Am J Physiol Heart Circ Physiol 286: H1889-H1894, 2004;
doi:10.1152/ajpheart.00863.2003
0363-6135/04 $5.00
A new method to denude the endothelium without damage to media: structural, functional, and biomechanical validation
Xiao Lu,
Xiaomei Guo,
Carlos Linares, and
Ghassan S. Kassab
Department of Biomedical Engineering, University of California, Irvine, California 92697
Submitted 10 September 2003
; accepted in final form 5 January 2004
 |
ABSTRACT
|
|---|
The intimial thickening that occurs in human and animal atherogenesis can be induced by mechanical injury to the endothelium. The objective of the present study was to develop a new method to induce arterial endothelial injury without damage to the media for future investigations of mechanisms of intimal thickening and atherogenesis. A specifically designed catheter was inserted into the common femoral artery of Wistar rats (n = 9) through an arteriotomic mouth. After application of Tyrode solution containing 0.14 M KCl on the surface of the vessel, the vessel contracted onto the catheter. The catheter was then moved back and forth to scrape away the endothelium. The left common femoral artery of the same rat was subjected to the standard balloon injury model. The two models were evaluated structurally, functionally, and biomechanically. Structurally, we verified that both techniques remove the endothelium, but the balloon method damages the media. Functionally, we examined the contractile response of the artery to [K+] and norepinephrine 2 days after the denudation. We found that the right femoral artery underwent contraction in response to [K+], whereas the left artery did not. Furthermore, neither artery responded to norepinephrine. Biomechanically, we measured the pressure-diameter relationship and the zero-stress state of the vessel and computed the stress-strain relation. The circumferential stretch ratios at 120 mmHg were 1.38 ± 0.08 for the control, 1.41 ± 0.08 (P > 0.05) for the new method, and 1.56 ± 0.09 for the balloon injury (P < 0.05). The opening angles at the zero-stress state were 113 ± 21° for the control, 102 ± 18° for the new method (P > 0.05), and 8 ± 13° for the balloon injury (P < 0.001). In conclusion, the new method removes the endothelium while maintaining the structure, contractile function, and biomechanical properties of the vessel.
injury; zero-stress state; balloon injury; endothelin
THE ENDOTHELIAL CELLS that line the lumen of the blood vessel are extremely important for the normal function of the vessel. The endothelium is the largest autocrine, paracrine, and endocrine organ that regulates vessel tone, monocyte adhesion, platelet activation, thrombogenesis, inflammation, lipid metabolism, vessel growth, and remodeling (21, 23). Because endothelial injury is an important risk factor for atherosclerosis, numerous models of endothelial injury have appeared in the literature (10, 12, 13). Previous investigations have induced endothelial injury mechanically (via balloon distension, micro-surgical instrument, or air desiccation) or chemically (via hydrochloric acid or Triton X-100) (2, 12). The most widely used model, however, is injury induced by a balloon overinflated into the lumen of the vessel and dragged along the lumen to scrape off the endothelium. Unfortunately, this technique not only damages the endothelium but also the media including the smooth muscle cells and elastin fibers (9, 12, 13). Many of the previous studies using balloon injury purposely intended to model angioplasty. Thus the combined effect of endothelial injury and overstretch of the vessel was intentional. The goal of the present study, however, was to separate the two effects, i.e., to develop a new endothelial injury model that does not damage the media.
We hypothesize that the approach proposed in this study will allow removal of the endothelium without injury to the media. We examined this hypothesis structurally by studying histological sections under light and scanning electron microscopy; functionally by inducing acute contraction with [K+], endothelin, and norepinephrine; and biomechanically by studying the zero-stress state and the stress-strain relationship. The present model will be useful for future studies on endothelial regeneration, atherogenesis, and remodeling.
|
MATERIALS AND METHODS
|
|---|
Animal preparation. All animal experiments were performed in accordance with national and local ethical guidelines, including the Institute of Laboratory Animal Research Guide, Public Health Service policy, Animal Welfare Act, and University of California-Irvine policies regarding the use of animals in research. Two groups of Wistar rats weighing 250–310 g were used in the present study. Group I was used to induce endothelial injury by the new endothelial injury method in the right common femoral artery and the standard balloon injury model in the left common femoral artery (11, 12, 15, 18). Group II was used as the sham control for the two vessels. A total of 18 rats was used for the two groups (9 rats in each).
