阿托伐他汀对自发性高血压大鼠血压、循环和心肌血管紧张素Ⅱ水平的影响

目的：观察阿托伐他汀对自发性高血压大鼠（SHR）血压、循环和心肌血管紧张素Ⅱ(Ang Ⅱ)水平的影响。 方法: 24只SHR随机分为4组（每组6只）：SHR对照组、阿托伐他汀50 mg组、阿托伐他汀10 mg组和缬沙坦组, 6只WKY大鼠作为正常血压对照组（WKY组）。给药前和给药后每两周测量大鼠尾动脉收缩压（SBP）。测定血清脂质及血浆和心肌血管紧张素Ⅱ（AngⅡ）水平。 结果: SHR各组SBP于给药前无显著差异（P>0.05），但均显著高于WKY组（P<0.01）；给药后第4、6周,阿托伐他汀50 mg组SBP明显低于SHR对照组（P<0.01）,10 mg组则不明显；缬沙坦组自给药后第2周，SBP进行性下降（P<0.01）。SHR对照组与WKY组血脂各项指标无显著差异（P>0.05）；阿托伐他汀50 mg组TC、TG及LDL-C水平明显低于SHR对照组（P<0.05，P<0.01），10mg组仅LDL-C水平明显下低于SHR对照组（P<0.05）。SHR对照组血浆AngⅡ浓度无明显差异，但心肌AngⅡ浓度明显高于WKY组（P<0.05）；给药6周后，阿托伐他汀各剂量组和缬沙坦组血浆AngⅡ浓度显著高于SHR对照组（均P<0.01），而心肌AngⅡ浓度在阿托伐他汀50 mg组和缬沙坦组明显低于SHR对照组（P<0.05）。 结论: 阿托伐他汀能降低SHR的血压，机制可能与降低心肌AngⅡ浓度含量有关。     

低温对大鼠血浆及不同脑区神经肽等活性物质含量变化的影响

目的:探讨低温对血浆及不同脑区精氨酸加压素 (AVP)、血管紧张素Ⅱ (AngⅡ)、亮氨酸-脑啡肽 (L-EK)、环磷酸腺苷 (cAMP)、Ca²⁺ 及Mg²⁺含量影响。方法:复制大鼠实验性低温模型,随机分组处理,实验结束时,取下丘脑、脑干及血样品,采用放射免疫法测定AVP、AngⅡ、L-EK、cAMP的含量,原子吸收法测定Ca²⁺ 及Mg²⁺含量。结果:实验组L-EK、cAMP、Ca²⁺ 及Mg²⁺值显著高于对照组 (P <0.01);实验Ⅰ组、Ⅲ组血浆AVP、AngⅡ值显著高于对照组 (P <0.01),Ⅱ组显著低于对照组 (P <0.01)。实验Ⅰ组、Ⅲ组下丘脑和脑干AVP、AngⅡ值显著低于对照组 (P<0.01),Ⅱ组显著高于对照组 (P <0.01)。结论:低温时,L-EK、AVP、AngⅡ、cAMP、Ca²⁺ 及Mg²⁺可能参与体温调节.     

血清TNF-α、血管紧张素Ⅱ在CHF患者血红蛋白水平变化中的作用及其与心室重构关系的研究

目的： 研究血清肿瘤坏死因子α（TNF-α）、血管紧张素Ⅱ(AngⅡ)在慢性心力衰竭(CHF)患者血红蛋白水平变化中的作用，探讨肾素-血管紧张素系统、炎症细胞因子、血红蛋白水平变化与心室重构的关系。方法: 对入选的121例CHF患者测定了血红蛋白、血清TNF-α和AngⅡ水平，超声心动图测量左室射血分数(LVEF)，评价心功能；计算左心室质量指数（LVMI）和室壁应力（MWS）；按血红蛋白水平将CHF分为贫血组和非贫血组，同时选择27例正常人作为对照组。结果: CHF患者Hb水平低于正常对照组，而血清TNF-α和AngⅡ水平以及MWS和LVMI高于对照组（P<0.01）；随着心功能恶化，Hb水平逐渐降低，而血清TNF-α和AngⅡ水平以及MWS和LVMI逐渐升高；CHF贫血组患者血清TNF-α和AngⅡ水平以及MWS和LVMI明显高于非贫血组患者(P<0.01)；随着Hb水平降低，CHF患者血清TNF-α和AngⅡ水平以及MWS和LVMI明显升高 (P<0.01)； CHF患者MWS和LVMI与Hb水平呈负相关，与TNF-α、AngⅡ水平呈正相关(P<0.01)。结论: CHF患者TNF-α和AngⅡ水平的升高参与了CHF贫血和心室重构发生发展的病理生理过程，而CHF患者贫血的出现使CHF心室重构加重。     

