Keratin expression in cutaneous lichen planus

The characteristic expression of keratins by keratinocytes is well documented. A typical 'hyperproliferative' profile of epidermal keratin expression occurs in psoriasis, wound healing and warts. This study analyses keratin expression in cutaneous lichen planus to determine abnormalities of differentiation occurring in this inflammatory disorder. Using a panel of monoclonal antibodies 28 samples (20 patients) were studied. The results showed that squamous differentiation was unaffected, with keratins K1 and K10 being expressed normally for the site sampled. The main abnormalities included extension of reactivity of the basal cell marker, LH8, into the suprabasal compartment. Keratin K17, usually restricted to adnexal structures, was variably expressed in the basal and suprabasal layers of the interfollicular epithelium of affected epidermis. Keratins K6 and K16, found suprabasally in hyperproliferative states, were detected both basally and suprabasally in all diseased samples. The keratin profile in lichen planus is analogous to the wound healing response. Suprabasal keratin K17 is found in psoriasis, wound healing and viral warts so the changes in keratin K17 may reflect hyperproliferative changes. It is likely that the changes in epidermal keratin expression are due to up-regulation of specific keratin genes by the production of cytokines and inflammatory mediators from the lymphocytic infiltrate typical of lichen planus.

Ramipril and experimental vein graft intimal hyperplasia

Angiotensin-converting enzyme (ACE) inhibitors have been shown to reduce the intimal proliferation in animal models of arterial angioplasty and vein bypass grafting. This study examines the effect of high-dose ramipril, an ACE inhibitor that does not contain a sulfhydryl group, on the development of intimal hyperplasia in experimental vein bypass grafts. Twenty New Zealand White rabbits underwent common carotid interposition bypass grafting. Twelve were treated with ramipril (2 mg/kg/day; po) five days prior to surgery and thereafter until harvest. The remaining 8 animals were used as controls. Vein grafts were harvested at twenty-eight days by pressure fixation (80 mmHg). The grafts were sectioned into proximal, middle, and distal thirds, and the thickness of the intima and the media and the area of the lumen from each segment were determined by videomorphometry. The effect of ramipril on the [H3]thymidine incorporation into DNA of serum-stimulated smooth muscle cells (culture passage 6 to 12) was also assessed. There was a 50% mortality rate in the rabbits that received ramipril, and this was assumed to be related to the high dose of the drug. Ramipril treatment reduced mean vein graft intimal area by 34% (P > 0.05), but this was accompanied by an increase of 73% in the mean medial area of the vein grafts as compared with controls. These changes resulted in a decrease in the mean intimal ratio (intima/[intima + media]) by 39% in the ramipril group as compared with controls. Ramipril did not inhibit [H3]thymidine incorporation into DNA of serum-stimulated smooth muscle cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Prolonged hypercholesterolemia induces reversible alterations in venous vasomotor function

Hypercholesterolemia is associated with altered arterial endothelial and smooth muscle cell function. This study examines the influence of hypercholesterolemia on external jugular venous endothelial and smooth muscle cell vasoreactivity. Eighteen New Zealand White rabbits received a 1% cholesterol diet: in nine animals, this diet was continued until harvest at 8 weeks (hypercholesterolemic group), but in the other nine animals, the diet was changed to standard rabbit chow after 4 weeks and continued for a further 4 weeks (cholesterol reduction group). The change in the diet resulted in a 70% decrease in serum cholesterol concentration. Eight animals received standard rabbit chow for 8 weeks. Hypercholesterolemia induced hypersensitivity and increased maximal contractions to norepinephrine and endothelin-1. In addition, the maximal response to bradykinin increased, and a contraction to serotonin was induced in the veins from the hypercholesterolemic animals. Cholesterol reduction induced bradykinin hypersensitivity but had no effect on endothelin-1 sensitivity. Norepinephrine hypersensitivity returned to normal and the serotonin response disappeared. A decrease in the maximal contractile responses to these agonists was also observed. Hypercholesterolemia interfered with dose-dependent, EDRF (endothelium derived relaxing factor)-mediated relaxation induced by acetylcholine but, following the reduction of serum cholesterol, normal acetylcholine-induced, endothelium-dependent relaxation returned. Non-endothelium-dependent relaxation to sodium nitroprusside of precontracted veins was unaffected by the presence of high cholesterol concentrations. There were no morphological changes apparent in the veins of either the hypercholesterolemic or the cholesterol reduction groups. In conclusion, this study suggests that hypercholesterolemia induces reversible functional abnormalities in venous tissue and this ability of the jugular veins to recover may be, in part, linked to the lack of morphological changes.

