reversibly reduced the active tension from 484.0 ± 49.8 to 31.0 ± 24.5 mg (a 94% inhibition; P < 0.001) (Fig. 5C). In contrast to our observation with 25 mM K+, extracellular application of Nif (100 nM) reduced the PE-induced active tension only by 29% (from 523.5 ± 47.7 to 369.4 ± 54.1 mg; P < 0.001) (Fig. 5D). From these data, we conclude that PE-induced PA contraction not only involves Ca2+ influx through Nif-sensitive, voltage-dependent Ca2+ channels (e.g., L- and T-type channels), but also involves Ca2+ mobilization from intracellular stores (e.g., sarcoplasmic or endoplasmic reticulum) and Ca2+ influx through Nif-insensitive Ca2+ channels.

Activation of various receptors causes comparable PA contraction. In addition to high K+ and PE, extracellular application of 5-HT (5 µM), ET-1 (0.1 µM), VP (10 µM), U-46619 (10 µM, a thromboxane A2 analog), and thrombin (10 U/ml) also reversibly constricted murine PA rings (Fig. 6, A–E). The level of maximal active tension and the kinetics of tension rise both vary dramatically among different agonists (Fig. 6, F and G). For example, 5-HT- and U-46619-mediated contraction are composed of a rapid initial increase in tension followed by a slow tension increase up to a plateau; in comparison, the thrombin-mediated initial increase in tension seems to be much slower than 5-HT- and U-46619-mediated tension increase (Fig. 6G). The amplitude of active tension induced by ET-1 and VP was much smaller than that induced by other agonists tested, but the kinetics of tension rise (determined by the time required for tension to reach the maximal level) was much faster than thrombin-mediated contraction (Fig. 6G, left). Furthermore, 5-HT- and U-46619-mediated PA contraction seemed to be comparable in terms of the level of maximal active tension and the kinetics of tension development (Fig. 6G, right). Moreover, 5-HT- and U-46619-mediated active tension was also similar to thrombin-mediated PA contraction, but the rise in tension in 5-HT- and U-46619-mediated contraction was much faster than that induced by thrombin (Fig. 6G).


Figure 6
View larger version (14K):
[in this window]
[in a new window]

  		Fig. 6. Effect of different vasoactive agonists on mouse PA tension. Representative tension records (left) and summarized data (right) are presented for rings stimulated with 5 µM serotonin (5-HT; n = 13; A), 0.1 µM endothelin-1 (ET-1; n = 9; B), 10 µM vasopressin (VP; n = 6; C), 10 µM U-46619 (n = 8; D), and 10 U/ml thrombin (n = 8; E). F: comparisons of active tension (mean ± SE) generated by each agonist. ***P < 0.001 vs. control. G: time course of normalized active tension in PA rings induced by ET-1, VP, and thrombin (Throm) (left), as well as by 5-HT and U-46619 (U4) (right).

 
Inhibition of membrane K+ channels induces membrane depolarization and causes PA contraction. Membrane depolarization can be caused either by raising [K+]o or by blockade of K+ channels that are active under the resting conditions. In human and rat PASMC, inhibition of K+ channels, especially voltage-gated K+ channels, with 4-AP causes membrane depolarization, opens voltage-dependent Ca2+ channels, and increases cytosolic Ca2+ concentration (64, 65). As shown in Fig. 7, treatment of isolated mouse PA rings with 10 mM 4-AP significantly increased active tension. Removal of extracellular Ca2+ markedly abolished 4-AP-induced PA contraction, indicating the contraction was mainly induced by Ca2+ influx through voltage-dependent Ca2+ channels (data not shown). The 4-AP-induced active tension in mouse PA was associated with oscillatory contraction (Fig. 7B), which has never been demonstrated in rat PA rings. The oscillation is mainly due to a balance between Ca2+ influx and extrusion and/or Ca2+ release and sequestration. The 4-AP-induced oscillatory contraction thus suggests that inhibition of voltage-gated K+ channels and membrane depolarization may also indirectly activate mechanisms or pathways for Ca2+ extrusion (e.g., via the forward mode of Na+/Ca2+ exchange) and sequestration (e.g., via sarcoplasmic/endoplasmic reticulum Ca2+-Mg2+-ATPase) in mouse PASMCs.


Figure 7
View larger version (17K):
[in this window]
[in a new window]

  		Fig. 7. Inhibition of voltage-gated K+ channels causes mouse PA contraction. A: representative tension trace from a mouse PA ring treated with 10 mM 4-aminopyridine (4-AP) for 20 min. B: contraction by 4-AP was characterized by oscillations, which increased with frequency from the onset of 4-AP (subpanel a enlarged from A) to the end of the 20 min exposure (subpanel b enlarged from A). C: summarized data (means ± SE) from 9 mouse PA rings before (Cont), during (4-AP), and after (Wash) treatment with 4-AP. ***P < 0.001 vs. control.

