Endometriosis and spontaneous abortion rate: a cohort study in infertile women

Oxidative stress is believed to play an important role in the development of vascular complications associated with diabetes mellitus. In this study, we examined the efficacy of long-term treatment with the antioxidant, N-acetylcysteine, in preventing the development of defective endothelium-dependent relaxation in streptozotocin-induced, Sprague-Dawley diabetic rats. At 48 h after injection of streptozotocin, a portion of diabetic rats received 250 mg/L N-acetylcysteine in drinking water for a total duration of 8 weeks. Oral administration did not alter the increase in blood glucose or the reduction in serum insulin but did modestly reduce total glycosylated hemoglobin. In precontracted thoracic aortic rings suspended in isolated tissue baths, endothelium-dependent relaxation to acetylcholine was impaired in diabetic rings compared with control rings. Endothelium-independent relaxation to nitroglycerin was unaltered. Long-term oral administration of N-acetylcysteine did not alter responses to nitroglycerin but completely prevented the defective relaxation to acetylcholine. These studies indicate a dissociation between glycemic control and correction of endothelial dysfunction and suggest that long-term exposure to reactive oxygen subsequent to diabetes rather than hyperglycemia per se is responsible for the development of endothelial dysfunction in diabetes mellitus.     

Long-term treatment in vivo with NOX-101, a scavenger of nitric oxide, prevents diabetes-induced endothelial dysfunction

Substantial evidence exists that diabetes results in impaired endothelial dysfunction suggesting diminished nitric oxide production from diabetic endothelium. It is not known what factors contribute to the development of this defect. In this study, we tested whether chronic treatment in vivo with NOX-101, a water-soluble nitric oxide scavenger, prevents endothelial dysfunction in diabetes. Sprague-Dawley rats were made diabetic by an intravenous injection of streptozotocin. A subgroup of control or diabetic animals received twice daily subcutaneous injections of 80 mg/kg NOX-101 beginning at 48 h after streptozotocin was injected and throughout 8 weeks of diabetes. Body weights and glucose concentrations were monitored weekly. At the end of 8 weeks, blood glucose and glycosylated haemoglobin was raised in diabetic rats but serum insulin concentrations were reduced. Treatment with NOX-101 did not alter glucose or insulin concentrations in control or diabetic rats; however, total glycosylated haemoglobin was partially reduced compared with untreated rats. In a subgroup of 2-week diabetic and age-matched rats fasted for 24 h, NOX-101 abolished total urinary nitrate plus nitrite (an index of nitric oxide production in vivo). In isolated tissue baths, relaxation to the endothelium-dependent vasodilator, acetylcholine, was impaired in diabetic aortic rings and relaxation to nitroglycerin was unaltered. Treatment of control rats with NOX-101 did not alter maximum relaxation to acetylcholine but shifted the response curve slightly to the right. In contrast in diabetic rats, NOX-101 prevented the impairment in endothelium-dependent relaxation but had no effect on relaxation induced by nitroglycerin. These data suggest the possibility that diabetes-induced endothelial dysfunction in diabetes results, in part, from a paradoxical increase in nitric oxide production during the course of the disease. This suggests a novel pathway of vascular complications.     

Liver granulomas in schistosomiasis: mast cell-dependent induction of SCF expression in hepatic stellate cells is mediated by TNF-alpha

Abnormalities of vasomotor tone are characteristic of heart failure. This study was designed to assess the effects of chronic heart failure on endothelium-dependent relaxation in both large conduit arteries and small resistance vessels and to determine whether or not impaired nitric oxide (NO) production is involved. Segments of pulmonary artery (PA), abdominal aorta (AA), and small mesenteric artery (MA) were harvested from rats with heart failure resulting from coronary artery ligation and from sham-operated controls. Organ-bath experiments done in the presence of indomethacin to avoid the influence of vasodilatory prostanoids demonstrated that relaxation to acetylcholine (ACh) was impaired in the PA but not the AA or MA of the group with heart failure. Endothelium-independent relaxation to nitroglycerin was not significantly affected by the development of heart failure. Constriction to prostaglandin (PG) F(2alpha) was enhanced in PA but not in AA or MA segments. Preincubation with N(omega)-nitro-L-arginine (NNA) to inhibit the production of NO increased baseline force in vessels from all three beds, but the effect was greatest in the PA. Although relaxation to ACh was significantly diminished by NNA in the PA, it was not completely abolished. Furthermore, ACh-mediated relaxation in the presence of NAA was still impaired in the group with heart failure compared with the sham-operated control group. NNA had only mild effects on ACh-mediated relaxation in MA. These results demonstrate that (a) the mediators of endothelium-dependent relaxation may vary throughout the arterial circulation, (b) the contribution of NO to endothelium-dependent relaxation is substantial in PA and minimal in mesenteric resistance vessels, (c) endothelium-dependent relaxation is not uniformly impaired throughout the arterial bed by the development of heart failure, and (d) although a defect in NO production may account for enchanced vasoconstriction seen in response to PGF(2alpha), it does not account for the diminished vasodilatory response to ACh in this experimental model of heart failure.     