The animals were anesthetized with pentobarbital sodium (60 mg/kg ip). Surgical anesthesia was maintained with pentobarbital sodium (20 mg·kg–1·h–1 ip). Arterial pressure was measured through a cannulated carotid artery. A jugular vein was cannulated for the administration of heparin (100 U/kg) for anticoagulation. A heating pad was used to maintain the body temperature of the animal. An incision was made on the skin, and the fat was resected away from the femoral artery. After exposure, the common femoral arteries in both legs were isolated along their entire lengths. The proximal femoral arteries were closed with arterial clamps. An arteriotomy was made on the distal femoral arteries where the arteriotomy area was in the near proximity of the bifurcation of superfacial femoral artery to obtain a sufficient specimen for the mechanical experiment. Figure 1 shows a schematic of a specifically designed catheter (outer diameter: 0.4 mm) with a stainless steel tube (diameter: 0.4 mm, length: 1 mm) fixed on a nylon suture that passes through the catheter (top). The catheter was inserted into the right femoral artery through the arteriotomic mouth (Fig. 1, bottom). Tyrode solution containing 0.14 M KCl was dripped on the external surface of the artery to induce contraction onto the catheter. The diameter of the catheter was 
90% of the vessel lumen diameter, which was chosen so that during the contraction the endothelial surface comes in contact with the catheter. The stainless steel tube was moved back and forth, three times, along the length of the artery. The arterial lumen was washed with saline containing heparin (50 U/ml) after removal of the tube. In the same animal, a 2-F Fogart balloon was inserted into the left common femoral artery. The balloon was pressurized to 1.05 atm and then moved back and forth, three times, along the lumen of the artery. The balloon pressure was subsequently removed, and the arterial lumen was washed with saline containing heparin (50 U/ml). The arteriotomy of both femoral arteries was sutured using 10-0 nylon monofilament sutures. The arterial clamp on each proximal artery was removed to restore blood flow. The skin on both incisions was closed, and the animal was allowed to recover. Water and food were replenished as needed. The sham-operated animals were treated identically including the creation of arteriotomy but no insertion of catheter.
Functional assessment. After 2 days, the incisions were reopened, and the femoral arteries were exposed. Tyrode solution containing 0.14 M KCl (endothelial independent) was dripped onto the outer surface of the arterial wall to elicit contraction (4). The arterial diameter was recorded during contraction. This procedure was repeated three times to obtain stable measurements. The KCl was washed away with saline for five times at the end of each contractile stimulation. This procedure was repeated with Tyrode solution containing KCl (0.14 M) and endothelin (20 pM). The vessel was again washed several times with saline. The vessel was then cannulated, and 1 ml of norepinephrine (2 µM) was administered intraluminally. The resulting diameter changes were recorded via video camera and subsquently measured with image-analysis software (SigmaScan Pro.5).
Pressure-diameter relationship. At the conclusion of the contractile experiments, the artery was cannulated from the angiotomic mouth and ligated proximally. Pressure-diameter measurements were made at a series of pressures (e.g., from 30 to 150 mmHg in increments of 30 mmHg). The outer diameter was videotaped at each corresponding pressure. The outer diameter measurements were made with image analysis software (SigmaScan Pro.5).
Determination of zero-stress state. Evans blue was injected into the jugular vein to stain the endothelium-denudated region for 1 h (14). The animal was then killed with an overdose of anesthesia. The femoral arteries in both legs were excised, and the arterial axial lengths both in vivo and in vitro were recorded to compute the longitudinal stretch ratio. Four rings were cut from the arterial segment to obtain the dimension of the artery at the no-load and zero-stress states, including inner and outer circumferences and wall area.
Structural examination. At the conclusion of the mechanical experiments, the arterial segments were fixed in buffered formalin and processed for histological examination under light microscopy. Additional arterial segments were examined by scanning electron microscopy. Those segments were cut axially, pinned flat on piece of cork, and fixed in 6.25% buffered glutaraldehyde overnight. The specimens were subsequently fixed in 1% OsO4 for 1 h. After being washed in double distilled water twice, the tissues were dehydrated in increasing concentrations of ethyl alcohol and subsequently in increasing concentration of hexamethyldisilazane. Dried tissue was mounted on an aluminum stage covered with quick-drying colloidal silver paste. The stage was coated with gold-palladium in a sputter coater, and the tissue was viewed with scanning electron microscopy.