 
Inability of ACh to cause vasodilation in isolated mouse PA rings. In human and rat PA rings, ACh is a potent endothelium-dependent vasodilator that activates endothelial muscarinic receptors, triggers nitric oxide (NO) synthase, and increases NO production and release. In isolated mouse PA rings with intact endothelium, however, ACh (10 µM) further increased active tension in mouse PA rings precontracted with high K+ (25 and 40 mM K+) (Fig. 8, A and B) or 20 nM PE (Fig. 8C).


Figure 8
View larger version (17K):
[in this window]
[in a new window]

  		Fig. 8. Acetylcholine (ACh) differentially alters 25K- and PE-induced active tension in endothelium-intact mouse PA. A: representative tension record (top) showing 25K-induced active tension in the presence or absence of ACh (10 µM). Summarized data (mean ± SE) show absolute tension before (basal) and after application of 25K in the absence (25K) and presence (25K+ACh) of ACh (bottom left; n = 7), and 25K-induced active tension with (ACh) or without (Cont) ACh treatment (bottom right; n = 7). B: summarized data (mean ± SE) showing absolute tension before (basal) and after application of 40K in the absence (40K) and presence (40K+ACh) of ACh (left; n = 8), and 40K-induced active tension with (ACh) or without (Cont) ACh treatment (right; n = 8). C: representative tension record (left) showing 20 nM PE-induced active tensions in the presence or absence of ACh (10 µM). Summarized data (mean ± SE) show absolute tension before (basal) and after application of PE in the absence (PE-cont) and presence (PE-ACh) of ACh (right; n = 4). ***P < 0.001, *P < 0.05 vs. basal or control.

 
Histological data showed that the endothelial cells were present in the arterial rings used for the experiments (Fig. 9A). Extracellular application of BK (20 µM), an endothelium-dependent vasodilator, significantly reduced active tension in PA rings preconstricted with 40K (Fig. 9, B and C), indicating that the endothelium is functionally normal in the isolated PA rings used in this study.


Figure 9
View larger version (31K):
[in this window]
[in a new window]

  		Fig. 9. Bradykinin (BK) causes vasodilation in endothelium-intact mouse PA. A: fluorescence image of a PA segment used for the contraction experiments. PA smooth muscle was stained in red with smooth muscle {alpha}-actin, while PA endothelium stained in green with lectin. B: representative tension record showing 40K-induced active tension before and during application of BK (20 µM). C: summarized data (mean ± SE) showing absolute tension before (basal) and after application of 40K in the absence (Cont) and presence (BK) of BK (left; n = 4), and 40K-induced active tension with (BK) or without (Cont) BK treatment (right; n = 4). **P < 0.01 vs. basal or 40K-BK.

 
Although ACh was unable to cause pulmonary vasodilation in rings with an intact endothelium, extracellular application of the NO donor SNP (100 nM) significantly reduced (67.4 ± 7.8% reduction) 25 mM K+- and PE (200 nM)-induced PA contraction (Fig. 10). The IC50 for SNP-mediated PA relaxation is ~5 nM (Fig. 10B), indicating that mouse PA smooth muscle is indeed sensitive to NO. The inability of ACh to cause vasodilation in endothelium-intact PA rings suggests that 1) ACh-induced muscarinic receptor activation is not enough to activate endothelial NO synthase (eNOS) in mouse PA endothelium; 2) the expression level and basal activity of eNOS are very low in mouse PA endothelium; 3) NO production in mouse PA endothelium can be rapidly deactivated or scavenged by potentially high levels of reactive oxygen species in endothelial and smooth muscle cells; and 4) the level of muscarinic receptors in mouse PASMCs is much higher than in PA endothelial cells.


Figure 10
View larger version (20K):
[in this window]
[in a new window]

  		Fig. 10. Effect of nitric oxide on high K+- or PE-induced PA contraction. A: representative tension trace (left) and summarized data (right; n = 4) from arteries precontracted with 25K before treatment with the nitric oxide donor sodium nitroprusside (SNP; 100 nM) for 15 min. B: dose-tension response to incremental doses of SNP from 0 (Cont) to 1 µM. IC50 was determined from a Boltzmann fit to the data points. C: representative tension trace (left) and summarized tension (right; n = 4) from arteries precontracted with 200 nM PE before treatment with SNP. ***P < 0.001 vs. control.