Impaired endothelium-dependent relaxation in isolated resistance arteries of spontaneously diabetic rats

1. Previous studies have shown that endothelium-dependent relaxation in the aorta of spontaneously diabetic bio bred rats (BB) is impaired. 2. We have investigated noradrenaline (NA) contractility, endothelium-dependent acetylcholine (ACh) and bradykinin (BK) relaxation, and endothelium-independent sodium nitroprusside (SNP) relaxation in mesenteric resistance arteries of recent onset BB rats and established insulin treated BB rats, compared to their age-matched non diabetic controls. 3. There was no significant difference in the maximum contractile response or sensitivity to noradrenaline in either of the diabetic groups compared to their age-matched controls. 4. Incubation with the nitric oxide synthetase inhibitor NG-nitro-L-arginine (L-NOARG) resulted in a significant increase in maximum contractile response to noradrenaline in the recent onset age-matched control group (P < 0.05). Analysis of the whole dose-response curve (using ANOVA for repeated measures with paired t test) showed a significant left-ward shift following the addition of L-NOARG (P < 0.001). A similar but less marked shift (P < 0.01) was evident in vessels from recent onset diabetics. An overall shift in both sensitivity and maximum response was also evident in the age-matched non diabetic controls of the insulin-treated group (P < 0.05). However, by contrast, there was no significant change in sensitivity in the insulin-treated diabetic rats. 5. ACh-induced endothelium-dependent relaxation was significantly impaired in the recent onset diabetic rats compared to their age-matched controls (47 +/- 11% versus 92 +/- 2%, P < 0.05, n = 6), and in the insulin treated diabetic rats (34 +/- 5% versus 75 +/- 6%, P < 0.05, n = 6). The relaxation responses to BK also were significantly impaired in the diabetic rats compared to their age-matched controls (recent onset: 20 +/- 3% versus 72 +/- 7%, P < 0.05, n = 6; insulin treated: 12 +/- 9% versus 68 +/- 7%, P < 0.05, n = 7). 6. Incubation with either the nitric oxide synthetase substrate, U-arginine, or the free radical scavenging enzyme superoxide dismutase (150 mu ml-1) failed to improve the attenuated response of acetylcholine-induced relaxation in the diabetic vessels. 7. Endothelium-dependent relaxation mediated by ACh and BK was significantly attenuated in both the diabetic and control vessels after incubation with L-NOARG. 8. Pretreatment with a cyclo-oxygenase inhibitor, indomethacin, significantly enhanced the relaxation to ACh in both the recent onset and insulin treated diabetic rats (42 +/- 10%, n = 7 versus 64 +/- 7%, n = 7, P < 0.05, and 40 +/- 5%, n = 7 versus 65 +/- 9%, n = 6, P < 0.05). 9. Following endothelium removal, there was a marked impairment in endothelium-dependent relaxation responses to ACh and BK in both the diabetic and control vessels. 10. Incubation with the thromboxane A2 receptor antagonist SQ29548, did not significantly improve the ACh endothelium-dependent relaxation response in the diabetic vessels. 11. Endothelium-independent relaxation to sodium nitroprusside was significantly impaired in the first group of diabetic vessels studied; however, subsequent studies showed no impairment of the sodium nitroprusside response in the diabetic vessels. 12. In conclusion, the ability of the endothelium to regulate vascular contractility is reduced in recent onset diabetic vessels, and significantly impaired in established insulin treated diabetics. Relaxation to the endothelium-dependent vasodilators ACh and BK was impaired in both the recent onset and the established insulin treated diabetics, and the ACh response was significantly improved following pretreatment with indomethacin, suggesting a role for a cyclo-oxygenase-derived vasoconstrictor. Preliminary studies with a thromboxane A2, receptor antagonist, SQ29548 did not significantly improve the impaired relaxation to ACh, indicating that the vasoconstrictor prostanoid is not thromboxane A2.     

