AJP - Heart Fuel your research with LabChart
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
QUICK SEARCH:   [advanced]


     

Am J Physiol Heart Circ Physiol 282: H273-H280, 2002;
0363-6135/02 $5.00
This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
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 ISI 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 ISI Web of Science (14)
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Tolsa, J.-F.
Right arrow Articles by Raj, J. U.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Tolsa, J.-F.
Right arrow Articles by Raj, J. U.
Vol. 282, Issue 1, H273-H280, January 2002

Differential responses of newborn pulmonary arteries and veins to atrial and C-type natriuretic peptides

Jean-Francois Tolsa1, Yuansheng Gao2, Fred C. Sander2, Anne-Christine Souici1, Adrien Moessinger1, and J. Usha Raj2

1 Neonatal Research Laboratory, Division of Neonatology, Department of Pediatrics, Centre Hospitalier Universitaire Vaudois, 1011 Lausanne, Switzerland; and 2 Department of Pediatrics, Harbor-University of California Los Angeles Medical Center, Torrance, California 90509


    ABSTRACT
TOP
ABSTRACT
INTRODUCTION
MATERIALS AND METHODS
RESULTS
DISCUSSION
REFERENCES

Atrial natriuretic peptide (ANP) and C-type natriuretic peptide (CNP) are important dilators of the pulmonary circulation during the perinatal period. We compared the responses of pulmonary arteries (PA) and veins (PV) of newborn lambs to these peptides. ANP caused a greater relaxation of PA than of PV, and CNP caused a greater relaxation of PV than of PA. RIA showed that ANP induced a greater increase in cGMP content of PA than CNP. In PV, ANP and CNP caused a similar moderate increase in cGMP content. Receptor binding study showed more specific binding sites for ANP than for CNP in PA and more for CNP than for ANP in PV. Relative quantitative RT-PCR for natriuretic peptide receptor A (NPR-A) and B (NPR-B) mRNAs show that, in PA, NPR-A mRNA is more prevalent than NPR-B mRNA, whereas, in PV, NPR-B mRNA is more prevalent than NPR-A mRNA. In conclusion, in the pulmonary circulation, arteries are the major site of action for ANP, and veins are the major site for CNP. Furthermore, the differences in receptor abundance and the involvement of a cGMP-independent mechanism may contribute to the heterogeneous effects of the natriuretic peptides in PA and PV of newborn lambs.

smooth muscle; relaxation; natriuretic peptide receptor; perinatal; pulmonary circulation


    INTRODUCTION
TOP
ABSTRACT
INTRODUCTION
MATERIALS AND METHODS
RESULTS
DISCUSSION
REFERENCES

ATRIAL AND C-TYPE natriuretic peptides (ANP and CNP) are 28- and 22-amino acid peptides, respectively. ANP induces diuresis and natriuresis, whereas CNP has minimal effects on diuresis and natriuresis. Both peptides induce vasodilation. However, studies suggest that ANP is more potent in arteries, whereas CNP is more potent in veins (17, 20, 28, 48, 49). ANP is secreted primarily by atrial myocytes in response to local stretch and acts in an endocrine fashion (40). CNP acts in a paracrine fashion (15, 23) and is expressed widely in the central nervous system, with the highest concentrations found in the cerebellum. Studies show that CNP may act as a neurotransmitter to coordinate central aspects of salt and water balance and blood pressure (7, 23, 25, 39, 47). Outside the central nervous system, CNP is produced mainly by the vascular endothelium (18). Studies suggest that CNP may be released from the endothelium in response to agonists such as ACh and bradykinin (50) and various cytokines and growth factors such as transforming growth factor-alpha and tumor necrosis factor-alpha (33).

Two distinctive types of natriuretic peptide receptors, designated NPR-A and NPR-B, mediate actions of ANP and CNP, respectively. NPR-A is activated with high affinity by ANP, and CNP is a specific agonist of the NPR-B (23, 24, 27). Both NPR-A and NPR-B possess guanylyl cyclase activity. Upon binding to these receptors, ANP and CNP elevate the intracellular cGMP content, which in turn mediates the biological actions of these peptides (1, 23).

The role of ANP and CNP in the perinatal pulmonary circulation is not well established. ANP is a potent dilator of pulmonary arteries of the fetus and the newborn (28). In humans, ANP is detectable in fetal plasma. The plasma ANP level is higher in early postnatal life than in the adult (41, 42). In the pig, ANP causes relaxation of pulmonary arteries at all ages, but the relaxation is greater at 6 and 17 days of age (28). Plasma CNP levels are increased in adult patients with cor pulmonale (8), raising the possibility that CNP may be a circulating hormone involved in the regulation of cardiovascular function. In experimented animals, the administration of CNP induces vasodilation of both arteries and veins (48). In the adult rat, CNP is a slightly less potent dilator of pulmonary arteries than ANP (20). In the pig at various ages, CNP is a poor dilator of pulmonary arteries (28).

Previous studies by others and us show that, in perinatal lungs, pulmonary veins exhibit considerable vasoreactivity in response to various stimuli (2, 11, 12, 36, 37, 43, 52). Veins contribute substantially to total pulmonary vascular resistance (37, 38). More recently, it has been shown that CNP relaxed fetal ovine pulmonary veins better than pulmonary arteries (26). Responses of newborn pulmonary veins to ANP and CNP have not been well characterized. We postulate that ANP and CNP may participate differently in the regulation of pulmonary vascular tone in the neonatal period. In the present study, we have compared the responses of pulmonary arteries and veins of newborn lambs to ANP and CNP. Furthermore, the mechanisms underlying the different responses were investigated.


    MATERIALS AND METHODS
TOP
ABSTRACT
INTRODUCTION
MATERIALS AND METHODS
RESULTS
DISCUSSION
REFERENCES

Twenty-five newborn lambs (7-12 days old, either sex) from Nebeker Ranch (Lancaster, CA) were used. They were anesthetized with ketamine hydrochloride (30 mg/kg im) and killed with an overdose of pentobarbital sodium. The lungs were immediately removed, and fourth-generation pulmonary arteries and veins (outside diameter 3.0-3.5 and 2.5-3.0 mm, respectively) were dissected free of parenchyma and cut into rings (length 3 mm). In some vessels the endothelium was removed mechanically by inserting the tips of a watchmaker's forceps in the lumen of the vessel and rolling it back and forth on saline-loaded filter paper. Removal of endothelium was confirmed for each vessel ring by lack of relaxation to ACh (3 × 10-5 M; see Ref. 13).