 

   DISCUSSION
TOP
 ABSTRACT
 METHODS AND MATERIALS
 RESULTS
 DISCUSSION
GRANTS
 REFERENCES
 
Potential role of pulmonary vascular reactivity in pathogenic and therapeutic mechanisms involved in pulmonary vascular disease using the mouse vasculature is a relatively novel field of study, most notably due to the development of transgenic animals. A significant number of studies have evaluated the vasoreactivity of aorta to K+ (39, 58), angiotensin II (58, 71), U-44619 (48, 58), sphingosine 1-phosphate (41), ATP (23), UTP (23), ACh (6, 39, 72), nitric oxide (26), and PE (39). In contrast, only a few studies have examined the mechanical properties of mouse PA in response to vasoactive stimuli, such as K+ (30), Nif (30), levcromakalim (30), 5-HT (37), ACh (57), and noradrenaline (70). In many cases, vasoreactivity was tested in transgenic animals, but not in their wild-type littermates. Our data present comprehensive information regarding basal electro- and pharmacomechanical coupling in isolated mouse PA rings.

The optimal basal tension in our preparations (200–500 µm in diameter) was ~300 mg. This value is within the 200–1,000 mg optimal tension range used in other mouse PA studies (30, 37, 57, 70); the wide range is likely due to variability in the size of the arteries and strain of mice used. That said, the crux of our study rests on the vasoreactivity of mouse PA rings to different stimuli. Our findings suggest that the mouse PA bears similar electropharmacological mechanical properties to PA rings from rats (7, 13, 22, 42, 44, 46, 54, 60, 61, 68) and humans (24, 55). For example, membrane depolarization by high K+ caused a slow and sustained contraction in mouse PA rings; the kinetics are very similar to that observed in rat PA (1, 54, 66, 68) and human (55) PA rings. Removal of extracellular Ca2+ and application of Nif almost abolished the high K+-mediated PA contraction, as in rat (66). However, while PE induced contraction similarly in mouse and rat PA (44, 52), removal of extracellular Ca2+ almost abolished the PE-induced contraction, but Nif treatment only reduced the active tension by 60%, indicating that Ca2+ resources other than influx via voltage-dependent Ca2+ channels are involved in agonist-mediated PA contraction.

Murine PA responses to other agonists were also similar to that observed in isolated PA rings from other species. For example, SNP produced endothelium-independent vasodilation of mouse PA rings precontracted with either 25 mM K+ or 200 nM PE, similar to what has been reported previously for rat PA (54, 66, 68). However, ACh failed to induce vasodilation in mouse PA rings with intact endothelium (while BK significantly inhibited the active tension in the PA rings), which is quite different from the results obtained from PA rings isolated from humans, rats, and dogs. This may suggest that the NO signaling system is intact in mouse PA, but that the activation of muscarinic receptors in endothelium by ACh is not sufficient (or masked by the contractile effect of ACh-mediated activation of muscarinic receptors in PASMCs) to activate this signaling cascade. In addition to ACh-mediated eNOS activation and NO production in endothelium, ACh-mediated production of endothelium-derived hyperpolarizing factors (EDHF) also contributes to ACh-induced vasodilation in many vessel types isolated from humans, rats, and dogs (3). However, it is unclear whether ACh-induced production or release of EDHF (e.g., K+ and epoxyeicosatrienoic acids) (3, 4, 14) in endothelial cells and/or EDHF-induced activation of K+ channels in smooth muscle cells is different between PA from mice and other species (e.g., rats, dogs, and humans).

The contractile response we observed in mouse PA rings to vasoactive substances like ET-1, 5-HT, and the thromboxane A2 analog U-44619 were characteristically similar to that observed in PA from other species (8, 10, 11, 24, 25, 33, 37, 42, 43, 52, 55, 60, 69). The contractile response to thrombin observed in mouse PA rings was also similar to that observed by others in porcine PA rings (21). However, canine PA do not respond to thrombin with a change in tension (29), while human PA dilate following exposure to thrombin (24). The thrombin response relies on the presence of endothelium and nature of G protein-coupled protease-activated receptors on the plasma membrane. Therefore, it is possible that the protease-activated receptors in mouse and canine PA differ from those in human and canine PA in terms of function, expression, and distribution (e.g., in PA smooth muscle and endothelial cells).

The response to VP represented the only deviation. In isolated mouse PA, we observed a slight, yet significant increase in tension (Fig. 6), which was completely reversible upon washout of VP. In contrast, VP has been reported to cause endothelium-dependent relaxation of PA isolated from rats (15, 16), humans (53), and dogs (17, 50), presumably due to VP inducing the release of endothelium-derived NO. In our experiments with mouse PA, the endothelium was intact; therefore, precisely why the tensile response to VP was opposite between PA isolated from mice and other species (e.g., rat, humans, and dogs) is unclear.