Biomechanical analysis. The incompressibility condition was used to compute the inner radius (ri) as follows
 | (1) |
where ro is the outer radius at the loaded state and Ao is the wall area in the no-load state, respectively. The axial stretch ratio is 
z = l/lo, where l and lo are the vessel lengths in the loaded and no-load states, respectively.
The in vivo circumferential strain was computed according to the Green strain (
), which is defined as follows
 | (2) |
where 
i,o is the inner or outer circumferential stretch ratio (
); ci,o is the inner or outer circumference of the vessel in the loaded or no-load state, and 
is the inner or outer circumference in the zero-stress state. Similarly, the midwall strain was computed in reference to the midwall circumferences in the loaded or no-load state in reference to the zero-stress state. In the no-load state, the strain is referred to as the residual strain.
At equilibrium, the average circumferential Kirchhoff stress for a cylindrical vessel wall (
) is given by
 | (3) |
where P is the luminal pressure and h is the wall thickness of the vessel, respectively. Hence, the pressure-diameter relationship can be transformed into a mean stress-midwall strain relation as given by Eqs. 2 and 3.
Equation 2 can also be used to determine the inner and outer strains of the vessel wall from the respective circumferences. According to the Bernoulli-Kirchhoff hypothesis that plane sections remain plane during the deformation (inflation), the strain distribution from the inner to the outer wall must be linear (7). Hence, from the known values of strains at the inner and outer walls, we may obtain the strains in the interior of the vessel wall by linear interpolation.
The determination of transmural stress is much more difficult as there is no direct way to measure stress. A constitutive equation (stress-strain relation) is necessary to compute stress from the measured values of strain. In inflation experiments, there is deformation in the circumferential and longitudinal direction. Hence, the constitutive relation should relate the circumferential and longitudinal stresses to strains. If we assume that the longitudinal deformation is negligible and the vessel wall is homogeneous, we can approximate the transmural distribution of circumferential stress from the measured circumferential stress-strain relation.
Data analysis. Data are presented as arithmetic means ± SD unless otherwise stated. Significant differences between various parameters were determined with the use of parametric ANOVA, followed by Student's t-test. A probability of P < 0.05 was considered to be of a statistically significant difference.
|
RESULTS
|
|---|
The uptake of Evans blue and silver nitrate was indicative of the endothelium injury induced by both the new method and balloon injury. The photographs from the scanning electron microscope also attest to the denudation of endothelium, as shown in Fig. 2. In both models, the endothelium was absent and the luminal surface was covered by adherent platelets and granulocytes. Furthermore, the histological sections of media reveal significant structural damage with balloon distension, e.g., the internal elastic lamina is torn, but not with the new method, as seen in Fig. 3.
View larger version (128K):
[in this window]
[in a new window]
|
Fig. 3. Photographs from light microscopy. A: new method injury; B: balloon method injury. IEL, internal elastic lamina.
|
|
The removal of endothelium was also verified with the use of norepinephrine (endothelium dependent) 2 days after the injury. Similarly, the function of the media was assessed by the contraction of the blood vessel with KCl (endothelium independent) 2 days after the injury. The degree of contraction was quantified by the ratio of diameter of the vessel relative to the homeostatic diameter. Figure 4 shows that the vessel treated with the new method or by balloon injury did not contract with norepinephrine. Figure 5A shows that the femoral artery whose endothelium was denuded by the new method can still contract with K+ (endothelium independent), whereas the balloon injury vessel cannot. The degree of contraction in the new model, however, was smaller than that of control vessels (50%). The addition of endothelin to KCl induces additional contraction of the vessels treated with the new method, as shown in Fig. 5B. The measurements shown in Fig. 5B were made 10 min after application of the vasoactive substance. We found no statistically significant difference in the degree of contraction between KCl applied to a control vessel and a combination of KCl and endothelin applied to a vessel treated with the new method. This is in contrast to the balloon injury model, which did not contract at all.