Organ chamber study. Vessel rings were suspended in organ chambers filled with 10 ml of modified Krebs-Ringer bicarbonate solution [composition (in mM): 118.3 NaCl, 4.7 KCl, 2.5 CaCl2, 1.2 MgSO4, 1.2 KH2PO4, 25.0 NaHCO3, and 11.1 glucose] maintained at 37 ± 0.5°C and aerated with 95% O2-5% CO2 (pH = 7.4). Two stirrups passed through the lumen suspended each ring. One stirrup was anchored to the bottom of the organ chamber, and the other was connected to a strain gauge (model FT03C; Grass Instrument, Braintree, MA) to measure the isometric force (45).

At the beginning of the experiment, each vessel ring was stretched to its optimal resting tension. This was achieved by step-wise stretching, in 0.1-g increments, until the active contraction of the vessel ring to 100 mM KCl reached a plateau. The optimal resting tension of pulmonary arteries with and without endothelium was 0.29 ± 0.05 and 0.26 ± 0.04 g/mm2 cross-section area of smooth muscle (CSASM), respectively (n = 7 for each group). The optimal resting tension of pulmonary veins with and without endothelium was 0.13 ± 0.04 and 0.15 ± 0.03 g/mm2 CSASM, respectively (n = 7 for each group). The resting tension of pulmonary arteries was significantly different from that of veins (P < 0.05). However, there is no significant difference in the resting tension between vessels with and without endothelium (P > 0.05). The vessels were allowed to equilibrate at their optimal resting tension for 1 h. Next, indomethacin (10-5 M; an inhibitor of cyclooxygenase; see Ref. 46) was administered to exclude the possible involvement of endogenous prostanoids (12). Our previous study shows that there is a basal release of PGE2 and PGI2 in newborn ovine pulmonary veins without endothelium (12). Hence, an inhibition of the production of these dilator prostaglandins may contribute to the increased tone in endothelium-denuded veins caused by indomethacin. There is also a basal release of PGE2 and PGI2 in pulmonary arteries of newborn lambs. The lack of effect of indomethacin on arterial tone may be partially due to the fact that the arteries were less sensitive to PGE2 and PGI2 (12).

Effects of alpha -ANP-(1---28) (10-12 to 10-7 M), CNP-22 (10-12 to 10-7 M), and exogenous nitric oxide (10-7 M) were determined in pulmonary arteries and veins preconstricted with endothelin-1 (3 × 10-9 to 2 × 10-8 M). In some experiments, 1H-[1,2,4]oxadiazolo-[4,3-a]quinoxalin-1-one (ODQ, 3 × 10-5 M; an inhibitor of soluble guanylyl cyclase; see Ref. 14) was added to differentiate between relaxation mediated by particulate guanylyl cyclase vs. soluble guanylyl cyclase (14). To test whether or not a cGMP-independent mechanism may be involved, some vessels were pretreated with 8-bromo-cGMP (8-BrcGMP), a cell membrane-permeable analog of cGMP (29), at a concentration that causes near maximal relaxation (3 × 10-4 M; see Ref. 13). The vessels were then constricted with endothelin-1, and the effects of ANP and CNP were studied.

Determination of CSASM. The isometric tension of pulmonary arteries and veins of newborn lambs was standardized to CSASM, as described earlier (11). Briefly, the total cross-section area of vessels (CSAT) was obtained first using the following formula: CSAT = wet weight of tissue (mg) divide  density of tissue (mg/mm3) divide  optimal length of the tissue (mm). The tissue density was measured by dividing the blotted wet weight of the tissue by its volume. The volume was determined by measuring the volume of Krebs-Ringer-bicarbonate solution displaced by the vessels after placing them in a 1-ml graduated cylinder with an accuracy of 0.01 ml. The optimal length was determined with the aid of a magnifying eyepiece and a micrometer with an accuracy of 0.01 mm by measuring the distance between two stirrups passed through the lumen of the vessel ring under their optimal resting tension.

After CSAT was determined, the ratio of CSASM to CSAT (CSASM/CSAT) was obtained by counting the total area and the area occupied by smooth muscle cells on a histological transverse section of the pulmonary arteries (5 µm thick) under a microscope. The histological sections were treated with either hematoxilin and eosin stain or Van Giesson stain to differentiate between smooth muscle cells and other components. The CSASM/CSAT obtained from hematoxylin and eosin stains and those from Van Giesson staining were averaged. The mean values were multiplied by the CSAT to obtain the smooth muscle cross-sectional area of the tissue.

RIA of the intracellular content of cGMP. Rings of ovine pulmonary arteries and veins (without endothelium) were incubated in 10 ml of modified Krebs-Ringer bicarbonate solution (37°C, 95% O2-5% CO2) containing indomethacin (10-5 M) and isobutyl methylxanthine (10-3 M). These inhibitors were used to eliminate the involvement of cyclooxygenase products and phosphodiesterases, respectively (12, 34). In some experiments, ODQ (3 × 10-5 M) was used to determine whether or not soluble guanylyl cyclase was involved (14).

After 45 min of equilibration, ANP (10-7 M), CNP (10-7 M) or nitric oxide (10-7 M) was added to the incubation vials. Two minutes after the administration of ANP or CNP and 1 min after nitric oxide was added, the tissues were freeze-clamped rapidly and thawed in TCA (6%). Preliminary studies showed that the maximal accumulation of cGMP occurred at 2 min in response to ANP and CNP and at 1 min in response to nitric oxide. The tissues were then homogenized in glass with a motor-driven Teflon pestle, sonicated for 5 s, and centrifuged at 13,000 g for 15 min. The supernatant was extracted with 4 vol of water-saturated diethyl ether and lyophilized; the pellets were weighed. The lyophilized samples were resuspended in 0.5 ml of sodium acetate buffer (0.05 M, pH 6.2), and their intracellular content of cGMP was determined using a cGMP kit (Biomedical Technologies, Stoughton, MA). The content of cGMP is expressed as picomoles per milligram protein. The protein concentrations of the vessels were determined by the Bradford method using BSA as the standard (6).

Receptor binding. Receptor bindings for ANP and CNP were determined using a method similar to that described by Perreault et al. (35). The membrane preparations of pulmonary arteries and veins (without endothelium) were obtained by homogenizing the tissues in 5 vol of ice-cold buffer containing 50 mM Tris · HCl (pH 7.4), 2 mM dithiothreitol (DTT), 10 mM EDTA, 10 µg/ml leupeptin, 10 µg/ml antipain, 10 µg/ml pepstatin, 10 µg/ml aprotinin, and 0.5 mM phenylmethylsulfonyl fluoride (PMSF). The homogenate was centrifuged at 500 g for 10 min at 4°C. The supernatant was centrifuged at 100,000 g for 1 h at 4°C, and the resulting pellets were resuspended in a buffer similar to that used for tissue homogenization with the addition of 0.2% Triton X-100. Protein concentrations of the preparations were assessed by the Bradford method using BSA as the standard (6).