15-Hydroxyeicosatetraenoic acid and diabetic endothelial dysfunction in rabbit aorta

We examined the effects of diabetes on eicosanoid metabolism and endothelium-dependent relaxation in isolated aorta from alloxan-induced diabetic rabbits and that from normal rabbits incubated in increased concentrations (44 mM) of glucose in vitro for 6 h. Immunoreactive 15-hydroxyeicosatetraenoic acid (HETE) was assayed in the incubation media of isolated aortic segments. Basal and acetylcholine (ACh)-stimulated release of 15-HETE was significantly greater in aorta of diabetic animals as compared with those of normal rabbits. Incubation of aortic segments from normal rabbits in increased concentrations of glucose caused a significant increase in basal and ACh-stimulated release of 15-HETE; and the release was significantly greater in aortic segments with endothelium than in segments without endothelium. Basal and ACh-stimulated release of 15-HETE was inhibited by indomethacin, a cyclooxygenase inhibitor. 15-HETE caused contractions of aortic rings that were inhibited by the prostaglandin H2 (PGH2) thromboxane A2 (TXA2) receptor blocker SQ-29548, but not by the TXA2 synthase inhibitor carbethoxyhexyl imidazole or indomethacin. Treatment of aortic rings with subthreshold concentrations of 15-HETE impaired ACh-induced relaxation; this was prevented by treatment with SQ-29548. Thus, abnormal release of endothelium-derived 15-HETE may play a role in endothelial cell dysfunction and increased vasoconstriction in diabetes by a mechanism that involves interaction with PGH2/TXA2 receptors.     

Endothelium-dependent hyperpolarization in isolated arteries taken from animals treated with NO-synthase inhibitors

To study the effects of chronic in vivo inhibition of NO synthase on endothelium-dependent hyperpolarization, cell-membrane potential (in individual vascular smooth-muscle cells) and changes in tension (in isolated rings) were recorded from isolated canine coronary arteries and guinea-pig carotid arteries and aortas. In coronary arteries taken from control dogs and contracted with U46619, acetylcholine- and bradykinin-induced endothelium-dependent relaxations, which were unaffected by short-term in vitro exposure to indomethacin but were inhibited partially by L-nitro-arginine (LNA). In coronary arteries taken from dogs treated over the long term in vivo with LNA (30 mg/kg on the first day and 20 mg/kg the 7 following days, i.v.), the response to acetylcholine and bradykinin was inhibited when compared with arteries from control dogs. Short-term in vitro exposure to LNA or indomethacin or both did not influence the effects of either agonist. In these arteries, the hyperpolarizing response to acetylcholine, observed in the presence of LNA and indomethacin, was enhanced, whereas that to bradykinin was partially inhibited. In the guinea pig isolated aorta, the relaxation to bradykinin was abolished by long-term in vivo treatment with L-nitro-arginine-methyl-ester (L-NAME; 1.5 mg/ml, in the drinking water for > or =4 days). In the isolated guinea pig carotid artery studied in the presence of LNA and indomethacin, acetylcholine induced a hyperpolarization that was not significantly affected by long-term in vivo treatment with L-NAME. These findings indicate that endothelium-dependent hyperpolarizations are maintained during long-term inhibition of NO synthase and probably act as a back-up mechanism to elicit endothelium-dependent relaxations.     

Antihypertensive and vasodilator actions of antioxidants in spontaneously hypertensive rats

This study was designed to determine whether the antioxidants ascorbic acid, aminotriazole, and glutathione acutely reduce blood pressure (BP) by endothelium-independent or -dependent vasorelaxation in spontaneously hypertensive rats. Blood pressure of male Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHR) was measured before and 4 h after administration of antioxidants. Thoracic aortic rings with and without endothelium were suspended in organ chambers for isometric tension recordings. Each of the antioxidants, administered in vivo, significantly decreased blood pressure in SHR but had no significant effect on BP in WKY rats. The endothelium-dependent impaired relaxation of SHR aortic rings to acetylcholine (ACh) was improved by prior in vivo administration of each antioxidant. ACh-induced relaxations of aortic rings from WKY was not affected by prior antioxidant treatment. Addition of each antioxidant directly to the organ chamber containing SHR or WKY aortas produced dose- and endothelium-dependent relaxations. Moreover, antioxidant pretreatment of SHR aortic rings significantly potentiated ACh-induced relaxations in these aortas, suggesting that this effect was endothelium dependent. Relaxations induced by the antioxidants alone or by ACh in the presence of antioxidants were inhibited by addition of either xanthine plus xanthine oxidase or nitro-L-arginine. These findings suggest that either excess production of oxidants or a deficiency of antioxidant systems may contribute to the high blood pressure and the endothelium-dependent impairment of vascular relaxation in SHR.     