Pathophysiology of vein graft failure: a review

Vein bypass grafting is an integral component of cardiovascular surgical practice for both arterial and venous diseases. However, many of these grafts will eventually fail due to either intrinsic or extrinsic causes. This review examines the current understanding and knowledge of venous histology, vein graft pathology and the associated endothelial and smooth muscle cell physiology and pharmacology. In addition, the status of research on the therapeutic control of vein graft intimal hyperplasia and accelerated atherosclerosis is assessed.

Lack of effect of carbon monoxide inhibitor on relaxation induced by electrical field stimulation in corpus cavernosum

Carbon monoxide has been proposed as a possible neurotransmitter because of its ability to bind to the iron atom of the heme of guanylyl cyclase, which is similar to that of nitric oxide. To determine whether carbon monoxide exerts an effect on the penis, strips of rabbit corpus cavernosum were mounted in an organ bath for isometric tension studies and the effect of zinc deuteroporphyrin, an inhibitor of heme oxygenase which metabolizes hemoprotein and releases carbon monoxide, on relaxation induced by electrical field stimulation (neurally mediated) was determined. Also observed was relaxation induced by electrical field stimulation after incubation with atropine and guanethidine to isolate nonadrenergic noncholinergic neurotransmission. Zinc deuteroporphyrin (10(-6) M, 10(-5) M, 10(-4) M and 3 x 10(-4) M) did not affect relaxation induced by electrical field stimulation in the absence or presence of guanethidine and atropine. Therefore, it appears that carbon monoxide does not contribute to neurally mediated relaxation of the rabbit corpus cavernosum.

Bradykinin receptor modulation in vein grafts

Following vein grafting, bradykinin B2 receptor-mediated responses in the vein graft are decreased and B1 receptor-mediated responses are increased. It is not known whether these changes in bradykinin receptor responses are due to nonspecific changes, local inflammation, or arterial hemodynamics. Four experimental tissue models were studied to discriminate among these possibilities. Twelve New Zealand White rabbits underwent excision of native vein (n = 4), external jugular veno-venous bypass (n = 4), or common carotid veno-arterial bypass (n = 4). Grafts and unoperated contralateral jugular veins (n = 4) were harvested at 28 days postoperatively. Isometric tension studies were performed on four rings from each vein and vein graft. The responses to bradykinin, a B2 agonist (BK: 10(-12) to 10(-5) M) and des-Arg9-bradykinin, a B1 agonist (DABK; 10(-12) to 10(-5) M) were recorded. Compared to native veins, the results show a progressive attenuation in BK sensitivity in contralateral veins, veno-venous grafts, and veno-arterial grafts, and the development of DABK sensitivity in the contralateral veins and both vein graft models. The alterations in B2 receptor-mediated responses appear therefore to be induced by a combination of the surgical procedure and arterialization, while changes in B1 receptor-mediated responses appear to be related solely to nonspecific sensitization of the cardiovascular tissue following the operative procedure. Thus, it appears from this study that there are two distinct mechanisms involved in the modulation of bradykinin receptors in vein grafts after implantation into the arterial circulation.

The expression and function of G-proteins in experimental intimal hyperplasia

G-proteins are membrane-bound signal transduction proteins which couple extracellular receptor signals to various effectors. This study examines the expression and the function of G-proteins (alpha i, alpha s, alpha q, and alpha o) in experimental intimal hyperplasia. Vein bypass grafts were placed in 30 New Zealand White rabbits and were harvested after 28 d. The contralateral jugular veins served as controls. Isometric tension studies were performed on rings from veins and vein grafts (n = 10), and Western blot and mRNA analyses were performed in another 20 vessels. There was a fivefold increase in alpha q, a 2.7-fold increase in the alpha i2, and a 3.3-fold increase in alpha s expressions in vein grafts compared with veins. Detectable expression of alpha i3 was observed in vein grafts but not in jugular veins. In addition, there was a 3.8-fold increase in beta subunits in the vein grafts compared with the veins. mRNA for alpha s, alpha i3, and alpha i2 were all elevated in the vein grafts. No detectable levels of the alpha i1 protein or its mRNA were present in either veins or vein grafts. Contractile responses in the veins were not inhibited by pertussis toxin. The contractile responses to norepinephrine were enhanced by twofold, and the responses to serotonin developed de novo in vein grafts compared with veins. The contractile responses to both norepinephrine and serotonin were only partially inhibited by pertussis toxin in the vein grafts even though there was 100% ADP ribosylation with pertussis toxin in both veins and vein grafts. These data suggest that intimal hyperplasia is associated with increased or novel expression of G-proteins in vivo which occur simultaneously with the development of pertussis toxin-sensitive contractile responses. Changes in G-proteins at a transcriptional level or at the level of RNA stability may be involved in the response of smooth muscle cells to injury and to intimal hyperplasia formation.