Binding assay was carried out in an assay mixture (total volume: 100 µl) containing 50 mM Tris · HCl (pH 7.4), 2 mM DTT, 10 mM EDTA, 10 µg/ml leupeptin, 10 µg/ml antipain, 10 µg/ml pepstatin, 10 µg/ml aprotinin, 0.5 mM PMSF, 10 mg/ml BSA, 5 mM MgCl2, 10-500 pM 125I-labeled alpha -ANP-(1---28) (sp act 1,189 Ci/mmol; Peninsula Laboratories, Belmont, CA) or 10-500 pM 125I-labeled [Tyro]CNP-22 (sp act 2,226 Ci/mmol; Peninsula Laboratories), and 30 µg membrane protein. Triplicate samples were incubated for 60 min at 30°C. At the end of the incubation period, the bound tracer was separated from the free tracer by rapid filtration through 1% polyethylenamine-treated Whatman GF/C glass filters. Filters were washed with 3 ml of cold Tris · HCl buffer (50 mM). The radioactivity associated with the filters was determined in an automatic gamma -counter (model 1470; Wallac, Gaithersburg, MD). Nonspecific binding for ANP and CNP was determined in the presence of 1 µM of unlabeled alpha -ANP-(1---28) or unlabeled [Tyro]CNP-22, respectively. Specific binding was calculated as total binding minus nonspecific binding.

Relative quantitative RT-PCR for NPR-A and NPR-B mRNAs. Total RNA was extracted from pulmonary arteries and veins using Trizol reagent (Life Technologies, Grand Island, NY) according to the manufacturer's protocol. The mRNA reverse transcription was started by adding 2 µl RNA to a 11.5 µl buffer containing 250 ng random hexamers and 10 unit RNase inhibitor (Life Technologies), incubating at 70°C for 10 min, and quick chilling on ice. Next, 4.0 µl of 5× first strand buffer (Life Technologies), 2.0 µl DTT (0.1 M), 1.0 µl dNTP (10 mM), 0.5 µl RNase inhibitor (20 U/µl), and 1 ml Moloney leukemia virus reverse transcriptase (200 U/µl; Life Technologies) were added. The reaction mixture was incubated at 42°C for 1 h and at 90°C for 10 min. The yielded cDNA products were amplified by PCR with sense and antisense primers.

The sense and antisense primers for NPR-A were 5'-AAGAGCCTGATAATCCTGAGTACT-3' (1302-1325: accession no. NM_12613) and 5'-TTGCAGGCTGGGTCCTCATTGTCA-3' (1752-1729: accession mo. NM_12613), respectively. The sense and antisense primers for NPR-B were 5'-AACGGGCGCATTGTGTATATCTGCGGC-3' (730-756: accession no. M26896) and 5'-TTATCACAGGATGGGTCGTCCAAGTCA-3' (1421-1395: accession no. M26896), respectively (19, 23).

Relative quantitative (RQ) RT-PCR was performed on a Stratagene (La Jolla, CA) thermal cycler (RoboCycler Gradient 96) according to a protocol by Ambion (Austin, TX). Briefly, a 50-µl reaction mixture contains 5 µl 10× ThermalAce Buffer (Invitrogen, Carlsbad, CA), 1.0 µl 50× dNTPs (10 mM each; Invitrogen), 20 units ThermalAce DNA Polymerase (Invitrogen), 2.0 µl cDNA, 25 pM each for NPR-A sense and antisense and for NPR-B sense and antisense, 1.0 µl Universal 18S primer, and 1.5 µl 18S competimers (Ambion). The mixture was initially subjected to heating for 2 min at 94°C and then 31 cycles of 30 s at 94°C, 45 s at 55°C, and 60 s at 72°C. Preliminary studies showed that 31 cycles were in the linear range of the PCR reaction and that the ratio for 18S primer to 18S competimer produced similar yields for the 18S internal standard, NPR-A mRNA from pulmonary arteries, and NPR-B mRNA from pulmonary veins. PCR products were separated on 1% agarose gels (containing 0.08% ethidium bromide) and quantified by densitometry using an Eagle Eye II Still Video System (Stratagene). The quantities of mRNA for NPR-A and NPR-B were expressed as relative units to the 18S used.

Preparation of nitric oxide. A gas bulb sealed with a silicone rubber injection septum was filled with nitric oxide from a cylinder (Union Carbide, Chicago, IL). An appropriate volume (2.5 ml) was removed with a syringe and injected in another gas bulb filled with 250 ml of distilled water, which had been gassed with helium for over 3 h, giving stock solutions of nitric oxide of 4.2 × 10-4 M. The concentrations of nitric oxide in the stock solutions were determined by indirectly measuring the nitrate, which was converted from nitric oxide using an assay kit (Cayman Chemical, Ann Arbor, MI; see Ref. 22). The final concentrations of nitric oxide in the organ chambers were calculated based on the ratio of the dilution.

Drugs. The following drugs were used (unless otherwise specified, all were obtained from Sigma, St. Louis, MO): alpha -ANP-(1---28) (Peninsula Laboratories), 8-BrcGMP, CNP-22 (Peninsula Laboratories), endothelin-1 (American Peptide, Sunnyvale, CA), indomethacin, isobutyl methylxanthine, and ODQ. ODQ was dissolved in DMSO (final concentrations <0.2%). Preliminary experiments showed that DMSO at the concentration used had no effect on contraction to endothelin-1 and had no effect on relaxation induced by ANP and CNP in pulmonary vessels of newborn lambs. Indomethacin (10-5 M) was prepared in equal molar Na2CO3. This concentration of Na2CO3 did not significantly affect the pH of the solution in the organ chamber. The other drugs were prepared using distilled water.

Data analyses. Data are shown as means ± SE. When mean values of two groups were compared, Student's t-test for unpaired observations was used. When the mean values of the same group before and after stimulation were compared, Student's t-test for paired observations was used. The comparison of the mean values of more than two groups was made using the one-way ANOVA test and the Student-Newman-Keuls test for post hoc testing of multiple comparisons. All analyses were performed using a commercially available statistics package (SigmaStat; Jandel Scientific, San Rafael, CA). Statistical significance was accepted when the P value (two tailed) was <0.05. In all experiments, n represents the number of animals.