早期应用氨基胍对糖尿病大鼠循环及肾脏血管紧张素Ⅱ水平的影响

目的： 观察早期应用氨基胍对糖尿病大鼠循环及肾脏血管紧张素Ⅱ（AngⅡ）水平的影响,探讨其对糖尿病肾脏形态、功能的保护作用及潜在AGEs与AngⅡ之间的作用关系。方法: Wistar大鼠随机分组,诱导糖尿病模型后,立即给予糖尿病干预组氨基胍。第12周末检测尿白蛋白排泄率（UAER）、肌酐清除率(Ccr),半定量评分评估肾脏病理改变,放免法、免疫组织化学法分别检测血浆及肾脏AngⅡ水平。结果: 与糖尿病对照组相比,氨基胍干预组UAER及肾脏病理改变程度显著减轻(P<0.01),肾脏AngⅡ水平明显减少(P<0.01),血浆Ang Ⅱ水平增加（P<0.01）。结论: 早期应用氨基胍可能通过阻断AGEs生成从而显著减少肾内AngⅡ水平,抑制局部肾素-血管紧张素系统激活,这可能是氨基胍保护糖尿病大鼠肾脏形态和功能的重要原因之一;氨基胍干预后糖尿病大鼠血浆AngⅡ水平升高可能与局部AngⅡ水平下降后机体的代偿反应有关,具体机制尚需进一步实验证实。     

抑制一氧化氮合酶对大鼠主动脉血管紧张素Ⅱ受体的影响

目的:本文应用NO合酶(NOS)竞争性抑制剂左旋硝基精氨酸(L-NNA)诱导大鼠高血压,观察对主动脉血管紧张素Ⅱ(AngⅡ)和AngⅡ受体的影响。方法:采用腹腔注射L-NNA复制大鼠高血压模型,分别用放射免疫法测定主动脉AngⅡ、放射配基结合法测定主动脉组织AngⅡ受体和Griess法测定血浆NOx含量。结果:L-NNA使大鼠血压明显高于对照组(+142%,P＜0.01),4周组心系数高128%(P＜0.01),血浆NOx水平低于对照组48%,血浆AngⅡ水平无明显差异;血管组织AngⅡ含量4周组显著高612%(P＜0.01),且4周组[¹²⁵I]-AngⅡ最大结合能力(Bmax)高6倍(P＜0.01),亲和力(Kd)高1倍(P＜0.01)。结论:抑制NOS诱导高血压主要是通过局部组织肾素-血管紧张素系统(RAS)发挥作用的,长期慢性抑制NOS可使血管组织AngⅡ水平升高并导致血管AngⅡ受体上调,此结果为"NOS抑制诱发AngⅡ依赖型高血压"假说提供新的依据。     

肾素-血管紧张素-醛固酮系统在原发性高血压病中的表达

目的:探讨血浆肾素-血管紧张素系统与原发性高血压病的关系。方法:采用放射免疫分析卧位血浆肾素活性(PRA),卧位血管紧张素Ⅱ(AngⅡ)浓度及卧立位醛固酮(ALD)浓度。使用病例-正常对照研究方案,筛选100例原发性高血压患者和我院35例血压正常者为对照组。结果:原发性高血压患者血浆卧位PRA低于正常对照组(P<0.05),而卧、立位ALD浓度及卧位AngⅡ浓度均高于正常对照组(P<0.05)。根据高血压病1级、2级、3级分组,卧位血浆PRA呈阶梯型下降(P<0.05);而卧、立位ALD浓度及卧位AngⅡ浓度则呈阶梯型上升(P<0.05)。结论:肾素-血管紧张素-醛固酮系统与原发性高血压病的病因关系密切,血浆PRA水平、AngⅡ及卧、立位ALD浓度可能成为原发性高血压病分级和疗效的有效指标之一;降低原发性高血压患者AngⅡ及ALD浓度是治疗高血压病的关键。     