Free-radical scavengers, thiol-containing reagents and endothelium-dependent relaxation in isolated rat and human resistance arteries

1. Small arteries were isolated from either rat mesentery or human subcutaneous fat, and mounted in a myograph for the measurement of isometric force. 2. Superoxide dismutase, either in the presence or absence of catalase, relaxed noradrenaline-induced tone. This effect was abolished by removal of the endothelium or incubation with an inhibitor of NO synthase, N-omega-nitro-L-arginine methyl ester. Catalase alone had a negligible effect on noradrenaline-induced tone. 3. Captopril, an angiotensin-converting enzyme inhibitor and putative free-radical scavenger, did not relax pre-contracted isolated vessels. N-Acetylcysteine caused an endothelium-independent relaxation of rat vessels. Similar effects were observed in human vessels. 4. Acetylcholine induced a concentration-dependent relaxation of isolated resistance arteries, which was inhibited by removal of the endothelium or N-omega-nitro-L-arginine methyl ester, but unaffected by indomethacin. Preincubation with captopril, N-acetylcysteine or catalase alone did not alter the acetylcholine concentration-response relationship, but superoxide dismutase in combination with catalase enhanced responses to acetylcholine, causing a six-fold increase in potency. 5. Superoxide dismutase causes endothelium-dependent relaxation of resistance arteries and potentiates responses to acetylcholine. This action is probably due to the ability of the enzyme to scavenge superoxide anions which inhibit endothelium-dependent relaxation. 6. N-Acetylcysteine causes an endothelium-independent relaxation of resistance arteries which is probably unrelated to the putative ability of this compound to scavenge superoxide radicals and may reflect a direct action on vascular smooth muscle.     

Energetic cost of sexual attractiveness: ultrasonic advertisement in wax moths

PURPOSE: The response of endothelium to ionizing radiation was studied. METHODS AND MATERIALS: The abdominal aorta in different experimental groups of rats was irradiated, and the response of arterial rings from the irradiated segments to norepinephrine, acetylcholine (ACh), and nitroglycerin (NTG) was studied. Nonirradiated thoracic segments in the same experimental animals were used as as a control for comparisons. Two age-matched nonirradiated control groups were also studied. RESULTS: A poor endothelium-dependent vasodilator response was obtained with ACh in the irradiated rings and also in those not directly irradiated; the endothelium-independent vasodilator response to NTG was preserved during the first 3 days after irradiation. By 6 months, both the endothelium-dependent response and endothelium-independent response were impaired. CONCLUSIONS: Alterations in nitric oxide synthesis and/or release by the endothelium were observed during the early phase of radiation in irradiated and nonirradiated segments. In the delayed phase of radiation, endothelium-independent muscular relaxation was also affected.     

Lovastatin maintains nitric oxide--but not EDHF-mediated endothelium-dependent relaxation in the hypercholesterolemic rabbit carotid artery

The endothelium contributes to the regulation of vascular tone by producing nitric oxide (NO) and the endothelium-derived hyperpolarising factor (EDHF). In hypercholesterolemia, endothelium-dependent relaxation is impaired but can be restored by treatment with lovastatin (LOVAS). We investigated the effects of LOVAS on NO and EDHF-mediated relaxation. Rabbits were fed 1% cholesterol diet for 4 weeks and 0.5%) cholesterol for the following 12 weeks (CHOL-group). The LOVAS group additionally received 10 mg of lovastatin over the last 12-week period. Experiments were performed in carotid artery rings. Relaxant responses to acetylcholine (ACh) were recorded in the presence of indomethacin. Nitro-L-arginine (NOARG, 100 microM) and potassium chloride (KCl, 35 mM) were used to differentiate between NO- and EDHF-mediated relaxations. Cholesterol impaired ACh-induced relaxations and this effect was prevented by LOVAS (control 100+/-1%, CHOL 81+/-6%, LOVAS 98+/-1%). In the presence of NOARG, relaxations to ACh were not different between the LOVAS and CHOL groups (control 78+/-4%, CHOL 64+/-6%, LOVAS 64+/-5%). When KCl was used, ACh-induced relaxations were similar in the LOVAS and control group (control 75+/-5%, CHOL 49+/-6%, LOVAS 76+/-2%). In arteries treated with NOARG and KCl together, no relaxations were observed. Relaxations of arteries from the control group were not affected by 18 h preincubation with lovastatin (10 microM). Lovastatin selectively maintains nitric oxide-mediated endothelium-dependent relaxation in hypercholesterolemic rabbit carotid arteries.     