    RESULTS
TOP
ABSTRACT
INTRODUCTION
MATERIALS AND METHODS
RESULTS
DISCUSSION
REFERENCES

Morphological data. Morphological data of pulmonary arteries and veins of newborn lambs are shown in Table 1. The wet weight and optimal length of the rings of pulmonary arteries and veins were significantly different. The density of these tissues was comparable. The CSAT of pulmonary arteries was significantly greater than that of pulmonary veins. The CSASM-to-CSAT ratio was significantly different between pulmonary arteries and veins. However, there was no significant difference in these values between vessels with and without endothelium.

                              
View this table:
[in this window]
[in a new window]
  		Table 1.   Morphological data of pulmonary arteries and veins of newborn lambs

Organ chamber studies. Experiments were carried out in the presence of indomethacin to exclude the involvement of endogenous prostaglandins (13). Under basal conditions, indomethacin (10-5 M) had no effect on pulmonary arteries but caused a greater increase in the resting tone of pulmonary veins without endothelium than that of pulmonary veins with endothelium [0.39 ± 0.07 g/mm2 CSASM (n = 13) vs. 0.14 ± 0.06 g/mm2 CSASM (n = 6); P < 0.05]. Before testing the effect of various vasodilators, pulmonary arteries and veins were constricted with endothelin-1 (3 × 10-9 to 2 × 10-8 M) to a similar tension (Table 2). At the concentrations of endothelin-1 used, the arteries with and without endothelium contracted to 73.9 ± 8.5 and 72.6 ± 6.1% of their maximal responses, respectively (n = 6 for each group); the veins with and without endothelium contracted to 82.1 ± 6.5 and 75.3 ± 8.1% of their maximal responses, respectively (n = 6 for each group).

                              
View this table:
[in this window]
[in a new window]
  		Table 2.   Tension in pulmonary arteries and veins increased by endothelin-1 before determination of relaxing effects of ANP and CNP

ANP and CNP induced concentration-dependent relaxations of pulmonary arteries and veins. ANP-induced relaxation was greater in arteries than in veins, whereas CNP-induced relaxation was greater in veins than in arteries, with or without endothelium (Fig. 1).


View larger version (25K):
[in this window]
[in a new window]
  		Fig. 1.   Relaxation of pulmonary arteries (PA) and veins (PV) of newborn lambs with endothelium (E+) or without endothelium (E-) induced by atrial natriuretic peptide (ANP; A) and C-type natriuretic peptide (CNP; B). Tissues were preconstricted to a similar tension with endothelin-1 (3 × 10-9 to 6 × 10-9 M). Data are shown as means ± SE; n = 7 animals for each group. *Significant difference between PA and PV (P < 0.05).

In vessels without endothelium, nitric oxide (10-7 M) induced a greater relaxation of pulmonary veins than that of arteries. Relaxation to nitric oxide was inhibited by ODQ (3 × 10-5 M), an inhibitor of soluble guanylyl cyclase (14). In contrast, relaxation induced by ANP (10-7 M) or CNP (10-7 M) was not affected significantly by ODQ (Fig. 2). In some experiments, the effects of ANP, CNP, and nitric oxide were examined in pulmonary vessels without endothelium pretreated with 8-BrcGMP (3 × 10-4 M). In the presence of 8-BrcGMP, a cell membrane-permeable analog of cGMP (29), higher concentrations of endothelin-1 (10-8 to 2 × 10-8 M) were used to raise the vessel tension to a level similar to that of control vessels (Table 3). After treatment with 8-BrcGMP, relaxation of pulmonary arteries induced by ANP (10-7 M), CNP (10-7 M), and nitric oxide (10-7 M) was attenuated by 58.7 ± 3.6, 26.3 ± 2.1, and 83.4 ± 5.1%, respectively (n = 6 for each group; Fig. 2). In pulmonary veins, treatment with 8-BrcGMP attenuated relaxation induced by ANP (10-7 M), CNP (10-7 M), and nitric oxide (10-7 M) by 47.9 ± 3.0, 20.7 ± 2.6, and 68.7 ± 4.3%, respectively (n = 6 for each group). In comparison, treatment with 8-Br-cGMP attenuated relaxation induced by nitric oxide to a greater extent than that induced by ANP and attenuated the relaxation induced by CNP the least (P < 0.05; Fig. 2).


View larger version (31K):
[in this window]
[in a new window]
  		Fig. 2.   Relaxation of PA (A) and PV (B) without endothelium of newborn lambs induced by ANP (10-7 M), CNP (10-7 M), and nitric oxide (10-7 M) under control conditions, in the presence of 1H-[1,2,4]oxadiazolo-[4,3-a]quinoxalin-1-one (ODQ; 3 × 10-5 M), or in the presence of 8-bromo-cGMP (8-BrcGMP; 3 × 10-4 M). Vessels were preconstricted to a similar tension with endothelin-1 (3 × 10-9 to 2 × 10-8 M). Data are shown as means ± SE; n = 6 for each group. *Significantly different from control (P < 0.05).


                              
View this table:
[in this window]
[in a new window]
  		Table 3.   Tension in pulmonary arteries and veins increased by endothelin-1 before determining the effects of ODQ and 8-BrcGMP on relaxing effects induced by ANP, CNP, and nitric oxide

cGMP. The measurement of cGMP was performed in vessels without endothelium. Under basal conditions, the intracellular level of cGMP of pulmonary arteries (0.96 ± 0.33 pmol/mg protein; n = 7) was not significantly different from that of pulmonary veins (1.02 ± 0.35 pmol/mg protein; n = 7, P > 0.05). In pulmonary arteries, ANP (10-7 M) caused a greater increase in cGMP content than CNP (10-7 M) or nitric oxide (10-7 M). In veins, both ANP and CNP caused a similar, moderate increase in cGMP content; the increase was significantly less than that induced by nitric oxide (10-7 M). The effects of ANP and CNP on cGMP content were not significantly affected by ODQ (3 × 10-5 M). The effect of nitric oxide was inhibited by ODQ (3 × 10-5 M; Fig. 3).


View larger version (16K):
[in this window]
[in a new window]
  		Fig. 3.   Changes in the intracellular cGMP content of PA and PV of newborn lambs after treatment with ANP (10-7 M; n = 7), CNP (10-7 M; n = 7), and nitric oxide (10-7 M; n = 8) under control conditions or in the presence of ODQ (3 × 10-5 M). Data are shown as means ± SE. *Significantly different from vessels treated with ANP; dagger significantly different from vessels treated with ANP or CNP; Dagger significantly different from control (P < 0.05).