From our study, we can conclude that the physiological responses of mouse PA are highly similar to those previously reported in PA preparations from other species. The only exceptions are 1) the contractile response to VP and thrombin, and 2) the inability of ACh to cause vasodilation in endothelium-intact arteries. While no explanation is currently available to explain these latter differential responses, we have shown that the mouse represents an excellent study model for the evaluation of pulmonary vascular functions, such as excitation-contraction coupling, vasoreactivity, and drug response.


   GRANTS
TOP
 ABSTRACT
 METHODS AND MATERIALS
 RESULTS
 DISCUSSION
 GRANTS
REFERENCES
 
This work was supported in part by grants from the National Heart, Lung, and Blood Institute (HL064945, HL054043, and HL066012).


   ACKNOWLEDGMENTS
 
We thank A. Nicholson for technical assistance.


   FOOTNOTES
 

Address for reprint requests and other correspondence: J. X.-J. Yuan, Division of Pulmonary and Critical Care Medicine, Dept. of Medicine, Univ. of California, San Diego, 9500 Gilman Dr., MC 0725, La Jolla, CA 92093–0725 (e-mail: xiyuan{at}ucsd.edu)

The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.


   REFERENCES
TOP
 ABSTRACT
 METHODS AND MATERIALS
 RESULTS
 DISCUSSION
 GRANTS
 REFERENCES
 

  1. Bennie RE, Packer CS, Powell DR, Jin N, Rhoades RA. Biphasic contractile response of pulmonary artery to hypoxia. Am J Physiol Lung Cell Mol Physiol 261: L156–L163, 1991.[Abstract/Free Full Text]
  2. Brusselmans K, Compernolle V, Tjwa M, Wiesener MS, Maxwell PH, Collen D, Carmeliet P. Heterozygous deficiency of hypoxia-inducible factor-2{alpha} protects mice against pulmonary hypertension and right ventricular dysfunction during prolonged hypoxia. J Clin Invest 111: 1519–1527, 2003.[CrossRef][Web of Science][Medline]
  3. Busse R, Edwards G, Félétou M, Fleming I, Vanhoutte PM, Weston AH. EDHF: bringing the concepts together. Trends Pharmacol Sci 23: 374–380, 2002.[CrossRef][Medline]
  4. Campbell WB, Gebremedhin D, Pratt PF, Harder DR. Identification of epoxyeicosatrienoic acids as endothelium-derived hyperpolarizing factors. Circ Res 78: 415–423, 1996.[Abstract/Free Full Text]
  5. Champion HC, Bivalacqua TJ, Toyoda K, Heistad DD, Hyman AL, Kadowitz PJ. In vivo gene transfer of prepro-calcitonin gene-related peptide to the lung attenuates chronic hypoxia-induced pulmonary hypertension in the mouse. Circulation 101: 923–930, 2000.[Abstract/Free Full Text]
  6. Chataigneau T, Félétou M, Huang PL, Fishman MC, Duhault J, Vanhoutte PM. Acetylcholine-induced relaxation in blood vessels from endothelial nitric oxide synthase knockout mice. Br J Pharmacol 126: 219–226, 1999.[CrossRef][Web of Science][Medline]
  7. Chen G, Suzuki H, Weston AH. Acetylcholine releases endothelium-derived hyperpolarizing factor and EDRF from rat blood vessels. Br J Pharmacol 95: 1165–1174, 1988.[Web of Science][Medline]
  8. Chen YF, Oparil S. Endothelin and pulmonary hypertension. J Cardiovasc Pharmacol 35: S49–S53, 2000.[Web of Science][Medline]
  9. Chruscinski A, Brede ME, Meinel L, Lohse MJ, Kobilka BK, Hein L. Differential distribution of β-adrenergic receptor subtypes in blood vessels of knockout mice lacking β1- or β2-adrenergic receptors. Mol Pharmacol 60: 955–962, 2001.[Abstract/Free Full Text]
  10. Cogolludo A, Moreno L, Bosca L, Tamargo J, Perez-Vizcaino F. Thromboxane A2-induced inhibition of voltage-gated K+ channels and pulmonary vasoconstriction. Role of protein kinase C{zeta}. Circ Res 93: 656–663, 2003.[Abstract/Free Full Text]
  11. Demiryurek AT, Wadsworth RM, Kane KA. Effects of hypoxia on isolated intrapulmonary arteries from the sheep. Pulm Pharmacol 4: 158–164, 1991.[CrossRef][Web of Science][Medline]
