Chronic vasopeptidase inhibition restores endothelin-converting enzyme activity and normalizes endothelin levels in salt-induced hypertension.

BACKGROUND: Vasopeptidase inhibition (VPI) represents a new therapeutic principle including both inhibition of angiotensin-converting enzyme (ACE) and neutral endopeptidase (NEP). The present study investigated the effect of the vasopeptidase inhibitor omapatrilat on endothelin-1 (ET-1)-mediated vascular function in salt-induced hypertension. METHODS: Dahl salt-sensitive rats (n=6/group) on standard or salt-enriched (4% NaCl) chow were treated for 8 weeks with either omapatrilat (36+/-4 mg/kg/day), captopril (94+/-2 mg/kg/day) or placebo. Aortic and renal artery segments were isolated and suspended in organ chambers for isometric tension recording. Functional endothelin-converting enzyme (ECE) activity was assessed in native segments and after preincubation with omapatrilat. Furthermore, vascular ECE protein levels as well as plasma and tissue ET-1 levels were determined. RESULTS: The increase in systolic blood pressure of salt-fed rats was prevented by omapatrilat and captopril to a comparable degree. In salt-induced hypertension, functional ECE activity (calculated as the ratio of the contraction to big ET-1 divided by the contraction to ET-1) in renal arteries (0.46+/-0.05) and in aorta (0.68+/-0.05) was reduced as compared with control animals (0.9+/-0.05 and 0.99+/-0.04, respectively; P<0.05). While omapatrilat in vitro blunted the response to big endothelin-1 (big ET-1) and diminished ECE activity further (P<0.01 vs native segments), chronic treatment with omapatrilat in vivo restored contractions to ET-1 (120+/-6%) and big ET-1 (98+/-9%) in renal arteries, and therefore normalized renovascular ECE activity. In addition, omapatrilat normalized plasma ET-1 concentrations (12.9+/-1.2 vs 16.6+/-1.4 pg/ml on high salt diet; P<0.05) and renovascular ECE protein levels. CONCLUSIONS: In salt-induced hypertension, vasopeptidase inhibition restores alterations in the endothelin system, such as renovascular ECE activity and responsiveness to ET-1 and big ET-1 with chronic but not acute in vitro application. Thus, the beneficial effects of vasopeptidase inhibition may reflect a resetting of cardiovascular control systems and therefore may be particularly suited to treat hypertension and heart failure.     

一氧化氮合酶、内皮素在门脉高压大鼠肠粘膜中的表达变化

目的　探讨一氧化氮合酶和内皮素 -1在门脉高压大鼠肠粘膜中的表达情况。方法　2 0只雄性SD大鼠随机分为实验组与对照组 ,实验组行门静脉两步结扎加左肾上腺静脉结扎 ;应用免疫组化SP染色法检测iNOS、ecNOS及ET -1在大鼠小肠和结肠粘膜中的表达情况。结果　门静脉完全结扎后两周 ,实验组大鼠门静脉压力较对照组明显增高 ;iNOS、ecNOS及ET -1在小肠粘膜中表达强度较对照组增强 ,iNOS及ET -1在结肠粘膜中表达较对照组增强。结论　门脉高压大鼠小肠、结肠粘膜局部病变中iNOS、ecNOS及ET -1的表达不完全一致     

Increase in nitric oxide bioavailability improves endothelial function in endothelin-1 transgenic mice.