ANP and CNP receptors. After a 60-min incubation with 125I-ANP-(1---28) (10-500 pM) or 125I-CNP (10-500 pM) at 30°C, the membrane preparations of pulmonary arteries showed a greater specific binding to 125I-ANP than those of veins [maximal binding (Bmax) 116.6 ± 8.9 vs. 69.7 ± 6.3 fmol/mg protein; n = 7, P < 0.05]. In contrast, the membrane preparations of pulmonary veins showed greater specific binding to 125I-CNP than that of arteries (Bmax 102.8 ± 4.2 vs. 57.7 ± 3.1 fmol/mg protein; n = 7, P < 0.05). The equilibrium dissociation constant value (KD) for ANP binding receptors was 268.9 ± 53.0 and 242.4 ± 59.0 pM for pulmonary arteries and veins, respectively. The KD values for CNP was 211.4 ± 32.2 and 236.5 ± 25.9 pM for pulmonary arteries and veins, respectively. There is no significant difference between these KD values (n = 7 for each group, P > 0.05; Fig. 4).


View larger version (23K):
[in this window]
[in a new window]
  		Fig. 4.   Specific binding of 125I-ANP (A) and 125I-CNP (B) to membrane preparations of PA and PV of newborn lambs. Data are shown as means ± SE; n = 7 for each group.

NPR-A and NPR-B mRNAs. RQ RT-PCR yielded three distinctive bands corresponding to the predicted sizes for mRNA fragments of NPR-B, NPR-A, and the 18S internal standards (691, 450, and 315 bp, respectively) according to the base pair ladders. Pulmonary arteries showed a greater content of NPR-A mRNA than that of NPR-B mRNA (relative density to the 18S: 1.46 ± 0.10 vs. 0.97 ± 0.11; n = 6, P < 0.05), whereas pulmonary veins showed a greater content of NPR-B mRNA than that of NPR-A mRNA (relative density to the 18S: 1.83 ± 0.15 vs. 1.07 ± 0.11; n = 6, P < 0.05; Fig. 5).


View larger version (46K):
[in this window]
[in a new window]
  		Fig. 5.   Detection of natriuretic peptide receptor type A (NPR-A) and type B (NPR-B) mRNAs by relative quantitative RT-PCR. 18S rRNA (18S) is shown as an internal standard.


    DISCUSSION
TOP
ABSTRACT
INTRODUCTION
MATERIALS AND METHODS
RESULTS
DISCUSSION
REFERENCES

In the present study, ANP caused greater relaxation of pulmonary arteries of newborn lambs than CNP. This is consistent with previous results reported in pulmonary arteries of piglets (28) and pulmonary arteries of adult rats (20). In bovine, atriopeptin II, a synthetic fragment of ANP, causes relaxation of pulmonary arteries but not of veins (17). Our present study showed that ANP caused less relaxation of pulmonary veins than that of arteries. Thus pulmonary arteries may be the major site of action of ANP in the lung. It is interesting to note that ANP caused greater relaxation of the pulmonary arteries of newborn lambs than nitric oxide at an equal concentration. Considering that nitric oxide or nitric oxide donors are less potent dilators of pulmonary arteries than those of veins in perinatal lambs, adult pigs, and cows (5, 10, 13, 17, 43), it is possible that ANP may play a more important role in modulating pulmonary arterial activity than previously thought, at least in certain species.

Our present study demonstrates for the first time that CNP is a potent dilator of newborn pulmonary veins, greater than that of arteries. CNP caused pulmonary veins to relax at concentrations as low as 3 × 10-11 M. In fetal ovine pulmonary veins, CNP has recently been shown to be a more potent dilator than ANP (26). However, ANP and CNP were equally potent in relaxing fetal pulmonary arteries (26). This is different from our results obtained in newborn lambs and from results obtained in rat pulmonary arteries (20) and in newborn porcine pulmonary arteries (28). In porcine pulmonary arteries, there is a maturational increase in ANP-induced relaxation when comparing vessels of fetus vs. vessels of newborns of 6 and 17 days. However, in vessels of all these groups, relaxation to CNP was <5% (28). Thus a difference in maturational change between ANP and CNP may contribute to the different findings between our results from pulmonary arteries of the newborn lambs vs. those from the fetal lambs. This suggests also that CNP may be of physiological importance in the modulation of pulmonary venous tone in the fetus and in the newborn.

In contrast to ANP, which is a circulating hormone released mainly from the heart in response to stretching and other stimuli, CNP is released locally in various tissues, including vascular endothelial cells (1, 23, 31, 44). In bovine aortic endothelial cells, the synthesis and release of CNP is stimulated by ANP and brain natriuretic peptides (32). If this is the case in lungs, ANP may cause endothelium-dependent relaxation of pulmonary vessels through the release of CNP. Our data show that relaxations of pulmonary vessels with endothelium induced by ANP and CNP are not significantly different from those of vessels without endothelium (Fig. 1). Likewise, in bovine and porcine pulmonary arteries (17, 28), rabbit aorta (51), and canine renal arteries (48), relaxations induced by ANP or ANP fragments are comparable between vessels with or without endothelium. CNP causes relaxation of intact canine saphenous arteries to a similar extent as that of endothelium-denuded vessels (48). Our present results are in line with these studies. In canine renal, saphenous, and femoral veins, CNP causes greater relaxation in vessels without endothelium than that of vessels with endothelium (48). Hence, the possibility that the endothelium is a source of ANP or CNP in response to these natriuretic peptides and affects vascular tone may not be a general phenomenon. In porcine coronary arteries, CNP induces endothelium- and nitric oxide-independent hyperpolarization and relaxation (4). In bovine aortic endothelial cells, shear stress induces the release of CNP (53). The underlying mechanism of CNP-induced relaxation of pulmonary vessels is not clear and remains to be determined.

Natriuretic peptides and nitric oxide cause vasodilation by elevating the intracellular content of cGMP after stimulation of particulate and soluble guanylyl cyclase, respectively (23). In the present study, the relaxation and increase in cGMP of pulmonary vessels induced by nitric oxide, but not that induced by ANP and CNP, was inhibited by ODQ, an inhibitor of soluble guanylyl cyclase (14). Thus particulate but not soluble guanylyl cyclase is involved in the responses of pulmonary vessels induced by ANP and CNP. In pulmonary arteries of the newborn lambs, the greater relaxation induced by ANP compared with that induced by CNP was accompanied by a greater increase in cGMP content. In veins, although CNP induced a markedly larger relaxation than ANP, the increase in cGMP induced by CNP was moderate and similar to that induced by ANP. This would suggest that relaxation induced by CNP is less dependent on cGMP than that induced by ANP. In our study, relaxation induced by ANP and CNP was also tested in vessels pretreated with 8-BrcGMP at a concentration that we have previously shown to induce near maximal relaxation (3 × 10-4 M; see Ref. 13). This was done so that any further increase in cGMP content induced by ANP or CNP would not cause any further relaxation. As expected, under these conditions, relaxation to nitric oxide was largely attenuated. However, relaxation to CNP was less attenuated than that induced by ANP. These results suggest that a cGMP-independent mechanism plays a larger role in mediating relaxation to CNP than to ANP. In human kidney epithelial cells, it has been reported that CNP depolarizes the membrane potential by increasing K+ conductance via a cGMP-independent mechanism (16). In studies suggesting that ANP is more potent in arteries and CNP is more potent in veins, vessels were preconstricted with different agonists (17, 20, 26, 28, 48, 49). Therefore, it is unlikely that these phenomenon depend on the constrictor used.