  12. Dietrich A, Mederos y Schnitzler M, Gollasch M, Gross V, Storch U, Dubrovska G, Lauterbach B, Herz U, Obst M, Essin K, Renz H, Luft FC, Gudermann T, and Birnbaumer L. Increased vascular smooth muscle contractility in TRPC6–/– mice. Mol Cell Biol 25: 6980–6989, 2005.[Abstract/Free Full Text]
  13. Doggrell SA, Wanstall JC, Gambino A. Functional effects of 4-aminopyridine (4-AP) on pulmonary and systemic vessels from normoxic control and hypoxic pulmonary hypertensive rats. Naunyn Schmiedebergs Arch Pharmacol 360: 317–323, 1999.[CrossRef][Web of Science][Medline]
  14. Edwards G, Dora KA, Gardener MJ, Garland CJ, Weston AH. K+ is an endothelium-derived hyperpolarizing factor in rat arteries. Nature 396: 269–272, 1998.[CrossRef][Medline]
  15. Eichinger MR, Walker BR. Enhanced pulmonary arterial dilation to arginine vasopressin in chronically hypoxic rats. Am J Physiol Heart Circ Physiol 267: H2413–H2419, 1994.[Abstract/Free Full Text]
  16. Eichinger MR, Walker BR. Segmental heterogeneity of NO-mediated pulmonary vasodilation in rats. Am J Physiol Heart Circ Physiol 267: H494–H499, 1994.[Abstract/Free Full Text]
  17. Evora PR, Pearson PJ, Schaff HV. Arginine vasopressin induces endothelium-dependent vasodilatation of the pulmonary artery. V1-receptor-mediated production of nitric oxide. Chest 103: 1241–1245, 1993.[CrossRef][Web of Science][Medline]
  18. Fagan KA, Tyler RC, Sato K, Fouty BW, Morris KG Jr, Huang PL, McMurtry IF, Rodman DM. Relative contributions of endothelial, inducible, and neuronal NOS to tone in the murine pulmonary circulation. Am J Physiol Lung Cell Mol Physiol 277: L472–L478, 1999.[Abstract/Free Full Text]
  19. Frank DB, Abtahi A, Yamaguchi DJ, Manning S, Shyr Y, Pozzi A, Baldwin HS, Johnson JE, de Caestecker MP. Bone morphogenetic protein 4 promotes pulmonary vascular remodeling in hypoxic pulmonary hypertension. Circ Res 97: 496–504, 2005.[Abstract/Free Full Text]
  20. Fung YC. What principle governs the stress distribution in living organisms. In: Biomechanics in China, Japan, and U.S.A., edited by Fung YC. Beijing, China: Science Press, 1983, p. 1–13.
  21. Glusa E, Bretschneider E, Paintz M. Contractile effects of thrombin in porcine pulmonary arteries and the influence of thrombin inhibitors. Naunyn Schmiedebergs Arch Pharmacol 349: 101–106, 1994.[Web of Science][Medline]
  22. Gonzalez de la Fuente P, Savineau JP, Marthan R. Control of pulmonary vascular smooth muscle tone by sarcoplasmic reticulum Ca2+ pump blockers: thapsigargin and cyclopiazonic acid. Pflügers Arch 429: 617–624, 1995.[CrossRef][Web of Science][Medline]
  23. Guns PJDF, Van Assche T, Fransen P, Robaye B, Boeynaems JM, Bult H. Endothelium-dependent relaxation evoked by ATP and UTP in the aorta of P2Y2-deficient mice. Br J Pharmacol 147: 569–574, 2006.[CrossRef][Web of Science][Medline]
  24. Hamilton JR, Moffatt JD, Frauman AG, Cocks TM. Protease-activated receptor (PAR) 1 but not PAR2 or PAR4 mediates endothelium-dependent relaxation to thrombin and trypsin in human pulmonary arteries. J Cardiovasc Pharmacol 38: 108–119, 2001.[CrossRef][Web of Science][Medline]
  25. Horgan MJ, Pinheiro JMB, Malik AB. Mechanism of endothelin-1-induced pulmonary vasoconstriction. Circ Res 69: 157–164, 1991.[Abstract/Free Full Text]
  26. Horváth B, Orsy P, Benyó Z. Endothelial NOS-mediated relaxations of isolated thoracic aorta of the C57BL/6J mouse: a methodological study. J Cardiovasc Pharmacol 45: 225–231, 2005.[CrossRef][Web of Science][Medline]
  27. Huang W, Yen RT. Zero-stress states of human pulmonary arteries and veins. J Appl Physiol 85: 867–873, 1998.[Abstract/Free Full Text]
  28. Izumi N, Mizuguchi S, Inagaki Y, Saika S, Kawada N, Nakajima Y, Inoue K, Suehiro S, Friedman SL, Ikeda K. BMP-7 opposes TGF-β1-mediated collagen induction in mouse pulmonary myofibroblasts through Id2. Am J Physiol Lung Cell Mol Physiol 290: L120–L126, 2006.[Abstract/Free Full Text]