BACKGROUND: Endothelin-1 (ET-1) has been described as a very potent vasoconstrictor. Nevertheless, transgenic mice overexpressing ET-1 have been shown to exhibit normal blood pressure. We thus hypothesized that vascular ET-1 effects may be antagonized by increased activity of other regulatory systems, such as the increase in bioavailability of the endothelial counterpart of ET-1, nitric oxide (NO). METHODS: Endothelium-dependent and -independent vascular function was assessed as relaxation/contraction of isolated preconstricted aortic rings to acetylcholine (10(-10)-10(-4) mol/l), sodium nitroprusside (10(-10)-10(-4) mol/l), ET-1 (10(-10)-10(-7) mol/l) and big ET-1 (10(-10)-10(-7) mol/l), respectively, in ET-1 transgenic mice and corresponding controls. To unmask the impact of the NO system, we furthermore analysed vessel rings incubated in vitro with the NO-synthase inhibitor L-N(G)-nitroarginine methyl ester (L-NAME, 10(-4) mol/l). RESULTS: Maximum endothelium-dependent relaxation was enhanced in ET-1 transgenic mice (93+/-3% vs 84+/-4% for wild-type littermates; P<0.05) and was inhibited by preincubation with L-NAME in both ET-transgenic mice and wild-type littermates (11+/-5% vs 9+/-4% maximum relaxation, respectively). Endothelium-independent relaxation was similar among all groups. Maximum vascular contraction to ET-1 and big ET-1 was reduced in ET-1 transgenic mice (P<0.05 vs wild-type littermates). Preincubation with L-NAME reduced this difference, indicating the involvement of augmented NO availability. Correspondingly, urinary nitrate/nitrite excretion was significantly elevated in ET-1 transgenic mice. CONCLUSIONS: These data suggest that in transgenic mice overexpressing ET-1, increased NO bioavailability counteracts the contractile potency of elevated ET-1 levels and leads to an improvement of endothelium-dependent relaxation. Thus, in the presence of an activated ET system, up-regulation of NO production may be capable of maintaining vascular tone in a normal range and therefore may prevent the development of hypertension.     

选择性醛固酮受体拮抗剂对肾血管性高血压的作用及机制

目的 研究选择性醛固酮受体拮抗剂eplererNONE(EP)对肾血管性高血压的作用机制。方法 Wistar大鼠48只,随机分6组,1组为假手术组,其余5组均为2K-1C肾血管性高血压模型,再分为对照组、EP早给药组、EP晚给药组、洛沙坦(LO)早给药组和LO晚给药组。实验前及术后每2周检测收缩压(SBP)及尿蛋白排泄率(UPE)。对主动脉、心脏及肾脏进行病理组织学检查及一氧化氮合酶(ecNOS)基因表达的分析。结果 与假手术组比较,第10周对照组收缩压(SBP)明显增加;LO及EP早给药组SBP明显降低;LO及EP晚给药组SBP没有明显降低。与假手术组比较,对照组大鼠出现明显蛋白尿;LO早给药组和EP早给药组蛋白尿明显减少(P<0.05及P<0.01);LO及EP晚给药组蛋白尿没有明显降低。与对照组比较,EP早给药组明显增加心脏ecNOS基因表达;两EP给药组主动脉ecNOS基因表达明显增加;两LO给药组对心脏及主动脉ecNOS基因表达无明显影响;LO早给药组及两EP给药组肾脏ecNOS基因表达明显增加。结论 EP早期给药治疗明显降低2K-1C肾血管性高血压大鼠的收缩压和蛋白尿,其机制可能与心、肾、主动脉ecNOS基因表达上调有关。     

Analysis of the Correlation of Plasma NO and ET-1 Levels in Rats With Acute Mesenteric Ischemia

Mesenteric ischemia is a devastating disease process that frequently challenges clinicians. To enhance the early diagnosis of gut ischemia and judgment of its severity, it may be helpful to detect the unusual existence or increase in biomarkers in the body fluid. The aim of the present study was to evaluate the correlation of plasma nitric oxide (NO) and endothelin-1 (ET-1) levels to mesenteric ischemia using an animal model. Acute mesenteric ischemia (AMI) was produced experimentally by occlusion of the mesenteric vessels in the terminal ileum by the tenting of a thread. The determination of plasma NO and ET-1 levels were obtained before operation (T0, baseline value), and at 10 (T10), 20 (T20), 30 (T30), and 60 (T60) min after the creation of AMI. Sham-operated rats served as controls. After 30 min of experiments, the plasma NO and ET-1 levels were significantly higher in the AMI group than in the control group (both p <. 01). Both the plasma NO and ET-1 levels in AMI group increased significantly after 30 min of ischemia (both p <. 001 vs. respective baseline value), and they were 60% and 84% above the baseline value, respectively. In addition, ischemic intestinal injury was confirmed by the significantly elevated histological scores in the AMI group after 60 min of ischemia (p <. 001). Our preliminary results suggest the possibility of important insights regarding NO and ET-1 changes into the mechanism of pathogenesis in AMI in rats. The increases in plasma NO and ET-1 levels may potentially be noninvasive biomarkers for the early detection of this disease.     