Pathobiology of intimal hyperplasia

In the current vascular interventional environment, high restenosis rates have increased awareness of the significance of intimal hyperplasia, a chronic structural lesion that develops after vessel wall injury, and which can lead to luminal stenosis and occlusion. Intimal hyperplasia may be defined as the abnormal migration and proliferation of vascular smooth muscle cells with associated deposition of extracellular connective tissue matrix. The pathology of intimal hyperplasia is reviewed with particular attention to its physiology, pharmacology, cell biology and molecular biology.

Postoperative reduction of high serum cholesterol concentrations and experimental vein bypass grafts. Effect on the development of intimal hyperplasia and abnormal vasomotor function

Hypercholesterolemia is an important contributor to the development of intimal hyperplasia and superimposed accelerated atherosclerosis in vein bypass grafts. This study examines the effect of dietary modification of serum cholesterol on the development of intimal hyperplasia and vasomotor function of vein grafts. Thirty male New Zealand White rabbits had a right carotid vein bypass graft and were put to death 28 days after the operation. Twenty animals received a 1% cholesterol diet for 4 weeks before the operation. In 10 animals this diet was continued until harvest (hypercholesterolemia group). In another 10 animals the diet was changed to standard rabbit chow on the day of the surgical procedure and continued until harvest (cholesterol reduction group). The last 10 animals were control subjects. Vein grafts were harvested either for histologic study or for in vitro isometric tension studies. Cumulative dose response curves to norepinephrine, serotonin, bradykinin, and endothelin-1 were determined. After in situ pressure fixation, intimal thicknesses of the vein grafts were measured by videomorphometry. The change in diet produced a 74% reduction in serum cholesterol concentration within 28 days. There was a 26% reduction in the intimal thickness of vein graft intimal hyperplasia and the macroscopic disappearance of atheromatous lesions from the graft wall, which are always observed in vein grafts from the hypercholesterolemia group. Cholesterol reduction did not change hypercholesterolemia-induced agonist supersensitivity. Therefore, cholesterol reduction slows the formation of intimal hyperplasia in vein grafts but does not prevent the persistence of the hypercholesterolemia-associated smooth muscle phenotype.

Experimental evidence for endothelium dependent relaxation and neuronal nitric oxide in corpus cavernosum

It is known that penile erection is mediated primarily through the release of a nonadrenergic noncholinergic (NANC) neurotransmitter which has been recently identified as nitric oxide (NO). To evaluate whether the endothelium is involved in neurally mediated relaxation in corpus cavernosum, we determined electrical field stimulation (EFS) induced relaxation in both the presence and absence of endothelium, and we tested the effect of an inhibitor of NO synthase, NG-nitro-L-arginine (NOARG), in the absence of endothelium to examine if de-endothelialized tissue can still generate NO. Isolated corpus cavernosal strips from New Zealand White rabbits were used for isometric tension study using organ chambers. The endothelium was removed through denuding tissue. After the tissue was contracted with norepinephrine, EFS was performed at frequencies of 5, 15 and 40 Hz in the presence of guanethidine and atropine to evaluate NANC-selective nerural relaxation. The relaxation induced by EFS was observed after preincubation with NOARG(10(-4) M) for 30 minutes. L-arginine (10(-3) M) was then added for 30 minutes in the presence of NOARG before a second set of EFS studies were performed. Following norepinephrine precontraction, EFS relaxed corporal strips in both the intact and de-endothelialized strips. However, deendothelialization significantly impaired EFS induced relaxation (p < 0.05). NOARG attenuated relaxation induced by EFS and the addition of L-arginine reversed the inhibitory effect of NOARG in the strips with endothelium. In the strips without endothelium, NOARG still inhibited EFS induced relaxation. This relaxation was reversed by the addition of L-arginine.(ABSTRACT TRUNCATED AT 250 WORDS)