氯沙坦逆转高血压大鼠阻力血管重塑的实验研究

目的:探讨氯沙坦对自发性高血压大鼠(SHR)阻力血管重塑的影响。方法:将雄性SHR20只随机分为氯沙坦治疗组和SHR对照组。另选同系雄性WKY大鼠10只作为正常对照组。治疗组给予氯沙坦30mg/kg/天,溶于饮水灌胃治疗17周。颈动脉插管,心电血流动力学监护仪测定动脉收缩压,应用计算机图像分析,计算血管壁腔面积比,用光镜和透射电镜观察SHR肠系膜动脉三级分支结构的变化;血浆放免法测肾素活性和血管紧张素Ⅱ(AngⅡ)含量。结果:氯沙坦治疗组的血管壁腔面积比与SHR对照组相比有所降低(P<0.05),但与WKY相比有所升高(P<0.05);血浆肾素活性在WKY组和SHR对照组之间无明显差异(P>0.05),治疗组肾素活性高于SHR对照组(P<0.05);治疗组的AngⅡ水平高于SHR对照组(P<0.01)。结论:氯沙坦具有逆转SHR血管重塑的作用。     

卡托普利对压力负荷增加大鼠血浆血管紧张素Ⅱ、心钠素及醛固酮水平的影响

目的:观察卡托普利对压力负荷增加大鼠血浆血管紧张素Ⅱ(AngⅡ)、心钠素(ANP)及醛固酮(ALD)水平的影响,探讨卡托普利对左室重构的干预机制。方法:清洁级雄性SD大鼠36只随机分为3组:假手术组、模型组、卡托普利组,每组12只。采用放射免疫分析法检测血浆AngⅡ、ANP及ALD水平,观察左室重量指数(LV-MI)变化。结果:模型组LVMI明显高于假手术组(P0.01);血浆AngⅡ、ANP、ALD水平较假手术组显著升高(P0.01)。与模型组比较,卡托普利组血浆AngⅡ、ANP、ALD水平及LVMI均明显下降(P0.01,P0.05)。结论:压力负荷增加所致左室重构的作用可能与血浆AngⅡ、ANP及ALD水平升高有关。卡托普利可降低压力负荷增加大鼠血浆AngⅡ、ANP及ALD水平;延缓或对抗左室重构的发生发展。     

肾性高血压大鼠血浆ET、CGRP、AngⅡ水平变化及缬沙坦、贝那普利干预的影响

目的:研究肾性高血压大鼠血浆内皮素(ET)、降钙素基因相关肽(CGRP)、血管紧张素Ⅱ(AngⅡ)等血管活性物质的变化及降压药物缬沙坦、贝那普利干预对收缩压和ET、CGRP、AngⅡ的影响。方法:采用两肾一夹方法复制肾性高血压大鼠模型,成模大鼠随机分为缬沙坦组(30mg/kg/天,n=8)、贝那普利组(10mg/kg/天,n=8)、肾性高血压模型组(n=8);假造模大鼠作为假手术组(n=10),前两组以缬沙坦和贝那普利溶液、后两组以等量生理盐水每日灌胃。分别于术前及术后每周末测定各组大鼠收缩压变化,并在灌药治疗8周后用放免法测定各组血浆ET、CGRP、AngⅡ含量变化。结果:两肾一夹术后4周可形成稳定肾性高血压大鼠模型。缬沙坦组、贝那普利组大鼠经灌胃治疗8周后血压明显下降(P<0.01)。肾性高血压模型组ET、CGRP、AngⅡ血浆浓度均高于假手术组(P<0.05或P<0.01);缬沙坦组、贝那普利组CGRP浓度高于肾性高血压模型组(P<0.05),贝那普利组AngⅡ浓度低于肾性高血压模型组和缬沙坦组(P<0.05);肾性高血压模型组血浆ET与AngⅡ浓度呈正相关(r=0.62,P<0.05)。结论:肾性高血压大鼠血浆ET、CGRP、AngⅡ浓度增高,缬沙坦、贝那普利可能通过调节血管活性物质水平而降低收缩压。     