Endothelin-1 and Nitric Oxide in Patients on Chronic Hemodialysis

Aim. To establish the role of endothelin-1 and nitric oxide in the pathogenesis of hypertension in patients on chronic aemodyalisis by correlating endothelin-1 and NO plasma concentrations to the level of arterial hypertension with respect to angiotensin-converting enzyme (ACE) inhibitor therapy. Methods. We determined plasma concentrations of endothelin-1 and NO in patients on chronic hemodialysis (CHD) before and after hemodialysis treatment. The study included 30 CHD patients and 20 healthy participants as controls. Correlation to blood pressure was determined, as well as the effect of ACE inhibitors on the relationship between both endothelin-1 and NO in correlation with arterial hypertension. Main findings.Endothelin-1 plasma concentration was significantly higher in CHD patients before hemodialysis treatment than in healthy controls. Endothelin-1 plasma concentration was also significantly higher in CHD patients after hemodialysis than in healthy controls. There was a significant decrease in endothelin-1 plasma concentration after hemodialysis in comparison with its values before hemodialysis. In CHD patients, a positive correlation was found between endothelin-1 plasma concentration and systolic blood pressure after hemodialysis, irrespective of ACE inhibitors therapy. In CHD patients taking ACE inhibitors, systolic blood pressure increased with increasing endothelin-1 plasma concentration before as well as after hemodialysis. In patients taking ACE inhibitors, there was a tendency for diastolic blood pressure to increase with an increase in endothelin-1 plasma concentration after hemodialysis and to decrease with an increase in NO plasma concentration. Conclusion. NO and endothelin-1 play a significant role in etiology of the hemodynamic changes of blood pressure during the dialysis.     

Cyclosporine Induces Endothelin-1 mRNA Synthesis and Nitric Oxide Production in Human Proximal Tubular Epithelial Cell Cultures

Background. Cyclosporine (CsA) is implicated in the development of chronic allograft nephropathy, which is related to reduced long-term allograft survival. The activation of tubular epithelial cells is involved in the renal scarring process via stimulation of factors such as endothelin-1 (ET-1) and nitric oxide (NO). The effect of CsA on the activation of tubular epithelial cells towards increased production of ET-1 and NO was investigated in this study. Methods. Human tubular epithelial cells (HK-2) were cultured in the presence of CsA at different concentrations (125, 250, 500, and 1,000 ng/mL). ET-1 m-RNA and NO production were measured using RT-PCR and Griess method, respectively. The cytotoxic effect of CsA was examined by the MTT method and cell count. Results. A statistically significant and dose-dependent cytotoxic effect of cyclosporine on HK-2 cells was observed. A dose-dependent up-regulation of ET-1 mRNA production and NO accumulation was observed under the influence of CsA. Conclusion. Increased synthesis of endothelin-1 mRNA and nitric oxide as well as a significant cytotoxic effect on tubular epithelial cells under the influence of CsA might be related to the development of CsA nephrotoxicity.     

NOS、ET-1在血吸虫病门静脉高压兔肺组织中的表达和意义

目的　探讨内皮素 (endothelin -1,ET -1)、一氧化氮 (NO)在血吸虫病门静脉高压性肺血管病变发病机制中的作用。方法　运用腹部敷贴法感染血吸虫尾蚴形成血吸虫病肝硬化门静脉高压症动物模型 ,模型组 (M组 ) 10只和正常对照组 (N组 ) 10只 ,应用免疫组织化学法对动物模型的肺组织中的ET -1、一氧化氮合酶 (nitricoxidesynthase ,NOS)进行定位性研究 ,并以正常兔作对照。结果　感染血吸虫尾蚴 12 0d后 ,肝硬化门静脉高压症动物模型成功 ,模型组肺组织中ET -1、NOS阳性细胞的表达均明显增多 ,染色增强 ,计算机图像定量分析示两组光灰度值和光密度值均具有显著性差异 (P <0 .0 1)。结论　ET -1、NOS在血吸虫病门静脉高压兔肺血管中的表达明显增强 ,表明ET -1、NO在血吸虫病门脉高压性肺血管病变发病机制中具有重要意义。     

Supplementation with a low dose of L-arginine reduces blood pressure and endothelin-1 production in hypertensive uraemic rats.