Reduction of experimental vein graft intimal hyperplasia and preservation of nitric oxide-mediated relaxation by the nitric oxide precursor L-arginine

BACKGROUND

Previous studies in animals and human beings have shown that vein bypass grafts exhibit diminished endothelium-dependent relaxation and the development of intimal hyperplasia. This study examines the effect of L-arginine on experimental vein graft endothelial cell function and the development of intimal hyperplasia.

METHODS

Common carotid vein bypass grafts were performed in 24 New Zealand White rabbits: 12 were controls and 12 received L-arginine (2.25%) orally 7 days before operation and thereafter until harvest 28 days after operation. Intimal and medial dimensions were determined by planimetry on pressure-fixed vessels. Relaxation to acetylcholine, serotonin, calcium ionophore (A23187), and sodium nitroprusside was performed on precontracted vessel rings.

RESULTS

Arginine-treated vein grafts showed a 47% reduction in mean intimal thickness (p < 0.001) compared with controls. By scanning and transmission electron microscopy, all vein grafts showed a confluent endothelium. In contrast to control grafts, which do not relax to acetylcholine and serotonin, arginine-treated vein grafts relaxed in response to both agonists. There was a significant increase (p < 0.05) in the maximal relaxation to calcium ionophore (A23187) in arginine-treated vein grafts compared with control grafts. Non-endothelium-dependent responses to sodium nitroprusside were equivalent in all vein grafts.

CONCLUSIONS

This study shows that oral L-arginine supplementation significantly reduces intimal hyperplasia and preserves nitric oxide-mediated relaxation in experimental vein grafts, suggesting a role for nitric oxide in the regulation of the cellular events that lead to intimal hyperplasia.

Systemic hypertension and hypercholesterolemia in vein grafts: effects on the function and morphology of experimental vein grafts

Hypertension and hypercholesterolemia are known risk factors for the development of atherosclerosis and are considered to influence the development of vein graft intimal hyperplasia. This study examines the effect of hypertension (two-kidney, one-clip model for 8 weeks) and hypercholesterolemia (1% cholesterol diet for 8 weeks) individually and in combination on the formation of intimal hyperplasia and the vasomotor function of vein grafts. Forty New Zealand White rabbits underwent a carotid vein bypass graft. Ten were controls, 10 were hypertensive, 10 were hypercholesterolemic, and 10 had both hypertension and hypercholesterolemia. Hypertension and/or hypercholesterolemia were present for 4 weeks prior to and for 4 weeks after surgery. All vein grafts were harvested at 4 weeks postoperatively for histology (n = 6) or contractility studies (n = 4). Compared to controls, hypercholesterolemia increased intimal but not medial thicknesses of the vein grafts and enhanced smooth muscle cell contractility. Hypertension did not increase vein graft intimal or medial thicknesses but did augment vein graft contractility compared to controls. Hypertension with hypercholesterolemia increased intimal and medial thicknesses and enhanced vasoreactivity in vein grafts. The results show that hypertension influences the vasoreactivity but not the development of intimal hyperplasia in vein grafts. When hypertension is combined with hypercholesterolemia, there is both an increase in the medial thickness and an attenuation of vasomotor function compared to hypercholesterolemia alone, although there is no further increase in intimal hyperplasia formation. Therefore, this study suggests that the combination of both atherogenic risk factors does not act synergistically in promoting either the formation of intimal hyperplasia or vasomotor dysfunction in vein grafts.

Control of the structural and functional consequences of vein graft intimal hyperplasia with a 21-aminosteroid--U74389G