HO通过减少ROS生成抑制AngⅡ的致血管平滑肌细胞增殖肥大

目的:观察血红素加氧酶（HO）在AngⅡ致血管平滑肌细胞（VSMCs）增殖和肥大中的作用并探讨其可能机制。方法:（1)免疫印迹法测定平滑肌细胞HO-1蛋白表达水平;（2）β-液体闪烁记数仪测定［3H］-TdR和［3H］-亮氨酸掺入量;（3)乙酰乙酸双氯荧光素（DCFH-DA）法测定平滑肌细胞内活性氧（ROS）水平。结果:（1) Hemin组HO-1蛋白表达水平与对照组和AngⅡ组相比均明显升高（P<0.01）。（2）AngⅡ使血管平滑肌细胞［3H］-TdR和［3H］-亮氨酸掺入量较对照组分别升高20.7％和18.0％（P<0.01）,而给予HO底物Hemin则抑制了［3H］-TdR和［3H］-亮氨酸掺入量的增加, 给予HO的抑制剂ZnPPIX则可以促进AngⅡ所致的［3H］-TdR、［3H］-亮氨酸掺入量的增加。(3) AngⅡ组ROS水平明显高于对照组（P<0.01）;Hemin组ROS水平较AngⅡ组降低了62.7％,而ZnPPIX组高于AngⅡ组39.5％。结论:HO可抑制AngⅡ所导致的VSMCs的增殖和肥大,其机制可能与减少细胞内ROS生成有关。     

The role of the brain renin–angiotensin system in hypertension: Implications for new treatment

Hypertension affects 26% of adults and is in constant progress related to increased incidence of obesity and diabetes. One-third of hypertensive patients may be successfully treated with one antihypertensive agent, one-third may require two agents and in the remaining patients will need three agents for effective blood pressure (BP) control. The development of new classes of antihypertensive agents with different mechanisms of action therefore remains an important goal. Brain renin–angiotensin system (RAS) hyperactivity has been implicated in hypertension development and maintenance in several types of experimental and genetic hypertension animal models. Among the main bioactive peptides of the brain RAS, angiotensin (Ang) II and Ang III have similar affinities for type 1 (AT1) and type 2 (AT2) Ang II receptors. Following intracerebroventricular (i.c.v.) injection, Ang II and Ang III similarly increase arginine–vasopressin (AVP) release and BP. Blocking the brain RAS may be advantageous as it simultaneously (1) decreases sympathetic tone and consequently vascular resistance, (2) decreases AVP release, reducing blood volume and vascular resistance and (3) blocks angiotensin-induced baroreflex inhibition, decreasing both vascular resistance and cardiac output. However, as Ang II is converted to Ang III in vivo, the exact nature of the active peptide is not precisely determined. We summarize here the main findings identifying AngIII as one of the major effector peptides of the brain RAS in the control of AVP release and BP. Brain AngIII exerts a tonic stimulatory effect on BP in hypertensive rats, identifying brain aminopeptidase A (APA), the enzyme generating brain Ang III, as a potentially candidate target for hypertension treatment. This has led to the development of potent orally active APA inhibitors, such as RB150 — the prototype of a new class of centrally acting antihypertensive agents.     

Abnormal vasopressin and aldosterone response to furosemide in essential hypertension

Plasma concentrations of arginine vasopressin (AVP), angiotensin II (AII), aldosterone (Aldo), urinary output (V), osmolar clearance (Cosm), free water clearance (CH2O), fractional excretions of sodium (FENa) and potassium (FEK), urinary sodium excretion rate (U-Na) and serum potassium (S-K) were determined in 9 patients with essential hypertension (group I) and 13 normotensive healthy control subjects (group II) before and three times during the first 4 hours after an intravenous injection of 40 mg of furosemide. AVP, AII, Aldo, V, Cosm, FENa, FEK and U-Na increased in both groups. However, the elevation in AVP was significantly more pronounced and the rate of increase in Aldo was significantly slower in group I than in group II. There were no significant differences in AII, V, Cosm, CH2O, FENa, FEK and U-Na between the groups. S-K was significantly reduced only in group I. AVP and AII were not significantly correlated to each other or to blood pressure. It is suggested that the responsiveness of the renal tubules to AVP is reduced in essential hypertension and that the larger increase in AVP might be a compensatory phenomenon. The slower increase in Aldo in essential hypertension could be attributed to the reduction in S-K.     