  29. Janssens WJ, Verhaeghe RH. Effect of thrombin on isolated canine blood vessels. Blood Vessels 19: 126–134, 1982.[Web of Science][Medline]
  30. Joshi S, Balan P, Gurney AM. Pulmonary vasoconstrictor action of KCNQ potassium channel blockers. Respir Res 7: 31–40, 2006.[CrossRef][Medline]
  31. Kunichika N, Yu Y, Remillard CV, Platoshyn O, Zhang S, Yuan JXJ. Overexpression of TRPC1 enhances pulmonary vasoconstriction induced by capacitative Ca2+ entry. Am J Physiol Lung Cell Mol Physiol 287: L962–L969, 2004.[Abstract/Free Full Text]
  32. Launay JM, Hervé P, Peoc'h K, Tournois C, Callebert J, Nebigil CG, Etienne N, Drouet L, Humbert M, Simonneau G, Maroteaux L. Function of the serotonin 5-hydroxytryptamine 2B receptor in pulmonary hypertension. Nat Med 8: 1129–1135, 2002.[CrossRef][Web of Science][Medline]
  33. Lawrence RN, Clelland C, Beggs D, Salama FD, Dunn WR, Wilson VG. Differential role of vasoactive prostanoids in porcine and human isolated pulmonary arteries in response to endothelium-dependent relaxants. Br J Pharmacol 125: 1128–1137, 1998.[CrossRef][Web of Science][Medline]
  34. Lawrie A, Spiekerkoetter E, Martinez EC, Ambartsumian N, Sheward WJ, MacLean MR, Harmar AJ, Schmidt AM, Lukanidin E, Rabinovitch M. Interdependent serotonin transporter and receptor pathways regulate S100A4/Mts1, a gene associated with pulmonary vascular disease. Circ Res 97: 227–235, 2005.[Abstract/Free Full Text]
  35. Le Cras TD, Hardie WD, Fagan K, Whitsett JA, Korfhagen TR. Disrupted pulmonary vascular development and pulmonary hypertension in transgenic mice overexpressing transforming growth factor-{alpha}. Am J Physiol Lung Cell Mol Physiol 285: L1046–L1054, 2003.[Abstract/Free Full Text]
  36. Liu JQ, Erbynn EM, Folz RJ. Chronic hypoxia-enhanced murine pulmonary vasoconstriction: role of superoxide and gp91phox. Chest 128: 594S–596S, 2005.[CrossRef][Web of Science][Medline]
  37. Liu JQ, Folz RJ. Extracellular superoxide enhances 5-HT-induced murine pulmonary artery vasoconstriction. Am J Physiol Lung Cell Mol Physiol 287: L111–L118, 2004.[Abstract/Free Full Text]
  38. Liu JQ, Zelko IN, Erbynn EM, Sham JSK, Folz RJ. Hypoxic pulmonary hypertension: role of superoxide and NADPH oxidase (gp91phox). Am J Physiol Lung Cell Mol Physiol 290: L2–L10, 2006.[Abstract/Free Full Text]
  39. Liu LH, Paul RJ, Sutliff RL, Miller ML, Lorenz JN, Pun RYK, Duffy JJ, Doetschman T, Kimura Y, MacLennan DH, Hoying JB, Shull GE. Defective endothelium-dependent relaxation of vascular smooth muscle and endothelial cell Ca2+ signaling in mice lacking sarco(endo)plasmic reticulum Ca2+-ATPase isoform 3. J Biol Chem 272: 30538–30545, 1997.[Abstract/Free Full Text]
  40. Long L, MacLean MR, Jeffery TK, Morecroft I, Yang X, Rudarakanchana N, Southwood M, James V, Trembath RC, Morrell NW. Serotonin increases susceptibility to pulmonary hypertension in BMPR2-deficient mice. Circ Res 98: 818–827, 2006.[Abstract/Free Full Text]
  41. Lorenz JN, Arend LJ, Robitz R, Paul RJ, MacLennan AJ. Vascular dysfunction in S1P2 sphingosine 1-phosphate receptor knockout mice. Am J Physiol Regul Integr Comp Physiol 292: R440–R446, 2007.[Abstract/Free Full Text]
  42. MacLean MR, Sweeney G, Baird M, McCulloch KM, Houslay M, Morecroft I. 5-Hydroxytryptamine receptors mediating vasoconstriction in pulmonary arteries from control and pulmonary hypertensive rats. Br J Pharmacol 119: 917–930, 1996.[Web of Science][Medline]
  43. Madden JA, Vadula KS, Kurup VP. Effects of hypoxia and other vasoactive agents on pulmonary and cerebral artery smooth muscle cells. Am J Physiol Lung Cell Mol Physiol 263: L384–L393, 1992.[Abstract/Free Full Text]