The action of ANP and CNP occurs after binding to their respective receptors, namely NPR-A and NPR-B (23, 24, 27). In newborn pig lungs, it has been reported that there are more NPR-A receptors in pulmonary arteries than in veins (35). In our study, the affinity of the receptors to ANP and CNP, judged by the KD values, was similar between pulmonary arteries and veins. However, there were more specific binding sites for ANP in pulmonary arteries than in veins. For CNP, there were more specific binding sites in pulmonary veins than in arteries. Thus the greater abundance of NPR-A in arteries than in veins and the greater abundance of NPR-B in veins than in arteries may be at least partially responsible for the differential relaxation of these two types of vessel induced by ANP and CNP. Furthermore, RQ RT-PCR for NPR-A and NPR-B mRNAs show that in pulmonary arteries NPR-A mRNA is more prevalent than NPR-B mRNA, whereas in the veins NPR-B mRNA is more prevalent than NPR-A mRNA. These results provide further evidence that a difference in NPR-A and NPR-B receptor abundance in part contributes to the segmental differences in responses to ANP and CNP.

Endothelins are important modulators of pulmonary vasoactivity and have been implicated in pulmonary hypertension of various pathological conditions (3). Natriuretic peptides play an important role in modulating the pulmonary circulation of all ages under both physiological and pathological conditions (9, 20, 21, 28, 30, 31, 36). In the present study, we have demonstrated that, in newborn ovine pulmonary vessels that were preconstricted with endothelin-1, ANP is a potent dilator of pulmonary arteries, whereas CNP is a potent dilator of pulmonary veins. Moreover, ANP is more potent than nitric oxide in relaxing the newborn ovine pulmonary arteries. These data strongly suggest an important role for ANP and CNP in the perinatal pulmonary reactivity under physiological and pathological conditions, and the differential response of vessel types may be of therapeutic implications. If these characteristics are true in humans as well, they could be of therapeutic benefit. For instance, a combination of ANP and CNP would cause better vasodilation of the entire pulmonary vascular tree, and thus more effectively reduce pulmonary hypertension, than either peptide alone. In pulmonary edema, however, CNP alone would be more preferable as it mainly acts on pulmonary veins. Our present study suggests that a difference in receptor abundance and a difference in the involvement of a cGMP-independent relaxation may contribute to the heterogeneity in the responses of pulmonary arteries and veins to ANP and CNP. The mechanisms underlying the cGMP-independent action remain to be determined.


    ACKNOWLEDGEMENTS

We thank Marry Lee Ryba for secretarial assistance.


    FOOTNOTES

This study was supported by a grant from the Emma Mushamp Foundation, Switzerland, and National Heart, Lung, and Blood Institute Grant HL-59435.

Address for reprint requests and other correspondence: J.-F. Tolsa, Division of Neonatology, Dept. of Pediatrics, Univ. Hospital CHUV, 1011 Lausanne, Switzerland (E-mail: Jean-Francois.Tolsa{at}chuv.hospvd.ch).

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.

Received 12 January 2001; accepted in final form 4 September 2001.


    REFERENCES
TOP
ABSTRACT
INTRODUCTION
MATERIALS AND METHODS
RESULTS
DISCUSSION
REFERENCES

1.   Anand-Srivastava, MB, and Trachte GJ. Atrial natriuretic factor receptors and signal transduction mechanisms. Pharmacol Rev 45: 455-497, 1993[ISI][Medline].

2.   Arrigoni, FI, Hislop AA, Haworth SG, and Mitchell JA. Newborn intrapulmonary veins are more reactive than arteries in normal and hypertensive piglets. Am J Physiol Lung Cell Mol Physiol 277: L887-L892, 1999[Abstract/Free Full Text].

3.   Barnes, PJ, and Liu SF. Regulation of pulmonary vascular tone. Pharmacol Rev 47: 87-131, 1995[ISI][Medline].

4.   Barton, M, Beny JL, D'Uscio LV, Wyss T, Noll G, and Luscher TF. Endothelium-independent relaxation and hyperpolarization to C-type natriuretic peptide in porcine coronary arteries. J Cardiovasc Pharmacol 31: 377-383, 1998[ISI][Medline].

5.   Bina, S, Hart JL, Sei Y, and Muldoon SM. Factors contributing to differences in the regulation of cGMP in isolated porcine pulmonary vessels. Eur J Pharmacol 351: 253-260, 1998[ISI][Medline].

6.   Bradford, MM. A rapid and sensitive method for the quantitation of microgram quantities of protein utilizing the principle of protein-dye binding. Anal Biochem 72: 248-254, 1976[ISI][Medline].

7.   Cameron, VA, Cumming SA, Espiner EA, Nicholls G, and Richards M. C-type natriuretic peptide expression in olfactory regions of rat brain is modulated by acute water deprivation, salt loading and central angiotensin II. Neuroendocrinology 73: 46-53, 2001[ISI][Medline].

8.   Cargill, RI, Barr CS, Coutie WJ, Struthers AD, and Lipworth BJ. C-type natriuretic peptide levels in cor pulmonale and in congestive heart failure. Thorax 49: 1247-1249, 1994[Abstract].

9.   Cargill, RI, and Lipworth BJ. Pulmonary vasorelaxant activity of atrial natriuretic peptide and brain natriuretic peptide in humans. Thorax 50: 183-185, 1995[Abstract].

10.   Feletou, M, Girard V, and Canet E. Different involvement of nitric oxide in endothelium-dependent relaxation of porcine pulmonary artery and vein: influence of hypoxia. J Cardiovasc Pharmacol 25: 665-673, 1995[ISI][Medline].

11.   Gao, Y, Tolsa JF, and Raj JU. Heterogeneity in endothelium-derived nitric oxide-mediated relaxation of different sized pulmonary arteries of newborn lambs. Pediatr Res 44: 723-729, 1998[ISI][Medline].