View larger version (18K):
[in this window]
[in a new window]
|
Fig. 4. Norepinephrine (2 µM) induced arterial contraction of control vessels and those treated with the new method and balloon injury. The degree of contraction was quantified by the ratio of the diameter of the vessel (D) relative to the homeostatic diameter (Dh).
|
|
View larger version (23K):
[in this window]
[in a new window]
|
Fig. 5. A: KCl (0.14 M) induced arterial contraction of control vessels. B: measurements of arterial diameter after 10 min with the addition of endothelin. *Statistical significance (P < 0.05).
|
|
The pressure-diameter relationship is shown in Fig. 6A for the control vessels as well as for denudated vessels with the balloon injury and new method. The pressure-diameter data are transformed into mean stress-midwall strain relationship as shown in Fig. 6B. The stress and strain were computed with reference to the zero-stress state. The zero-stress state is characterized by the opening angle, which is defined as the angle subtended by two radii connecting the midpoint of the inner wall. The data on the opening angles are shown in Fig. 7A. There was no statistically significant difference between the opening angle in the control vessels and those treated with the new method. There was a large and significant decrease, however, in the vessels treated with the balloon method. The changes in the residual strain shown in Fig. 7B were consistent with the observed changes in opening angle. Both inner and outer residual strains were significantly reduced after the balloon injury. The balloon method, however, altered the transmural distribution of strain and stress, as shown in Fig. 8. The transmural strain distribution is shown in Fig. 8A, where the inner and outer strains are linearly interpolated across the vessel wall as described in MATERIALS AND METHODS. The corresponding stress distribution shown in Fig. 8B was obtained from the stress-strain relation shown in Fig. 6B for the inner and outer strains and their interpolated values. The ratios of inner to outer strain were 1.4 ± 0.27 for control, 1.4 ± 0.25 (P > 0.05) for the new method, and 2.4 ± 0.55 (P < 0.01) for balloon injury. Similarly, the ratios of inner to outer stress were 2.2 ± 0.41 for control, 3.6 ± 0.69 (P = 0.06) for the new method, and 12.0 ± 2.9 (P < 0.001) for balloon injury. The foregoing results on stress and strain were calculated at physiological pressures (120 mmHg) in reference to the zero-stress state.
View larger version (22K):
[in this window]
[in a new window]
|
Fig. 6. A: in situ pressure-diameter relationship; B: stress-strain relationship. *Statistical significance (P < 0.05).
|
|
View larger version (28K):
[in this window]
[in a new window]
|
Fig. 7. A: opening angle; B: residual strains at the inner and outer wall, respectively. *Statistical significance (P < 0.05).
|
|
View larger version (17K):
[in this window]
[in a new window]
|
Fig. 8. Transmural circumferential stress and strain at the inner (Ri) and outer wall (Ro) at physiological pressure (120 mmHg). Interpolated values of strain are given through the wall at 25%, 50%, and 75% of the wall thickness. The corresponding values of stress are computed from the stress-strain relationship shown in Fig. 5. *Statistical significance (P < 0.05).
|
|
|
DISCUSSION
|
|---|
A new model of endothelial injury. Several methods have been used to induce endothelial injury that either involve a mechanical or chemical insult. These methods, however, have some shortcomings. For example, the use of air bubbles does not ensure that the endothelium of the entire region of interest is removed or that the result is reproducible (4, 17). With the use of chemicals, on the other hand, it is difficult to limit the injury to the endothelial surface and the degree of injury is critically dependent on the duration of chemical treatment (2, 12). In the present study, we developed a method that is local, well defined, and reproducible. Furthermore, the scraping of endothelium is done when the media is contracted to protect it from injury. Finally, we provide structural, functional, and biomechanical measurements to validate the model as outlined below.
Structural validation. We confirmed that the damage to the endothelium by the new method was complete and reproducible by the extensive uptake of Evans blue and silver nitrate throughout the region of interest. The scanning electron microscopy photomicrographs also confirmed the denudation of the endothelium, as shown in Fig. 2. The media, on the other hand, showed normal structure under light microscopy, as seen in Fig. 3. The balloon injury method was equally successful in denudation but caused significant damage to the media and in particular to the internal elastic lamina (5, 6, 16, 19, 22, 24, 25). Finally, the denudation was confirmed by the lack of contraction in the presence of norepinephrine (Fig. 4).
Functional validation. The functional studies, quantified by the contraction of the media, confirmed that the vessel treated with the new method will contract to 50% of the control value 2 days after the insult (Fig. 5). This can be compared with the zero contraction for the balloon injury model. Similarly, it was found that vessels denudated with Triton can only contract to 50% of the control values 2 days after treatment (12). These investigators also verified that the media was not damaged structurally during Triton treatment. Hence, this poses the question of why an apparently normal media only contracts to 50% of control in the absence of endothelial cells.