Altered vasodilator response of coronary microvasculature in pacing-induced congestive heart failure

To characterize vasodilator capacity of small coronary arteries (200-350 microm diameter) in the setting of congestive heart failure, we examined relaxation responses to acetylcholine (10(-9)-10(-4) M) and nitroglycerin (10(-9)-10(-4) M), in the absence and presence of the nitric oxide precursor, L-arginine (10(-4) M). Congestive heart failure was reliably induced in dogs by rapid ventricular pacing (250 beats.min(-1) for 4 weeks). Maximum relaxations (means +/- S.E.) to each vasodilator are expressed as a percentage of the relaxation response to papaverine (10(-4) M). Relaxation responses to the endothelium-dependent relaxing agent, acetylcholine, were not altered at heart failure, or in the presence of L-arginine. Contrary to acetylcholine, relaxations to nitroglycerin were significantly enhanced in heart failure compared to control (83 +/- 25% vs. 25 +/- 6%, respectively, P < 0.05). Although L-arginine, alone, did not cause any vasodilator response in coronary microvessels, it was able to potentiate nitroglycerin relaxations at control (no L-arginine: 25 +/- 6% vs. L-arginine: 135 +/- 66%). In contrast, at heart failure, L-arginine diminished nitroglycerin relaxations (no L-arginine: 83 +/- 25%, vs. L-arginine: 48 +/- 15%). These data indicate a unique vasodilator profile in small coronary arteries at heart failure: endothelium-dependent relaxations are unaltered, whereas responses to nitroglycerin are augmented. Addition of the nitric oxide precursor, L-arginine, did not affect acetylcholine relaxation, yet surprisingly had a differential effect in response to nitroglycerin. Moreover, inhibition of nitric oxide synthase with N(omega)-nitro-L-arginine elicited concentration-dependent constriction in heart failure but not control coronary microvessels. In summary, our study suggests an important role for nitric oxide in vasodilator control of coronary microvessels, which may modify nitrovasodilator therapy in congestive heart failure.     

In vitro characterization of tachykinin NK2-receptors modulating motor responses of human colonic muscle strips

BACKGROUND: Endothelium plays a key role in graft patency. My colleagues and I have developed a verapamil+nitroglycerin solution (balanced to pH 7.4) to prepare the radial artery without mechanical distention or dilation and have reported the efficacy of its antispastic action. This study was designed to investigate whether using this solution as part of the University of Hong Kong protocol to prepare the radial artery is more efficacious than papaverine solution in preserving endothelial function. METHODS: Ring segments of the radial artery taken from 25 patients undergoing coronary artery bypass grafting were studied in organ chambers. The endothelium-dependent relaxation, as the index of endothelial function, was examined by two mechanisms-receptor-mediated relaxation (by acetylcholine) and non-receptor-mediated relaxation (by calcium ionophore A23187) in U46619-induced contraction (10 nmol/L). RESULTS: In the relaxation induced by either acetylcholine (27.3% +/- 5.0% [n = 7] vs 23.9% +/- 3.9% [n = 6],p = 0.6) or A23187 (62.9% +/- 6.0% [n = 13] vs 62.3% +/- 8.4% [n = 6],p = 0.96), there was no significant difference between the control radial arteries and those treated with the verapamil+nitroglycerin solution. In the papaverine-treated rings, acetylcholine-mediated relaxation was abolished (3.3% +/- 2.6% vs 23.9% +/- 3.9%,p < 0.001) and A23187-mediated relaxation was significantly reduced (39.7% +/- 5.2% vs 62.3% +/- 8.4%, p = 0.02) compared with verapamil+nitroglycerin treatment. CONCLUSION: Use of verapamil+nitroglycerin solution to prepare the radial artery maximally preserves endothelial function. In contrast, papaverine impairs this function. Verapamil+nitroglycerin solution may be effectively and safely used to prepare the radial artery for coronary artery bypass grafting.     

Impairment of endothelial function induced by glyc-oxidized lipoprotein a [Lp(a)]