  44. McDaniel SS, Platoshyn O, Wang J, Yu Y, Sweeney M, Krick S, Rubin LJ, Yuan JXJ. Capacitative Ca2+ entry in agonist-induced pulmonary vasoconstriction. Am J Physiol Lung Cell Mol Physiol 280: L870–L880, 2001.[Abstract/Free Full Text]
  45. Morecroft I, Dempsie Y, Bader M, Walther DJ, Kotnik K, Loughlin L, Nilsen M, MacLean MR. Effect of tryptophan hydroxylase 1 deficiency on the development of hypoxia-induced pulmonary hypertension. Hypertension 49: 232–236, 2007.[Abstract/Free Full Text]
  46. Ng LC, Gurney AM. Store-operated channels mediate Ca2+ influx and contraction in rat pulmonary artery. Circ Res 89: 923–929, 2001.[Abstract/Free Full Text]
  47. Ozaki M, Kawashima S, Yamashita T, Ohashi Y, Rikitake Y, Inoue N, Hirata KI, Hayashi Y, Itoh H, Yokoyama M. Reduced hypoxic pulmonary vascular remodeling by nitric oxide from the endothelium. Hypertension 37: 322–327, 2001.[Abstract/Free Full Text]
  48. Perlegas D, Xie H, Sinha S, Somlyo AV, Owens GK. ANG II type 2 receptor regulates smooth muscle growth and force generation in late fetal mouse development. Am J Physiol Heart Circ Physiol 288: H96–H102, 2005.[Abstract/Free Full Text]
  49. Rios EJ, Fallon M, Wang J, Shimoda LA. Chronic hypoxia elevates intracellular pH and activates Na+/H+ exchange in pulmonary arterial smooth muscle cells. Am J Physiol Lung Cell Mol Physiol 289: L867–L874, 2005.[Abstract/Free Full Text]
  50. Sai Y, Okamura T, Amakata Y, Toda N. Comparison of responses of canine pulmonary artery and vein to angiotensin II, bradykinin and vasopressin. Eur J Pharmacol 282: 235–241, 1995.[CrossRef][Web of Science][Medline]
  51. Said SI, Hamidi SA, Dickman KG, Szema AM, Lyubsky S, Lin RZ, Jiang YP, Chen JJ, Waschek JA, Kort S. Moderate pulmonary arterial hypertension in male mice lacking the vasoactive intestinal peptide gene. Circulation 115: 1260–1268, 2007.[Abstract/Free Full Text]
  52. Sauzeau V, Rolli-Derkinderen M, Lehoux S, Loirand G, Pacaud P. Sildenafil prevents change in RhoA expression induced by chronic hypoxia in rat pulmonary artery. Circ Res 93: 630–637, 2003.[Abstract/Free Full Text]
  53. Schmidt D, Rühlmann E, Waldeck B, Branscheid D, Luts A, Sundler F, Rabe K. The effect of the vasoactive intestinal polypeptide agonist Ro 25–1553 on induced tone in isolated human airways and pulmonary artery. Naunyn Schmiedebergs Arch Pharmacol 364: 314–320, 2001.[CrossRef][Web of Science][Medline]
  54. Seiden JE, Platoshyn O, Bakst AE, McDaniel SS, Yuan JXJ. High K+-induced membrane depolarization attenuates endothelium-dependent pulmonary vasodilation. Am J Physiol Lung Cell Mol Physiol 278: L261–L267, 2000.[Abstract/Free Full Text]
  55. Shimoda LA, Sylvester JT, Booth GM, Shimoda TH, Meeker S, Undem BJ, Sham JSK. Inhibition of voltage-gated K+ currents by endothelin-1 in human pulmonary arterial myocytes. Am J Physiol Lung Cell Mol Physiol 281: L1115–L1122, 2001.[Abstract/Free Full Text]
  56. Somlyo AP, Somlyo AV. Smooth muscle: excitation-contraction coupling, contractile regulation, and the cross-bridge cycle. Alcohol Clin Exp Res 18: 138–143, 1994.[CrossRef][Web of Science][Medline]
  57. Steudel W, Ichinose F, Huang PL, Hurford WE, Jones RC, Bevan JA, Fishman MC, Zapol WM. Pulmonary vasoconstriction and hypertension in mice with targeted disruption of the endothelial nitric oxide synthase (NOS 3) gene. Circ Res 81: 34–41, 1997.[Abstract/Free Full Text]
  58. Swafford AN Jr, Harrison-Bernard LM, Dick GM. Knockout mice reveal that the angiotensin II type 1B receptor links to smooth muscle contraction. Am J Hypertens 20: 335–337, 2007.[CrossRef][Web of Science][Medline]
  59. Vaishnav RN, Vossoughi J. Estimation of residual strains in aortic segments. In: Biomedical Engineering. II. Recent Developments, edited by Hall CW. New York: Pergammon, 1983, p. 330–333.
  60. Wanstall JC, O'Donnell SR. Endothelin and 5-hydroxytryptamine on rat pulmonary artery in pulmonary hypertension. Eur J Pharmacol 176: 159–168, 1990.[CrossRef][Web of Science][Medline]