It is well known that the endothelium plays an important role in the control of smooth muscle tone by production and release of various vasoactive substances, e.g., most notably nitric oxide and endothelin (3, 20). Hence, even normal media may not have the same vasoactive ability in the absence of endothelium. To test this hypothesis, we added an in vivo concentration of endothelin in addition to [K+] and found that the vessel increased the degree of contraction to those of control values. Hence, the role of endothelium (e.g., the release of endothelin) is essential for the normal contraction of the media.
Biomechanical validation. We verified that the circumferential mechanical properties of the vessel, expressed in terms of pressure-diameter and stress-strain relationships, are unaltered after removal of endothelium with the new method (Fig. 6). This is an expected finding because the endothelium is relatively thin in the normal artery and does not contribute significantly to the circumferential mechanical properties. The balloon model, however, overdistends the vessel and increases the diameter at any given pressure or the strain at any given stress.
We also measured the changes in the opening angle and consequently the residual strain. We found that the new method preserves the control values of opening angle and residual strain, whereas the balloon method significantly lowers both (Fig. 7). It has previously been shown that the residual strain significantly reduces the stress concentration at the inner portion of the vessel wall at the in vivo state and leads to a uniformity of transmural strain (1, 8). These features are preserved using the new method but are significantly altered with the balloon model. The balloon injury model imposes stress and strain concentration at the intima, as shown in Fig. 8, which is likely responsible for some of the remodeling observed in this model (10).
Significance of study. Arterial injury is known to initiate repair and remodeling processes that are implicated in the pathogenesis of important vascular disorders including atherogenesis and restenosis. The remodeling processes of structure and function are very likely to be injury specific. Hence, it is essential to develop models where the degree of injury is both well defined and reproducible. In the present study, we developed such a method for pure endothelial injury. In future studies, this model will be used to understand endothelial regeneration, vascular remodeling, and atherogenesis.
|
ACKNOWLEDGMENTS
|
|---|
GRANTS
This research was supported in part by National Heart, Lung, and Blood Institute Grant 2 R01 HL-055554-06 and American Heart Association (AHA) Grant 0140036N. G. S. Kassab was the recipient of an AHA Established Investigator Award.
|
FOOTNOTES
|
|---|
Address for reprint requests and other correspondence: G. S. Kassab, Dept. of Biomedical Engineering, Univ. of California, 204 Rockwell Engineering Center, Irvine, CA 92697-2715 (E-mail: gkassab{at}uci.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
|
|---|
- Chuong CJ and Fung YC. On residual stresses in arteries. J Biomech Eng 108: 189–192, 1986.[ISI][Medline]
- Clowes AW, Reidy MA, and Clowes M. Kinetics of cellular proliferation after injury: 1. Smooth muscle cell growth in the absence of endothelium. Lab Invest 49: 327–333, 1983.[ISI][Medline]
- Cooper CJ, Landzberg MJ, Anderson TJ, Charbonneau F, Creager MA, Ganz P, and Selwyn AP. Role of nitric oxide in the local regulation of pulmonary vascular resistance in humans. Circulation 93: 266–271, 1996.[Abstract/Free Full Text]
- Emerson GG and Segal SS. Endothelial cell pathway for conduction of hyperpolarization and vasodilation along hamster feed artery. Circ Res 86: 94–100, 2000.[Abstract/Free Full Text]
- Fonseca FA, Izar MC, Fuster V, Gallo R, Padurean A, Fallon JT, Schachter EN, Chesebro JH, and Badimon JJ. Chronic endothelial dysfunction after oversized coronary balloon angioplasty in pigs: a 12-week follow-up of coronary vasoreactivity in vivo and in vitro. Atherosclerosis 154: 61–69, 2001.[CrossRef][ISI][Medline]
- Fujikawa K, Presman E, Isner JM, and Varticovski L. Expression of tie1 and tie2 proteins during reendothelialization in balloon-injured rat carotid artery. J Vasc Res 36: 272–281, 1999.[CrossRef][ISI][Medline]
- Fung YC. Foundations of Solid Mechanics. Englewood Cliffs, NJ: Prentice-Hall, 1965.