BACKGROUND: We documented recently that increased endothelin-1 (ET-1) production in blood vessels and glomeruli of uraemic rats plays a crucial role in the development of hypertension and the progression of chronic renal failure. Normally, biological effects and local production of ET-1 are attenuated by the immediate release of nitric oxide (NO). Increasing evidence suggest, however, that NO release is impaired in chronic renal failure. We investigated whether supplementation with L-arginine, the natural precursor of NO, improves NO synthesis in uraemic rats with reduced renal mass and modulates vascular and renal ET-1 production as well as blood pressure and renal failure progression. METHODS: One week after surgical renal mass reduction, the uraemic and sham-operated animals received either no treatment or 0.1% L-arginine in drinking water for 5 weeks. In another series of experiments, uraemic rats received 1% L-arginine for 5 weeks. Immunoreactive-ET-1 (ir-ET-1) levels in plasma, urine, and vascular and renal tissue preparations was measured by radioimmunoassay after sample extraction and purification. RESULTS: Before treatment, systolic blood pressure was significantly elevated in uraemic animals compared to sham-operated controls (156+/-7 vs 111+/-3 mmHg, respectively; P<0.01). Thereafter, systolic blood pressure increased further in uraemic-untreated rats (systolic blood pressure at week 5; 199+/-9 mmHg, P<0.01), whereas it remained similar in uraemic rats supplemented with 0.1% L-arginine (171+/-9 mmHg, NS). At the end of the study, serum creatinine and urea, proteinuria and ir-ET-1 excretion were significantly augmented, while creatinine clearance was reduced in uraemic animals compared to the controls. Ir-ET-1 level was also increased in glomeruli as well as in thoracic aorta, mesenteric arterial bed, and pre-glomerular arteries, and was associated with vascular hypertrophy as assessed by tissue weight. In contrast, ir-ET-1 level was diminished in the renal papilla of uraemic rats. Treatment with 0.1% L-arginine significantly reduced proteinuria and urinary ir-ET-1 excretion (P<0.05) as well as ir-ET-1 level in glomeruli (P<0.01) and in thoracic aorta (P<0.05). These changes were associated with increased plasma NO metabolites NO2/NO3 levels in L-arginine-treated animals (P<0.01) and reduced aortic hypertrophy (P<0.05). In contrast, supplementation with 1% L-arginine had no effect on systolic blood pressure in uraemic rats, but exacerbated proteinuria and urinary ir-ET-1 excretion and increased serum urea (P<0.05) were observed. CONCLUSIONS: These results indicate that improvement of NO release with a low dose but not with a high dose of L-arginine significantly attenuates the development of hypertension and the progression of renal insufficiency in rats with reduced renal mass. These protective effects may be mediated in part by the reduction of vascular and renal ET-1 production.     

Oxygen species in the microvascular environment: regulation of vascular tone and the development of hypertension.

Derangements of the three endothelium-related vasodilator systems (prostaglandins, endothelium-derived hyperpolarizing factor(s) and nitric oxide) cause the endothelial dysfunction observed in hypertension. Free radical-induced nitric oxide degradation plays a crucial role in hypertension. An increase in superoxide producing enzymes such as NAD(P)H oxidase and xanthine oxidase has been demonstrated. Superoxide dismutase may correct endothelial dysfunction in vitro and superoxide dismutase mimetics can lower blood pressure in experimental animals. Antioxidant agents and xanthine oxidase-inhibiting compounds have been used in humans. In addition, the synthesis of vasoconstrictor peroxides derived from the activity of cyclooxygenase in the endothelium and the vascular smooth muscle is stimulated by the OH. radical. Hydrogen peroxide levels are augmented in hypertension, but its role is unclear because recent investigations have shown that this substance may act as a hyperpolarizing factor. It is thought that the therapeutic benefit of anti-hypertensive drugs, such as calcium antagonists and angiotensin-converting enzyme inhibitors, could be in part due to an inhibition of free radical production. A role of superoxide in the endothelial dysfunction and hypertension of chronic renal failure has also been suggested by recent animal experiments.     