Diabetic patients develop endothelial dysfunction early in the course of the disease. Atherogenic lipoproteins such as LDL and Lp(a) are important risk factors for endothelial dysfunction and undergo nonenzymatic glycation in hyperglycaemia. Here we assessed whether glycation of Lp(a) potentiates its damaging influence on endothelial function. Human Lp(a) was glycated by dialyzation for 7 days against buffer containing 200 mmol/l glucose, or sham-treated without glucose and oxidized by incubation with Cu++. The degree of glycation accounted to 32 +/- 4%, and glycation rendered Lp(a) more susceptible to oxidative modification when exposed to Cu++. Isolated rings of rabbit aorta were superfused with physiological salt solution, and isometric tension was recorded. Incubation of the aortic rings with sham-treated or with 30 microg/ml glycated Lp(a), not oxidized, had no influence on acetylcholine-induced, endothelium-dependent relaxation. Exposure of the aortic rings to 30 microg/ml oxidized non-glycated (ox) Lp(a) caused a significant inhibition (19% at 1 microM acetylcholine) of the endothelium-dependent relaxation. Incubation of aortic rings with 30 microg/ml oxidized glycated (glyc-ox) Lp(a) attenuated endothelium-dependent relaxation more potently than oxLp(a) (by 34% at 1 microM acetylcholine). The presence of diethyl-dithio-carbamate (DDC), an inhibitor of the endogenous superoxide dismutase (SOD), potentiated the inhibition of relaxation induced by oxLp(a) and by glyc-oxLp(a) [38% inhibition at 1 microM acetylcholine for oxLp(a), and 49% inhibition at 1 microM acetylcholine for glyc-oxLp(a)]. Co-incubation with the O2- scavenger 4,5-dihydroxy-1,3-benzene disulfonic acid disodium salt (TIRON) prevented the inhibition of relaxation by the oxidized lipoproteins, suggesting that enhanced NO-inactivation by O2- could be the underlying mechanism for the impairment of endothelium-dependent dilations by ox- and glyc-oxLp(a). The concentration of lysophosphatidycholine, a lipoprotein oxidation product and stimulus for O2- formation, was significantly enhanced in oxLp(a) and in glyc-oxLp(a) compared to native lipoproteins. Conclusion: Glycation enhances the endothelium-damaging influence of oxLp(a), presumably by enhancing oxidative stress. The likely mechanism for attenuation of endothelium-dependent dilations is increased formation of O2-, resulting in inactivation of nitric oxide. This mechanism may play an important role in diabetic patients and may contribute to disturbed organ perfusion.     

Testosterone worsens endothelial dysfunction associated with hypercholesterolemia and environmental tobacco smoke exposure in male rabbit aorta

OBJECTIVES: To assess the effects of interaction of sex hormones, hypercholesterolemia (HC) and environmental tobacco smoke (ETS) exposure on endothelium-dependent relaxation, we examined vascular reactivity in vitro in an animal model of atherogenesis. BACKGROUND: Animal and human studies indicate the presence of interactions between classic coronary artery disease risk factors and endothelium-dependent relaxation. Sex hormones have also been shown to influence release of endothelium-derived relaxing factor. METHODS: New Zealand White rabbits were randomized to receive either an HC diet (n = 8) or ETS exposure plus HC diet (n = 8). Eight rabbits receiving a normal diet, without exposure to ETS, served as the control group. The HC diet consisted of 3% soybean oil and 0.3% cholesterol by weight over 13 weeks. The source of ETS was sidestream smoke of 4 cigarettes/15 min, 6 h/day, 5 days/week over 10 weeks in a smoking chamber. Rabbits were killed, and fresh aortic rings were harvested and maintained in oxygenated Krebs solution in an organ bath at 37 degrees C. Rings were precontracted with norepinephrine and exposed to acetylcholine in increasing doses, and isometric tension was recorded. Rings were also exposed to physiologic concentrations (1 nmol/liter) of either 17-beta-estradiol, testosterone or progesterone before pre-contraction with norepinephrine and relaxation with acetylcholine. Endothelium-independent relaxation was studied using nitroglycerin. The surface area of the ring covered by lipids was measured by Sudan IV staining. RESULTS: HC and ETS significantly reduced endothelium-dependent relaxation (p = 0.01 and p < 0.0005, respectively) and caused atherogenesis (p < 0.0005 and p = 0.047, respectively) but did not affect endothelium-independent relaxation. Incubation with estradiol and estradiol plus progesterone did not influence endothelium-dependent relaxation. Testosterone reduced endothelium-dependent relaxation (p = 0.049) and augmented the endothelial dysfunction associated with ETS exposure and HC (p = 0.03). CONCLUSIONS: Both HC and ETS are atherogenic and impair endothelial function but do not affect endothelium-independent relaxation. Physiologic levels of estradiol and estradiol plus progesterone do not affect endothelium-dependent relaxation. Physiologic levels of testosterone impair relaxation and augment the endothelial dysfunction associated with ETS exposure and HC.     