- Fung YC and Liu SQ. Strain distribution in small blood vessels with zero-stress state taken into consideration. Am J Physiol Heart Circ Physiol 262: H544–H552, 1992.[Abstract/Free Full Text]
- Gerritsen ME and Bloor CM. Endothelial cell gene expression in response to injury. FASEB J 7: 523–532, 1993.[Abstract]
- Gertz SD, Gimple LW, Banai S, Ragosta M, Powers ER, Roberts WC, Perez LS, and Sarembock IJ. Geometric remodeling is not the principal pathogenetic process in restenosis after balloon angioplasty. Evidence from correlative angiographic-histomorphometric studies of atherosclerotic arteries in rabbits. Circulation 90: 3001–3008, 1994.[Abstract/Free Full Text]
- Hayashi S, Watanabe N, Nakazawa K, Suzuki J, Tsushima K, Tamatani T, Sakamoto S, and Isobe M. Roles of P-selectin in inflammation, neointimal formation, and vascular remodeling in balloon-injured rat carotid arteries. Circulation 102: 17101–17107, 2000.
- Jamal A, Bendeck M, and Langille BL. Structural changes and recovery of function after arterial injury. Arterioscler Thromb 12: 307–317, 1992.[Abstract/Free Full Text]
- Kadar A and Bjorkerud S. Arterial remodeling following mechanical injury. The role and nature of smooth muscle cells. Pathol Res Pract 180: 342–347, 1985.[ISI][Medline]
- Langille BL and O'Donnell F. Reductions in arterial diameter produced by chronic decrease in blood flow are endothelium-dependent. Science 231: 405–407, 1986.[Abstract/Free Full Text]
- Lemay J, Hou Y, and deBlois D. Evidence that nitric oxide regulates AT1-receptor agonist and antagonist efficacy in rat injured carotid artery. J Cardiovasc Pharmacol 35: 693–699, 2000.[CrossRef][ISI][Medline]
- Mc Fadden EP, Bauters C, Lablanche JM, Quandalle P, Leroy F, and Bertrand ME. Response of human coronary arteries to serotonin after injury by coronary angioplasty. Circulation 88: 2076–2085, 1993.[Abstract/Free Full Text]
- Nossum V, Koteng S, and Brubakk AO. Endothelial damage by bubbles in the pulmonary artery of the pig. Undersea Hyperb Med 26: 1–8, 1999.[ISI][Medline]
- Nunes GL, Sgoutas DS, Redden RA, Sigman SR, Gravanis MB, King SB, and Berk BC. Combination of vitamins C and E alters the response to coronary balloon injury in the pig. Arterioscler Thromb Vasc Biol 15: 156–165, 1995.[Abstract/Free Full Text]
- Picard P, Smith PJ, Monge JC, and Stewart DJ. Expression of endothelial factors after arterial injury in the rat. J Cardiovasc Pharmacol 31, Suppl 1: S323–S327, 1998.[CrossRef][ISI][Medline]
- Schiffrin EL. Endothelin: role in hypertension. Biol Res 31: 199–208, 1998.[ISI][Medline]
- Schwartz SM, deBlois D, and O'Brien ERM. The intima: soil for atherosclerosis and restenosis. Circ Res 77: 445–465, 1995.[Free Full Text]
- Tulis DA, Durante W, Peyton KJ, Evans AJ, and Schafer AI. Heme oxygenase-1 attenuates vascular remodeling following balloon injury in rat carotid arteries. Atherosclerosis 155: 113–122, 2001.[CrossRef][ISI][Medline]
- Vogel RA. Cholesterol lowering and endothelial function. Am J Med 107: 479–487, 1999.[CrossRef][ISI][Medline]
- Ward MR, Tsao PS, Agrotis A, Dilley RJ, Jennings GL, and Bobik A. Low blood flow after angioplasty augments mechanism of restenosis: inward vessel remodeling, cell migration, and activity of genes regulating migration. Arterioscler Thromb Vasc Biol 21: 208–213, 2001.[Abstract/Free Full Text]
- Wright MB, Seifert RA, and Bowen-Pope DF. Protein-tyrosine phosphatases in the vessel wall: differential expression after acute arterial injury. Arterioscler Thromb Vasc Biol 20: 1189–1198, 2000.[Abstract/Free Full Text]
Copyright © 2004 by the American Physiological Society.
TOP
ABSTRACT
MATERIALS AND METHODS