葛根素对家兔肝缺血再灌注一氧化氮、内皮素-1的影响

目的观察一氧化氮(NO)、内皮素-1(ET-1)在家兔肝缺血再灌注损伤过程中的变化及葛根素(Pur)对其的影响。方法实验家兔随机分为3组:对照组(C组,n=10)、缺血再灌注组(IR组,n=10)和葛根素治疗组(Pur组,n=10)。分别测定缺血前,缺血第45分钟及再灌注第45分钟时肝组织NO,ET-1含量,用电镜观察家兔HIRI及经Pur保护后的肝组织形态学改变。结果家兔缺血再灌注第45分钟时,与C组、Pur组比较:IR组血浆及组织NO含量均明显较低(P<0.01,P<0.05);IR组血浆及组织ET-1含量明显较高(P<0.01,P<0.05);与IR组比较,Pur组肝组织超微结构明显改善。结论葛根素可通过调节机体NO和ET-1水平而对肝缺血再灌注损伤发挥积极的保护作用。     

Regulation of nitric oxide synthesis in uraemia

Nitric oxide (NO) is a cell-to-cell mediator involved in theregulation of vascular tone and in the mechanisms of host defence.Since uraemic syndrome is characterized by abnormalities inblood pressure and flow and by impairment of white cell function,we studied the regulation of nitric oxide synthase (NOS) activityby uraemic plasma. We used three different cellular types havingdifferent levels of NOS activity: tEnd. 1 murine endothelialcell line transformed by mT oncogene of polyomavirus had a highNOS activityand expressed endothelial-NOS (eNOS) and inducible-NOS(iNOS) isoforms; human endothelial cells from cord umbilicalvein (HUVEC) had low enzymatic activity and expressed only eNOS;finally, J774 murine macrophage line was characterised by iNOSinduced after treatment with cytokines. We demonstrated thatmost (79%) of end-stage uraemic plasma studied inhibited NOSactivity in tEnd.1 and in cytokine induced -J774, whereas theywere ineffective on HUVEC. Twenty percent of plasma samples(14 of 67) activated NOS activity in tEnd.1 and in J774 cells,but not in HUVEC, suggesting the presence of molecule(s) whichinfluence iNOS. The effect of plasma was not dependent on thetype of haemodialysis treatment. A great number of plasmas frompatients with moderate renal failure also inhibited NOS activityin tEnd.1, suggesting that the accumulation of molecules affectingNOS was caused by the renal failure rather than the haemodialytictreatment. However, the haemodialysis modified the effect of plasmas onNOS activity. Plasma taken after haemodialysis session showeda reduced inhibitory activity in tEnd.1 and in some cases itenhanced NOS activity. Simultaneously, molecules reducing NOSactivity accumulated in the ultrafiltrate. The plasma concentrationof N^G-N^G dimethyl-L-arginine (asymmetrical dimethylarginine,ADMA), an inhibitor of NOS, increased in end-stage uraemic patientsand was reduced by haemodialysis. However, the concentrationsreached in uraemic plasmas were lower than the ADMA ICM₅₀ ontEnd.1 NOS, indicating that this compound contributes with othermolecules to the inhibitory effect of uraemic plasma. Haemodialysisreduced also the enhanced effect exerted by some plasmas onNOS in J774. Therefore, the effect of endstage uraemic plasmaon NOS activity derive from the balance between inhibitors andactivators.     