Effects of hydroxyethyl starch-deferoxamine on arachidonic acid metabolism and small bowel wall perfusion in early sepsis

The effects of hydroxyethyl starch-conjugated deferoxamine (HES-DFO), a macromolecular iron chelator, were investigated on eicosanoid release and bowel wall perfusion following cecal ligation puncture (CLP) in rats. Animals were randomly given an intravenous dose of 3.0 ml of HES-DFO or either vehicle (HES) or 9.0 ml saline immediately following completion of the CLP procedure. At 30, 60, 120, and 240 min after sepsis induction, blood pressure and bowel perfusion were measured. The animals were sacrificed and blood was collected for subsequent analysis of thromboxane, prostacyclin, and prostaglandin F2 alpha. The tissue content of energy-rich phosphates was determined in small-bowel samples at each time point. The antioxidative HES-DFO therapy did not diminish the eicosanoid release after CLP when compared with either HES-treated or saline-infused rats. However, treatment with the polymeric iron chelator resulted in an impaired bowel wall perfusion that was not reflected in alterations in total adenine nucleotide content or in energy charge. Considering hemodynamic and biochemical endpoints, these results are contradictory to the hypothesis that iron-driven oxygen radicals are major determinants of the eicosanoid release that is elevated following CLP-induced sepsis.     

Possible superoxide radical-induced alteration of vascular reactivity in aortas from streptozotocin-treated rats

We investigated the possible involvement of the superoxide (.O2-) radical in alterations of vascular reactivity and phosphoinositide (PI) turnover in aortas from streptozotocin (STZ)-induced diabetic (4 week) rats. STZ treatment increased the maximal contractile response of the aorta to norepinephrine (NE), phenylephrine (PE) and high K+, whereas the sensitivity remained unaltered. Ca(++)-induced contractions in the presence of maximally effective concentrations of PE and K+ were also augmented after STZ treatment. The increased maximal response was associated with both decreased endothelium-dependent relaxation and increased NE-induced PI turnover. Pyrogallol (PYR), a potent .O2- generating agent, did not affect basal tone or PI turnover but, depending on concentrations, it significantly increased or decreased both the contractile response to PE and NE-induced PI turnover in control aorta. In contrast, PYR decreased NE-induced PI turnover in diabetic aorta. The malondialdehyde content of liver, serum and aorta, and of .O2- from aorta of diabetic rats, were increased significantly. Copper catalyzed oxidation of ascorbic acid resulted in contraction followed by relaxation, depending upon the ascorbic acid concentration in both control and diabetic aorta. Pretreatment with superoxide dismutase (300 U/ml) prevented the PYR-induced potentiation of the PE contraction, but not of NE+PYR-induced PI turnover in control aorta and decreased further NE+PYR-induced PI turnover in diabetic aorta. The present findings indicate that .O2- may be responsible, at least in part, for the impaired endothelial integrity, enhanced alpha adrenergic receptor-mediated PI turnover and augmented contractility, possibly through modification of calcium channels in STZ-induced short-term (4 week) diabetic rat aorta.     

Chronic treatment with losartan ameliorates vascular dysfunction induced by aging in spontaneously hypertensive rats

OBJECTIVE: To evaluate the effects of prolonged treatment with losartan on endothelium-dependent and endothelium-independent relaxations of aortic rings from adult and senescent spontaneously hypertensive rats, and to clarify whether these effects were due to specific mechanisms of the drug or a consequence of its blood-pressure-lowering action. MATERIALS AND METHODS: Adult (aged 5 months) and senescent (aged 20 months) male spontaneously hypertensive rats were treated for 12 consecutive weeks with 10 mg/kg per day losartan. Systolic blood pressure and plasma concentration of nitrates were evaluated. We studied endothelium-dependent and endothelium-independent relaxations and response to angiotensin II of aortic rings from rats of each group. The direct effects of angiotensin II type 1 receptor antagonism on vascular reactivity of aortic rings from untreated adult and senescent rats that had been incubated beforehand with losartan were also studied. RESULTS: Losartan treatment comparably reduced blood pressure and increased plasma concentration of nitrates in rats of both age groups. Responses to acetylcholine and sodium nitroprusside were lower for rings from senescent than they were for rings from adult rats. Constrictor responses to angiotensin II were higher for rings from senescent than they were for rings from adult rats. Treatment with losartan increased the magnitude of relaxations in response to acetylcholine for rings from rats in both groups, but increased the magnitude of relaxations in response to nitroprusside only for rings from senescent spontaneously hypertensive rats. Incubation beforehand of aortic rings from untreated rats with losartan enhanced magnitude of relaxations in response both to acetylcholine and to nitroprusside only for rings from senescent spontaneously hypertensive rats. CONCLUSIONS: The consequences of aging for endothelium-dependent and endothelium-independent relaxations of rings from spontaneously hypertensive rats are ameliorated by losartan treatment, suggesting that angiotensin II plays a role via type 1 receptors. The effects of losartan on senescent spontaneously hypertensive rats were due not only to its blood-pressure-lowering action but also to the blockade of specific mechanisms derived from angiotensin II type 1 receptor antagonism, which might involve an increase in availability of NO.     