Following angioplasty and vein bypass grafting, there is endothelial cell injury, infiltration of leukocytes and smooth muscle cell (SMC) proliferation leading to intimal hyperplasia which may result in stenosis and can lead to eventual occlusion. This study examines the effect of the 21-aminosteroid U74389G (Upjohn Company), on the formation of vein graft intimal hyperplasia in vivo and on SMC DNA synthesis and proliferation in vitro. Twenty New Zealand White rabbits had a right carotid interposition bypass graft using the ipsilateral external jugular vein. Ten animals received chronic oral therapy with U74389G (25 mg/kg/day; begun 5 days before surgery and continued until harvest) and 10 control animals received vehicle only. All animals were sacrificed on the 28th postoperative day. Vein grafts were harvested either for histology/videomorphometry (n = 6 per group) or for in vitro isometric tension studies (n = 4; four 5 mm rings per graft). The incorporation of [3H]thymidine into the cellular DNA of serum-stimulated rabbit aortic SMC (passage 6th to 12th) was assessed in the presence of increasing concentrations of U74389G (10(-9) to 10(-4) M). The effect of U74389G on in vitro cell proliferation was also assessed. Treatment with U74389G produced a 44% decrease in overall mean intimal thickness from 82 +/- 1 microM (mean +/- S.E.M.) in the controls to 57 +/- 10 microM in the U74389G treated vein grafts (p = 0.003).(ABSTRACT TRUNCATED AT 250 WORDS)

The functional and morphological consequences of balloon catheter injury in veins

Endovascular procedures are now used to treat occlusive arterial and venous diseases. However, after arterial catheter injury, intimal hyperplasia develops and there is altered endothelial and smooth muscle cell vasoreactivity of the vessel segment. This study examines the morphology and vasoreactivity of veins which have undergone balloon catheter injury. Under direct vision, 22 jugular veins of 11 New Zealand White rabbits were catheterized with a Fogarty balloon catheter (4Fr, three passes, 0.75 ml H2O inflation). Ten uninstrumented jugular veins from 5 additional animals were used as controls. Immediately after balloon injury, 10 jugular veins were harvested. Scanning electron microscopy of these vessels confirmed complete endothelial denudation and no in vitro endothelium-dependent relaxation was observed. After 28 days, 12 veins were harvested. There were no occlusions. Histologically, the 28-day balloon-injured veins had an almost confluent endothelium. However, there was medial hypertrophy but no development of intimal hyperplasia. There were no significant changes in the contractile responses of the balloon-injured veins after 28 days to norepinephrine. Bradykinin and histamine responses were markedly attenuated. Following bradykinin precontraction, balloon-injured veins showed diminished acetylcholine sensitivity with a reduced maximal response, and a small decrease in serotonin sensitivity with a markedly decreased maximal response. In contrast, there was an increased sensitivity in response to sodium nitroprusside without a change in maximal response in precontracted balloon-injured veins. This study shows that after 28 days venous balloon injury does not induce the development of intimal hyperplasia but does reduce overall endothelial dependent relaxation (acetylcholine- and serotonin-mediated) with increased sensitivity to endothelial independent relaxation (sodium nitroprusside-mediated). These findings would suggest that when compared to arterial balloon injury, venous balloon injury does not carry the same histological and vasoconstrictive sequelae but does demonstrate similarly impaired endothelial cell function.

Diabetes mellitus and experimental vein graft structure and function

PURPOSE

Diabetes mellitus is a known risk factor for accelerated atherosclerosis and for postangioplasty restenosis.

METHODS

This study examines the effect of chronic, uncontrolled, alloxan-induced diabetes on the structure and vasomotor function of vein bypass grafts in 20 male New Zealand white rabbits with diabetes and in 10 controls. After 8 weeks of diabetes, a common carotid vein bypass graft was performed. Four weeks after operation, vein grafts and contralateral jugular veins were harvested.

RESULTS

Diabetes induced a twofold increase in the vein graft intimal thickness compared with control. There was no change in medial thickness. Electron microscopy of the vein grafts in diabetes revealed intercellular gaps in the endothelium lining and abnormal endothelial cell junctions compared with controls. Diabetes significantly increased the maximal contractions generated in vein grafts to all contractile agonists tested without any change in sensitivity.

CONCLUSIONS

This study demonstrates that diabetes alters endothelial cell structure and increases the development of intimal hyperplasia with increased maximal contractility in vein grafts and therefore suggests that the vein grafts in diabetes are more susceptible to early stenosis.