Selective inhibition of endothelin receptor A as an anti-angiogenic and anti-proliferative strategy for human pancreatic cancer

Endothelin-1 (ET-1) plays a major role in tumor proliferation and angiogenesis of various types of cancer acting through endothelin receptors A and B (ETRA and ETRB). The aim of this study was to analyze theET-1/ETRsystem inhumanpancreatic cancer cell linesandto evaluate the effect of a selective endothelin A inhibitor in vitro and in vivo in an orthotopic mouse model. Three different human pancreatic cancer cell lines, MiaPaCa-2, AsPC-1, and Panc-1, were studied. We found that proliferation of human pancreatic carcinoma cells expressing ETRA was significantly reduced with a selective antagonist. Hypoxic conditions led to improved results compared to a normoxic environment (MiaPaCa-2: -53% vs. -18%; AsPC-1: -54% vs. -46%). Proliferation of ETRA negative Panc-1 cells was not decreased. In vivo, the selective ETRA inhibition resulted in reduced angiogenesis as measured by lower microvessel densities (MiaPaCa-2: -47%; AsPC-1: -55%). The blockade of ETRA decreased the volume (MiaPaCa-2: -87%; AsPC-1: -28%) and metastatic spread (MiaPaCa-2: -95.5%; AsPC-1: -27%) of receptorpositive tumors, thereby increasing survival in experimental pancreatic cancer. ETRA blockade did not show an effect on ETRA negative Panc-1 tumors. Therefore, targeting ETRA with a selective antagonist might provide a new approach to reducing proliferation and angiogenesis in human pancreatic cancer. Presented in part at the Forty-Fourth Annual Meeting of The Society for Surgery of the Alimentary Tract, Orlando, Florida, May 18–21, 2003. This work was supported by the R.S. Hirshberg Foundation and the Deutsche Forschungsgemeinschaft (Grant HO 1843/2-1).     

Pulmonary injury in recipients of discordant hepatic and renal xenografts in the dog-to-pig model

Abstract: Work in our lab demonstrated that the early post-operative course of discordant hepatic and renal xenotransplantation is complicated by a pulmonary injury. The aim of this study was to characterize the nature of this injury, as well as to determine whether endothelin-1 (ET-1) and inducible-nitric oxide synthase (iNOS) are present in this form of pulmonary injury. Dog-to-pig orthotopic liver and kidney xenografts were performed. Pulmonary artery pressures were monitored throughout all procedures. The lungs were stained with monoclonal antibodies for ET-1, endothelin converting enzyme-1, and iNOS. The lungs from pig recipients of hepatic or renal xenografts were compared to lungs from untreated pigs. Pulmonary artery pressures were elevated in recipients of liver xenografts when the suprahepatic caval cross clamp was placed and continued to rise to systolic levels following unclamping. The mean pulmonary artery pressures in recipients of renal and hepatic xenografts rose significantly following revascularization. Pathology in lungs from kidney and liver recipients was similar, showing congestion with peribronchial and septal edema, with diffuse adhesion of PMN to alveolar endothelium. ET-1, endothelin converting enzyme-1 (ECE-1), and iNOS staining was widespread and intense in alveolar and pulmonary arterial endothelium. Discordant xenotransplantation of livers and kidneys is associated with a significant early pulmonary injury that is associated with early PMN infiltration and expression of ET-I and iNOS.     

Function of dynamically stimulated endothelium and renin–angiotensin–aldosterone system in normotensive subjects with a family history of hypertension

Aim: Genetic influences on the acute stimulation of the renin–angiotensin–aldosterone system (RAAS) and on endothelial activation were studied by examining healthy blood donors with and without hypertensive parents. Methods: Healthy blood donors were assigned to two groups, according to the presence or absence of a parental history of hypertension. Plasma levels of renin, nitric oxide (NO) and plasminogen activator inhibitor 1 (PAI-1) were studied before and after acute alterations in renal perfusion induced by phlebotomy, and the two groups compared. During phlebotomy, 400–500 mL of blood was extracted from each subject, with that volume varying relative to each subject's body surface area (m²). Results: No statistically significant inter-group differences were observed between the baseline mean levels of plasma renin, NO or PAI-1. After phlebotomy, significant increases were detected in mean plasma renin activity (PRA) and NO levels and in PAI-1 activity (P < 0.001). However, the increases in mean PRA (P < 0.05) level and PAI-1 activity (P < 0.05) were more pronounced in those with hypertensive parents than those without; conversely, the increase in NO levels was more pronounced in the latter group. No statistically or clinically significant difference was found between the mean body mass indices of these two groups. Only two subjects were overweight, and none were obese; the remainder had weights that were normal. We found no significant correlation between body mass index and either NO or PAI-1 level. Conclusion: Post-phlebotomy, PRA and PAI-1 responses were more dramatic, but the NO response less in normotensive subjects having a parental history of hypertension, suggesting that these changes may represent familial, possibly genetic influences before overt hypertension occurs.     