Effects of preanesthetic and anesthetic drugs on endothelium-dependent responses in the rat aorta

1. Acetylcholine often fails to induce endothelium-dependent relaxation in human vessels in vitro. Due to the fact that most of these vessels come from surgery, we examined the influence of drugs used in anesthesia on endothelium-dependent responses in rat aorta. 2. Groups of male Wistar rats of the following treatments were utilized: P group, diazepam+promethazine+atropine; I group, pentothal+succinylcholine; IG group, halothane+nitrous oxide; M group, morphine+pancuronium; C group, untreated rats. Dose-response curves to noradrenaline and acetylcholine were determined in rat aorta in vitro, in the presence and absence of endothelium. 3. Acetylcholine induced more relaxation (P < 0.05) in the rat aorta of IG group compared with that of the C group. 4. In the rat aorta from P and IG groups, the contractions produced by several concentrations of noradrenaline were significantly smaller (P < 0.05) when the endothelium was removed. Similar effects occurred in aorta strips of animals previously treated with either atropine, promethazine, cimetidine or halothane. 5. Our results suggest that drugs currently used in anesthesia interfere with some endothelium-dependent effects on isolated rat aorta but according to these results they do not seem to be responsible for the lack of acetylcholine relaxation sometimes described in human vessels in vitro.     

Nephrotoxicity of acyclovir and ganciclovir in rats: evaluation of glomerular hemodynamics

Effects of pretreatment with thiopental on endothelium-dependent vasodilator responses elicited by drugs in rat aortic rings were investigated. The vasodilators employed were acetylcholine and histamine (endothelium- and receptor-dependent), A23187 (endothelium-dependent but receptor-independent) and sodium nitroprusside (endothelium-independent); they were tested 15 or 60 min after aortic preparations were exposed during 15 min to thiopental. Pretreatment with the barbiturate reversibly inhibited relaxation elicited by either acetylcholine and histamine, but a high concentration of the anesthetic was needed (3.1 mg/ml). On the contrary, thiopental did not modify the relaxation elicited by sodium nitroprusside or A23187. In addition, the barbiturate inhibited basal and acetylcholine-stimulated production of nitrites (an indicator of nitric oxide output) in aortic rings. In conclusion, thiopental inhibited the endothelium-dependent relaxation elicited by either acetylcholine or histamine. Although the barbiturate also inhibited nitric oxide production, the reduction in the relaxant response provoked by it does not seem to be the result of direct guanylate cyclase or nitric oxide synthase alterations, since thiopental did not modify the effect of sodium nitroprusside or A23187. Disturbances elicited by thiopental on endothelial receptors or on signal transduction elements may indirectly provoke nitric oxide synthase inhibition.     

Smoking impairs the activity of endothelial nitric oxide synthase in saphenous vein

Smoking impairs the endothelium-dependent relaxation of arteries and veins, with the maximum relaxation in response to the calcium ionophore A23187 of saphenous vein rings being reduced from 53 +/- 4% in nonsmokers to 27 +/- 5% in smokers. We have investigated whether this endothelial dysfunction was attributable to altered activity or concentration of nitric oxide synthase (NOS). The concentration of NOS in saphenous vein endothelium, determined by Western blotting and immunohistochemistry, was not different in nonsmokers and smokers. Nitrite production from vein strips stimulated with A23187 was higher in nonsmokers (median 23.6 nmol.cm-2.h-1) than smokers (median 3.3 nmol.cm-2.h-1), P=.001, this difference being abolished when vein strips were preincubated in the presence of NG-monomethyl-L-arginine. Organ chamber studies to monitor the endothelium-dependent relaxation of vein rings in response to A23187 showed that preincubation of rings from smokers with either L-arginine (3mmol/L) or superoxide dismutase (250 U/mL) did not improve the maximum relaxation. In contrast, preincubation of vein rings from smokers with 20 micromol/L tetrahydrobiopterin increased the maximum relaxation from 27 +/- 5% to 51 +/- 6%, P=.01. Preincubation of vein from smokers with tetrahydrobiopterin also significantly increased nitrite and cGMP production in response to stimulation with A23187. The impaired endothelium-dependent relaxation of saphenous vein rings from smokers appears to be caused by a reduction in the activity of endothelial NOS that is attributable to an inadequate supply of the coenzyme tetrahydrobiopterin.