  61. Wanstall JC, O'Donnell SR. Endothelin-induced contractions of rat pulmonary artery are not affected by drugs acting on potassium channels. J Pharm Pharmacol 43: 739–741, 1991.[Web of Science][Medline]
  62. West J, Fagan K, Steudel W, Fouty B, Lane K, Harral J, Hoedt-Miller M, Tada Y, Ozimek J, Tuder R, Rodman DM. Pulmonary hypertension in transgenic mice expressing a dominant-negative BMPRII gene in smooth muscle. Circ Res 94: 1109–1114, 2004.[Abstract/Free Full Text]
  63. Yu AY, Shimoda LA, Iyer NV, Huso DL, Sun X, McWilliams R, Beaty T, Sham JSK, Wiener CM, Sylvester JT, Semenza GL. Impaired physiological responses to chronic hypoxia in mice partially deficient for hypoxia-inducible factor 1{alpha}. J Clin Invest 103: 691–696, 1999.[Web of Science][Medline]
  64. Yuan JXJ, Aldinger AM, Juhaszova M, Wang J, Conte JV Jr, Gaine SP, Orens JB, Rubin LJ. Dysfunctional voltage-gated K+ channels in pulmonary artery smooth muscle cells of patients with primary pulmonary hypertension. Circulation 98: 1400–1406, 1998.[Abstract/Free Full Text]
  65. Yuan XJ. Voltage-gated K+ currents regulate resting membrane potential and [Ca2+]i in pulmonary arterial myocytes. Circ Res 77: 370–378, 1995.[Abstract/Free Full Text]
  66. Yuan XJ, Tod ML, Rubin LJ, Blaustein MP. Contrasting effects of hypoxia on tension in rat pulmonary and mesenteric arteries. Am J Physiol Heart Circ Physiol 259: H281–H289, 1990.[Abstract/Free Full Text]
  67. Zaidi SHE, You XM, Ciura S, Husain M, Rabinovitch M. Overexpression of the serine elastase inhibitor elafin protects transgenic mice from hypoxic pulmonary hypertension. Circulation 105: 516–521, 2002.[Abstract/Free Full Text]
  68. Zhao YJ, Wang J, Rubin LJ, Yuan XJ. Inhibition of KV and KCa channels antagonizes NO-induced relaxation in pulmonary artery. Am J Physiol Heart Circ Physiol 272: H904–H912, 1997.[Abstract/Free Full Text]
  69. Zhao YJ, Wang J, Tod ML, Rubin LJ, Yuan XJ. Pulmonary vasoconstrictor effects of prostacyclin in rats: potential role of thromboxane receptors. J Appl Physiol 81: 2595–2603, 1996.[Abstract/Free Full Text]
  70. Zheng YM, Mei QB, Wang QS, Abdullaev I, Lai FA, Xin HB, Kotlikoff M, Wang YX. Role of FKBP12.6 in hypoxia- and norepinephrine-induced Ca2+ release and contraction in pulmonary artery myocytes. Cell Calcium 35: 345–355, 2004.[CrossRef][Web of Science][Medline]
  71. Zhou Y, Chen Y, Dirksen WP, Morris M, Periasamy M. AT1b receptor predominantly mediates contractions in major mouse blood vessels. Circ Res 93: 1089–1094, 2003.[Abstract/Free Full Text]
  72. Zhou Y, Varadharaj S, Zhao X, Parinandi N, Flavahan NA, Zweier JL. Acetylcholine causes endothelium-dependent contraction of mouse arteries. Am J Physiol Heart Circ Physiol 289: H1027–H1032, 2005.[Abstract/Free Full Text]



This article has been cited by other articles:


Home page
 Am. J. Physiol. Heart Circ. Physiol.Home page
M. Xu, C. V. Remillard, B. D. Sachs, A. Makino, O. Platoshyn, W. Yao, W. H. Dillmann, K. Akassoglou, and J. X.-J. Yuan
p75 neurotrophin receptor regulates agonist-induced pulmonary vasoconstriction
Am J Physiol Heart Circ Physiol, October 1, 2008; 295(4): H1529 - H1538.
[Abstract] [Full Text] [PDF]

This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow All Versions of this Article:
294/1/H220    most recent
00968.2007v1
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in Web of Science
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Xu, M.
Right arrow Articles by Yuan, J. X.-J.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Xu, M.
Right arrow Articles by Yuan, J. X.-J.

HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
Visit Other APS Journals Online
Copyright © 2008 by the American Physiological Society.