12.   Gao, Y, Zhou H, Ibe BO, and Raj JU. Prostaglandins E2 and I2 cause greater relaxations in pulmonary veins than in arteries of newborn lambs. J Appl Physiol 81: 2534-2539, 1996[Abstract/Free Full Text].

13.   Gao, Y, Zhou H, and Raj JU. Endothelium-derived nitric oxide plays a larger role in pulmonary veins than in arteries of newborn lambs. Circ Res 76: 559-565, 1995[Abstract/Free Full Text].

14.   Garthwaite, J, Southam E, Boulton CL, Nielsen EB, Schmidt K, and Mayer B. Potent and selective inhibition of nitric oxide-sensitive guanylyl cyclase by 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one. Mol Pharmacol 48: 184-188, 1995[Abstract].

15.   Gutkowska, J, and Nemer M. Structure, expression, and function of atrial natriuretic factor in extraatrial tissues. Endocr Rev 10: 519-536, 1989[ISI][Medline].

16.   Hirsch, JR, Meyer M, Magert HJ, Forssmann WG, Mollerup S, Herter P, Weber G, Cermak R, Ankorina-Stark I, Schlatter E, and Kruhoffer M. cGMP-dependent and -independent inhibition of a K+ conductance by natriuretic peptides: molecular and functional studies in human proximal tubule cells. J Am Soc Nephrol 10: 472-480, 1999[Abstract/Free Full Text].

17.   Ignarro, LJ, Wood KS, Harbison RG, and Kadowitz PJ. Atriopeptin II relaxes and elevates cGMP in bovine pulmonary artery but not vein. J Appl Physiol 60: 1128-1133, 1986[Abstract/Free Full Text].

18.   Jamison, RL, Canaan-Kuhl S, and Pratt R. The natriuretic peptides and their receptors. Am J Kidney Dis 20: 519-530, 1992[ISI][Medline].

19.   Kim, SZ, Kim HS, Lee KS, Lee SJ, Seul KH, Koh GY, Cho KW, and Kim SH. Coexistence of C-type natriuretic peptide and atrial natriuretic peptide systems in the bovine cornea. Invest Ophthalmol Vis Sci 41: 2671-2677, 2000[Abstract/Free Full Text].

20.   Klinger, JR, Siddiq FM, Swift RA, Jackson C, Pietras L, Warburton RR, Alia C, and Hill NS. C-type natriuretic peptide expression and pulmonary vasodilation in hypoxia-adapted rats. Am J Physiol Lung Cell Mol Physiol 275: L645-L652, 1998[Abstract/Free Full Text].

21.   Klinger, JR, Warburton RR, Pietras LA, Smithies O, Swift R, and Hill NS. Genetic disruption of atrial natriuretic peptide causes pulmonary hypertension in normoxic and hypoxic mice. Am J Physiol Lung Cell Mol Physiol 276: L868-L874, 1999[Abstract/Free Full Text].

22.   Kolber, KA, Gao Y, and Raj JU. Maturational changes in endothelium-derived nitric oxide-mediated relaxation of ovine pulmonary arteries. Biol Neonate 77: 123-130, 2000[ISI][Medline].

23.   Koller, KJ, and Goeddel DV. Molecular biology of the natriuretic peptides and their receptors. Circulation 86: 1081-1088, 1992[Abstract/Free Full Text].

24.   Koller, KJ, Lowe DG, Bennett GL, Minamino N, Kangawa K, Matsuo H, and Goeddel DV. Selective activation of the B natriuretic peptide receptor by C-type natriuretic peptide (CNP). Science 252: 120-123, 1991[Abstract/Free Full Text].

25.   Komatsu, Y, Nakao K, Suga S, Ogawa Y, Mukoyama M, Arai H, Shirakami G, Hosoda K, Nakagawa O, and Hama N. C-type natriuretic peptide (CNP) in rats and humans. Endocrinology 129: 1104-1106, 1991[Abstract].

26.   Lakshminrusimha, S, D'Angelis CA, Russell JA, Nielsen LC, Gugino SF, Nickerson PA, and Steinhorn RH. C-type natriuretic peptide system in fetal ovine pulmonary vasculature. Am J Physiol Lung Cell Mol Physiol 281: L361-L368, 2001[Abstract/Free Full Text].

27.   Marquis, M, Fenrick R, Pedro L, Bouvier M, and De Lean A. Comparative binding study of rat natriuretic peptide receptor-A. Mol Cell Biochem 194: 23-30, 1999[ISI][Medline].

28.   Matsushita, T, Hislop AA, Boels PJ, Deutsch J, and Haworth SG. Changes in ANP responsiveness of normal and hypertensive porcine intrapulmonary arteries during maturation. Pediatr Res 46: 411-418, 1999[ISI][Medline].

29.   Meyer, RB, Jr, and Miller JP. Analogs of cyclic AMP and cyclic GMP: general methods of synthesis and the relationship of structure to enzymic activity. Life Sci 14: 1019-1040, 1974[ISI][Medline].

30.   Muramatsu, M, Tyler RC, Gutkowska J, Klinger JR, Hill NS, Rodman DM, and McMurtry IF. Atrial natriuretic peptide accounts for increased cGMP in hypoxia-induced hypertensive rat lungs. Am J Physiol Lung Cell Mol Physiol 272: L1126-L1132, 1997[Abstract/Free Full Text].

31.   Nakanishi, K, Tajima F, Itoh H, Nakata Y, Hama N, Nakagawa O, Nakao K, Kawai T, Torikata C, Suga T, Takishima K, Aurues T, and Ikeda T. Expression of C-type natriuretic peptide during development of rat lung. Am J Physiol Lung Cell Mol Physiol 277: L996-L1002, 1999[Abstract/Free Full Text].

32.   Nazario, B, Hu RM, Pedram A, Prins B, and Levin ER. Atrial and brain natriuretic peptides stimulate the production and secretion of C-type natriuretic peptide from bovine aortic endothelial cells. J Clin Invest 95: 1151-1157, 1995.

33.   Ogawa, Y, Itoh H, and Nakao K. Molecular biology and biochemistry of natriuretic peptide family. Clin Exp Pharmacol Physiol 22: 49-53, 1995[ISI][Medline].

34.   Okogbule-Wonodi, AC, Ibe BO, Yue BW, Hsu S, and Raj JU. Phosphodiesterase activity in intrapulmonary arteries and veins of perinatal lambs. Mol Genet Metab 65: 229-237, 1998[ISI][Medline].

35.   Perreault, T, Baribeau J, and Gutkowska J. ANF system in the newborn piglet pulmonary vessels. J Cardiovasc Pharmacol 29: 740-746, 1997[ISI][Medline].