Effects of endothelin-1 and endothelin-1-receptor blockade on renal function in humans.

BACKGROUND: In patients with renal or cardiac failure, renal function may be endangered by elevated plasma concentrations of the vasoconstrictor endothelin-1 (ET-1). To mimic effects of pathologically increased plasma ET-1, we gave intravenous ET-1 in healthy subjects and examined whether simultaneous infusion of the ETA-receptor antagonist VML 588 would prevent the effects of ET-1 on the kidney. METHODS: Nine healthy men received on four separate days intravenous infusion of ET-1 (2.5 ng/kg/min) superimposed on vehicle (saline) or on VML 588 infusion (0.05, 0.20 and 0.40 mg/kg/h) in randomized order to assess the effects on renal function and renal haemodynamics. RESULTS: At resting plasma ET-1, infusion of VML 588 alone had no significant effects on renal function. Infusion of ET-1 alone decreased glomerular filtration rate by 11% and this reduction was not reversed by co-infusion of VML 588. ET-1 reduced renal blood flow by 35% and VML 588 reduced this decrease by one-third, in a dose-independent fashion. ET-1 increased the filtration fraction by 34% and VML 588 reduced this increase dose-independently by one-half. ET-1 increased renal vascular resistance by 59% and VML 588 reduced this increase dose-independently by one-half. Finally, ET-1 decreased sodium excretion by 58% and VML 588 reduced this decrease dose-independently by two-thirds. CONCLUSIONS: ET-1-induced reductions in renal function were partially but not completely prevented in a dose-independent manner by the ETA-receptor antagonist VML 588.     

银杏叶提取物对野百合碱所致肺动脉高压保护作用的实验研究

目的：探讨银杏叶提取物对野百合碱所致肺动脉高压（PAH）的早期保护作用。方法：30只雄性 SD大鼠随机分为3组：对照组、PAH 模型组和治疗组,每组10只。PAH 模型组和治疗组大鼠采用脊背部皮下注射1%野百合碱60 mg/kg的方法复制PAH 模型,注射后第2天开始每日予2 ml 0.9%氯化钠注射液（PAH 模型组）或60 mg/kg银杏叶提取物（治疗组）灌胃;对照组脊背部皮下注射等量溶剂,注射后第2天开始每日予2 ml 0.9%氯化钠注射液灌胃。第22天采用颈外静脉右心导管法测定平均肺动脉压（mPAP）、右心室收缩压（RVSP）,测定右心室、左心室、室间隔的重量,计算右心室肥厚指数（RVHI）;采用 HE染色观察肺细小动脉组织结构情况,并计算直径50~150μm的肺小动脉血管管壁厚度占血管厚度百分比（WA%）和血管管壁面积与血管面积比值（WV%）;采用免疫组化方法观察内皮型一氧化氮合成酶（eNOS）及内皮素-1（ET-1）在大鼠肺组织中的表达情况。结果：PAH 模型组、治疗组的 mPAP、RVSP、RVHI、WA%、WV%与对照组比较均明显升高（P〈0.05）,治疗组的 mPAP、RVSP、WA%、WV%较 PAH 模型组均降低（P〈0.05）,而治疗组与 PAH 模型组的RVHI差异无显著性。免疫组化结果显示,3组 eNOS表达,对照组〉治疗组〉PAH 模型组;3组 ET-1的表达, PAH 模型组〉治疗组〉对照组。结论：银杏叶提取物通过抑制 ET-1的合成、减轻内皮细胞损伤、维持 eNOS的表达,达到减缓PAH 进展的作用。     

Vascular effects of poly-N-acetylglucosamine in isolated rat aortic rings.