Long-term human vein graft contractility and morphology: a functional and histopathological study of retrieved coronary vein grafts

Vasoreactivity of 11 coronary artery vein bypass grafts and 13 human saphenous veins was examined. Isometric tension studies were performed in response to potassium chloride (110 mmol/l), noradrenaline (10(-9)-10(-4) mol/l), serotonin (10(-9)-10(-4) mol/l) and histamine (10(-8)-10(-2) mol/l). After precontraction with noradrenaline (10(-5) mol/l), the response to acetylcholine (10(-8)-10(-4) mol/l) and the calcium ionophore A23187 (10(-8)-10(-4) mol/l) was also assessed. Results are given as mean(s.e.m.). Compared with saphenous veins, vein grafts showed decreased sensitivity to noradrenaline (1.7(0.5) versus 0.4(0.1) mumol/l, P = 0.01), no change in sensitivity to serotonin (55(18) versus 37(15) mumol/l, P > 0.05) and supersensitivity to histamine (3.2(0.9) versus 30.1(13.2) mumol/l, P = 0.01). Vein grafts had a decreased maximal contraction to potassium chloride (1.1(0.3) versus 5.5(0.8) g, P = 0.0001), noradrenaline (1.2(0.3) versus 4.1(0.8) g, P = 0.005), histamine (1.2(0.3) versus 4.5(0.8) g, P = 0.003) and serotonin (0.7(0.2) versus 5.7(0.6) g, P = 0.0002) compared with saphenous vein. Precontracted vein grafts did not relax in response to acetylcholine; in contrast, saphenous vein relaxed in a dose-dependent manner to a maximal relaxation of 22(3) per cent. Both saphenous vein and vein graft relaxed in response to A23187. Vein graft intimal thickness was approximately fourfold greater than that of saphenous vein (540(110) versus 136(30) microns). Scanning electron microscopy of vein and vein graft revealed an intact endothelium. Coronary artery vein grafts are capable of responding to various contractile agonists; these response are notably different from those of saphenous vein and there is a loss of endothelium-dependent relaxation. Even at a late stage vein grafts are not inert but are functional conduits with an abnormally responsive endothelium and a less potent, but significantly altered, smooth muscle contractile profile.

Increased concentrations of angiotensin-converting enzyme in the intimal hyperplasia of experimental vein grafts

Local renin and angiotensin-converting enzyme (ACE) activity were recently implicated in development of intimal hyperplasia after vascular injury, but little is known about the local responses of angiotensin I/II (AI/AII) and local ACE activity in vein graft physiology. The activity of the local ACE system of experimental vein grafts was examined in this study. The right carotid artery was divided and bypassed in 21 New Zealand White rabbits, using the right external jugular vein. The left external jugular vein was used as a control. Veins and vein grafts were harvested after 14 days. Rings from both vessels were studied in vitro under isometric tension, and dose-response curves to AI and AII were obtained. AI responses were also measured in the presence of captopril. The tissue concentrations of ACE in both vessels were estimated by spectrophotometry and were localized by immunohistochemistry. The responses of the veins to AI and AII were multiphasic, whereas the responses of vein grafts were sigmoid-shaped. Incubation of vein grafts with captopril significantly decreased the sensitivity to AI (p < 0.0001). Immunohistochemical localization identified ACE in the endothelial layer of the veins and vein grafts, but also at a greater density in the intimal hyperplasia of the vein graft. The concentration of ACE was 1.92 +/- 0.16 U/g (wet weight; mean +/- SEM, n = 9) in vein grafts and 1.39 +/- 0.05 U/g in the veins (38% increase, p < 0.05, n = 9).(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of perioperative storage solutions on long-term vein graft function and morphology

It has been shown that suboptimal preparation of a vein graft prior to its insertion results in immediate morphologic and functional damage to the endothelial cells but not to the underlying smooth muscle cells. However, little is known about whether such perioperative injury to the vein grafts influences the subsequent development of intimal hyperplasia and smooth muscle cell contractility. This study examines the influence of storage in saline solution or Ringer's lactate on the development of intimal hyperplasia and vasomotor function in experimental vein grafts. Twenty-six New Zealand white rabbits had a carotid vein bypass graft performed after the veins had been immersed (15 minutes) in either heparinized saline solution (Sal; n = 13) or Ringer's lactate (RL; n = 13), and each group was harvested after 28 days for either histologic (n = 8) or functional studies (n = 5; four 5 mm rings/graft). Saline storage of the vein graft resulted in a 38% increase in the thickness of the intimal hyperplasia (113 +/- 2 vs. 83 +/- 2 microns, Sal vs. RL; mean +/- SEM; p < 0.05) without a change in medial thickness (87 +/- 5 vs. 86 +/- 8 microns, Sal vs. RL; p > 0.05). The two sets of vein grafts showed no difference in sensitivity to norepinephrine, serotonin, and bradykinin.(ABSTRACT TRUNCATED AT 250 WORDS)