36.   Raj, JU, and Anderson J. Pulmonary venous responses to thromboxane A2 analogue and atrial natriuretic peptide in lambs. Circ Res 66: 496-502, 1990[Abstract/Free Full Text].

37.   Raj, JU, and Chen P. Micropuncture measurement of microvascular pressures in isolated lamb lungs during hypoxia. Circ Res 59: 398-404, 1986[Abstract/Free Full Text].

38.   Raj, JU, and Chen P. Microvascular pressures measured by micropuncture in isolated perfused lamb lungs. J Appl Physiol 61: 2194-2201, 1986[Abstract/Free Full Text].

39.   Rosenzweig, A, and Seidman CE. Atrial natriuretic factor and related peptide hormones. Annu Rev Biochem 60: 229-255, 1991[ISI][Medline].

40.   Ruskoaho, H. Atrial natriuretic peptide: synthesis, release, and metabolism. Pharmacol Rev 44: 479-602, 1992[ISI][Medline].

41.   Semmekrot, B, and Guignard JP. Atrial natriuretic peptide during early human development. Biol Neonate 60: 341-349, 1991[ISI][Medline].

42.   Smith, FG, Sato T, Varille VA, and Robillard JE. Atrial natriuretic factor during fetal and postnatal life: a review. J Dev Physiol 12: 55-62, 1989[ISI][Medline].

43.   Steinhorn, RH, Morin FC, III, Gugino SF, Giese EC, and Russell JA. Developmental differences in endothelium-dependent responses in isolated ovine pulmonary arteries and veins. Am J Physiol Heart Circ Physiol 264: H2162-H2167, 1993[Abstract/Free Full Text].

44.   Thibault, G, Amiri F, and Garcia R. Regulation of natriuretic peptide secretion by the heart. Annu Rev Physiol 61: 193-217, 1999[ISI][Medline].

45.   Tolsa, JF, Gao Y, and Raj JU. Developmental change in magnesium sulfate-induced relaxation of rabbit pulmonary arteries. J Appl Physiol 87: 1589-1594, 1999[Abstract/Free Full Text].

46.   Vane, JR. Inhibitors of prostaglandin, prostacyclin, and thromboxane synthesis. Adv Prostaglandin Thromboxane Res 4: 27-44, 1978[Medline].

47.   Vatta, MS, Presas MF, Bianciotti LG, Rodriguez-Fermepin M, Ambros R, and Fernandez BE. B and C types natriuretic peptides modify norepinephrine uptake and release in the rat adrenal medulla. Peptides 18: 1483-1489, 1997[ISI][Medline].

48.   Wei, CM, Aarhus LL, Miller VM, and Burnett JC, Jr. Action of C-type natriuretic peptide in isolated canine arteries and veins. Am J Physiol Heart Circ Physiol 264: H71-H73, 1993[Abstract/Free Full Text].

49.   Wei, CM, Kim CH, Miller VM, and Burnett JC. Vasonatrin peptide: a unique synthetic natriuretic and vasorelaxing peptide. J Clin Invest 92: 2048-2052, 1993.

50.   Wennberg, PW, Miller VM, Rabelink T, and Burnett JC, Jr. Further attenuation of endothelium-dependent relaxation imparted by natriuretic peptide receptor antagonism. Am J Physiol Heart Circ Physiol 277: H1618-H1621, 1999[Abstract/Free Full Text].

51.   Winquist, RJ, Faison EP, Waldman SA, Schwartz K, Murad F, and Rapoport RM. Atrial natriuretic factor elicits an endothelium-independent relaxation and activates particulate guanylate cyclase in vascular smooth muscle. Proc Natl Acad Sci USA 81: 7661-7664, 1984[Abstract/Free Full Text].

52.   Yoshimura, K, Tod ML, Pier KG, and Rubin LJ. Role of venoconstriction in thromboxane-induced pulmonary hypertension and edema in lambs. J Appl Physiol 66: 929-935, 1989[Abstract/Free Full Text].

53.   Zhang, Z, Xiao Z, and Diamond SL. Shear stress induction of C-type natriuretic peptide (CNP) in endothelial cells is independent of NO autocrine signaling. Ann Biomed Eng 27: 419-426, 1999[ISI][Medline].

Am J Physiol Heart Circ Physiol 282(1):H273-H280
0363-6135/02 $5.00 Copyright © 2002 the American Physiological Society


This article has been cited by other articles:


Home page
 Am. J. Physiol. Lung Cell. Mol. Physiol.Home page
A.-C. Peyter, V. Muehlethaler, L. Liaudet, M. Marino, S. Di Bernardo, G. Diaceri, and J.-F. Tolsa
Muscarinic receptor M1 and phosphodiesterase 1 are key determinants in pulmonary vascular dysfunction following perinatal hypoxia in mice
Am J Physiol Lung Cell Mol Physiol, July 1, 2008; 295(1): L201 - L213.
[Abstract] [Full Text] [PDF]

Home page
 Am. J. Physiol. Lung Cell. Mol. Physiol.Home page
M. Marino, J. L. Beny, A. C. Peyter, R. Bychkov, G. Diaceri, and J. F. Tolsa
Perinatal hypoxia triggers alterations in K+ channels of adult pulmonary artery smooth muscle cells
Am J Physiol Lung Cell Mol Physiol, November 1, 2007; 293(5): L1171 - L1182.
[Abstract] [Full Text] [PDF]

Home page
 Am. J. Physiol. Lung Cell. Mol. Physiol.Home page
M. Taniguchi, Y. L. Kwak, K. A. Jones, D. O. Warner, and W. J. Perkins
Nitric oxide sensitivity in pulmonary artery and airway smooth muscle: a possible role for cGMP responsiveness
Am J Physiol Lung Cell Mol Physiol, May 1, 2006; 290(5): L1018 - L1027.
[Abstract] [Full Text] [PDF]

Home page
 Am. J. Physiol. Lung Cell. Mol. Physiol.Home page
Y. Gao and J. U. Raj
Role of veins in regulation of pulmonary circulation
Am J Physiol Lung Cell Mol Physiol, February 1, 2005; 288(2): L213 - L226.
[Abstract] [Full Text] [PDF]

Home page
 Am. J. Physiol. Lung Cell. Mol. Physiol.Home page
Y. Gao, S. Dhanakoti, E. M. Trevino, F. C. Sander, A. M. Portugal, and J. U. Raj
Effect of oxygen on cyclic GMP-dependent protein kinase-mediated relaxation in ovine fetal pulmonary arteries and veins
Am J Physiol Lung Cell Mol Physiol, September 1, 2003; 285(3): L611 - L618.
[Abstract] [Full Text] [PDF]

This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
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 ISI 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 ISI Web of Science (14)