BAACKGROUND: Poly-N-acetylglucosamine (p-GlcNAc) is a secretion of marine diatoms that is known to be useful in controlling bleeding. As a component of promoting hemostasis, p-GlcNAc is thought to exert vasoconstrictor effects in arteries. The present study was undertaken to determine whether p-GlcNAc induced a significant vasoconstrictor effect and, if so, what the mechanism of this effect might be. MATERIALS AND METHODS: We examined vascular effects of p-GlcNAc on isolated aortic rings obtained from Sprague-Dawley rats. The rings were suspended in organ baths and precontracted with U46619, a thromboxane A2 mimetic. RESULTS: p-GlcNAc produced a concentration-dependent vasoconstriction over the range of 14 to 100 microg/ml. At a concentration of 100 microg/ml, p-GlcNAc significantly contracted aortic rings by 133 +/- 20 mg of developed force (P < 0.01). Neither a deacetylated derivative of p-GlcNAc nor a structurally related macromolecule, chitin, contracted rat aortic rings, indicating a specificity for p-GlcNAc. The vasoconstriction to p-GlcNAc was totally abolished in deendothelialized rat aortic rings, suggesting that an endothelial component is essential to the vasoconstriction. Pretreatment with the endothelin ET(A) receptor antagonist, JKC-301 (0.5 and 1 microM), significantly diminished p-GlcNAc-induced vasoconstriction by 57 to 61% (P < 0.01). However, p-GlcNAc did not significantly diminish nitric oxide release from rat aortic endothelium. CONCLUSION: These results provide evidence that p-GlcNAc significantly contracts isolated rat aortic rings via an endothelium-dependent mechanism, partly via enhancement of endothelin-1 release from endothelial cells.     

Haemodynamic and renal effects of endothelin receptor antagonism in patients with chronic kidney disease.

BACKGROUND: Endothelin-1 (ET-1) has been implicated in the pathophysiology of chronic kidney disease (CKD) and ET receptor blockade has shown renoprotective effects in animals. We examined the haemodynamic and renal effects of an ET receptor antagonist, TAK-044, in patients with CKD. METHODS: Seven patients with CKD (mean arterial pressure 103 mmHg; mean plasma creatinine 3.5 mg/dl) received three 15 min intravenous infusions, each separated by at least 7 days, of either placebo or TAK-044 (100 or 750 mg) in a randomized, double blind crossover study. Systemic and renal haemodynamics, and plasma immunoreactive ET-1, big ET-1 and C-terminal fragment concentrations, were determined before and after the infusions of placebo and drugs. RESULTS: Compared with placebo, TAK-044 reduced mean arterial pressure (MAP) (100 mg: 7.4 +/- 1.9 mmHg, 750 mg: 8.4 +/- 2.3 mmHg, P < 0.01) and systemic vascular resistance index (100 mg: 650 +/- 140 dyne.s.cm(-5).m(-2), 750 mg: 829 +/- 141 dyne.s.cm(-5).m(-2), P < 0.01) at both doses. TAK-044 increased cardiac index and heart rate to a similar degree at both doses. With regards to renal haemodynamics, TAK-044 had no significant effect on the glomerular filtration rate at either dose but tended to increase renal plasma flow (100 mg: 9.6 +/- 5.0 ml/min, 750 mg: 25.3 +/- 19.5 ml/min) and decreased the effective filtration fraction (100 mg: 3.6 +/- 1.1%, 750 mg: 4.7 +/- 1.7%, P < 0.01), in a dose-dependent manner. TAK-044 had no significant effect on sodium or lithium clearance, or on fractional excretion of sodium and lithium. Plasma ET-1 concentrations rose more than two-fold after 750 mg TAK-044 while big ET-1 and C-terminal fragment concentrations were unchanged. CONCLUSIONS: These findings suggest an important role for ET-1 in controlling systemic and renal haemodynamics in patients with CKD. The antihypertensive and potentially renoprotective actions of ET receptor antagonists shown in this study may prove useful in slowing the progression of CKD. Clinical trials are now needed to address these key questions for CKD.