Structural and functional consequences of bypass grafting with autologous vein

An understanding of the consequences of autologous vein grafting reveals both the reasons why cryopreserved allogenic veins are being used clinically and how they are most likely to be expected to fail. Autologous vein bypass grafts are characterized by a series of distinct biological properties that influences their in vivo patency. Current surgical practice ensures that the endothelium of vein grafts is preserved at the time of implantation and that there is minimal damage to the smooth muscle cells. After implantation, the endothelial cells show varying degrees of morphological changes that are maximal within the first 3 days after grafting. In autografts, extensive endothelial denudation does not appear to occur. During the initial grafting period, the smooth muscle cells change from a contractile phenotype to a synthetic phenotype, migrate from the media, proliferate in the intima, and lay down connective tissue. Thereafter, endothelial cell changes regress and the smooth muscle cells return to their contractile phenotype. Perioperative manipulation of vein grafts results in decreased endothelial cell function but preservation of smooth muscle cell responsiveness. Postoperatively endothelial cell-mediated relaxation to acetylcholine is lost and smooth muscle cell contractility is decreased. Within 7 days after implantation, smooth muscle cell contractility returns and, with time, becomes markedly greater than that of the control vein. Endothelium-mediated relaxation to acetylcholine never returns in vein grafts and this loss of endothelial cell function appears to be related to receptor-coupled G-protein defects. Smooth muscle cell contractility remains abnormal. Many of the intimal hyperplastic lesions in vein grafts progress to stenosis or become sites of accelerated atherosclerosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Experimental hypercholesterolemia in rabbits induces cavernosal atherosclerosis with endothelial and smooth muscle cell dysfunction

Hypercholesterolemia and other vascular risk factors for atherosclerosis are commonly associated with impotence. To characterize cavernosal smooth muscle reactivity in hypercholesterolemia, we performed isometric tension studies (with norepinephrine, acetylcholine, papaverine and electrical field stimulation) on isolated strips of corpus cavernosum from rabbits fed a 1% cholesterol diet. To assess the impact of cholesterol reduction, a group of rabbits was fed a cholesterol diet for 4 weeks and was then returned to a normal diet for 4 weeks before testing. Potential structure-function relationships were delineated by ultrastructural evaluation with transmission electron microscopy (TEM). All forms of cavernosal relaxation, including papaverine relaxation, were impaired with hypercholesterolemia, and norepinephrine contraction was augmented. In addition, ultrastructural evidence of an early atherosclerotic process in the cavernosal sinusoids was detected. Importantly, reduction of elevated serum cholesterol normalized cavernosal relaxation, including that of papaverine, and decreased the sensitivity to norepinephrine, thereby suggesting that cavernosal smooth muscle dysfunction in hypercholesterolemia is reversible.

The vascular endothelium. A new horizon

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Regression of intimal hyperplasia with restoration of endothelium-dependent relaxing factor-mediated relaxation in experimental vein grafts

BACKGROUND

The reversibility of the morphologic and functional alterations that occur in veins transplanted into the arterial circulation was examined in this study.

METHODS

Common carotid vein bypass grafts (VG) were performed in 20 male New Zealand White rabbits. Ten VG and jugular veins (CV) were harvested after 14 days, and ten VG were reimplanted as venovenous bypass grafts (REV) and harvested after an additional 14 days. Vessels were taken for structural or isometric tension studies to norepinephrine, serotonin, and bradykinin and to acetylcholine and sodium nitroprusside after precontraction.

RESULTS

There was a decrease in the thickness of the intima (p = 0.02) and the media (p = 0.002) in REV compared with VG. In REV, sensitivity to norepinephrine decreased (p = 0.0007) with a reduced maximal tension to norepinephrine (p = 0.02) and to serotonin (p = 0.0001). Bradykinin sensitivity increased in REV (p = 0.003 vs VG) and was greater than in CV. Only the precontracted CV and REV relaxed to acetylcholine. All tissues relaxed to sodium nitroprusside.

CONCLUSIONS

This study suggests that intimal hyperplasia can be reversed with restoration of endothelium-dependent relaxing factor-mediated relaxation but that only a partial regression of the contractile abnormalities can be achieved.