Expansion of extracellular volume in early polycystic kidney disease

Blood volume (BV), extracellular volume (ECV), blood pressure (BP), creatinine clearance (CCr), plasma levels of angiotensin II (AII), aldosterone (Aldo) and arginine vasopressin (AVP), and serum osmolality (Sosm) were determined in 18 patients with adult polycystic kidney disease, 8 normotensive (group I), 10 hypertensive (group II), and in 11 control subjects (group III). ECV but not BV was increased in group I compared with group III, whereas BV and ECV did not differ significantly between groups II and III. In group II, Aldo and AVP were increased and AII tended to be increased, while in group I the hormone levels did not differ significantly from those in group III. Sosm did not differ significantly between the groups. In the combined patient group, CCr correlated positively with BV and ECV and negatively with BP. In the patients, AII and AVP were positively correlated with BP but not with CCr. The results suggest that both the renin-angiotensin system and AVP might be involved in the BP elevation, whereas expansion of ECV can be found without an increase in BP.     

Urinary excretion of angiotensin I, II, arginine vasopressin and oxytocin in patients with anaphylactoid reactions

Human urine samples, purified on octadecasilyl-silica cartridges, contained immunoreactive angiotensin I, II, arginine vasopressin and oxytocin. The daily excretion of these peptides in healthy volunteers was 190.00 +/- 38.43 (n = 12), 17.48 +/- 3.09 (n = 12), 63.43 +/- 14.84 (n = 8) and 13.52 +/- 1.42 (n = 7) pmol/24 hr, respectively (mean +/- s.e.m.). Patients with a history of anaphylactoid reactions to drugs or food additives showed clinical symptoms such as urticaria, flush, nausea, dizziness and hypotension after oral provocation with cyanocobalamine, propyphenazone, acetylsalicylic acid and sodium benzoate. In five of the seven patients, angiotensin I and II were increased several fold in the urine fractions after symptoms were reported. The average increase in the urine concentration of both peptides was fourfold and 5.5-fold. In three out of five patients, the mean excretion of arginine vasopressin and oxytocin immunoreactive material was also elevated by a factor of 5.7 and 4.4, respectively. Oral provocation with a placebo failed to elicit anaphylactoid symptoms or an increase in the urine levels of angiotensin I or angiotensin II. Angiotensin I and angiotensin II-like immunoreactivity could be characterized on HPLC as Ile5-angiotensin I, Ile5-angiotensin II and angiotensin II metabolites. HPLC characterization of immunoreactive arginine vasopressin and oxytocin in two different gradient systems showed retention times different than the retention times of the corresponding synthetic standard peptides indicating that both peptides are not authentic AVP and OXT. These results suggest that angiotensin I and angiotensin II may be involved in the clinical events observed during some forms of anaphylactoid reactions.     

急性创伤性脑损伤患者初期血清NSE含量及判断限值的探讨

目的：探讨血清NSE的含量在脑损伤的诊断和评估伤情及预后早期判断中的临床意义,建立其判断限值。方法：采用发光免疫法,分析了79例急性脑损伤患者初期血清NSE的含量,并与98例正常人组及86例非神经系统疾病患者的检测结果作比较。对不同程度、不同预后的脑损伤患者血清NSE含量的差别,进行显著性检验,并对GCS评分与NSE间的关系作相关分析,通过对不同判断值的临床可用性能评价确定脑损伤患者血清NSE的判断限值。结果：急性创伤性脑损伤组血清NSE含量显著高于正常人组及非神经系统疾病组（P〈0.001）,急性重型脑损伤组患者血清NSE的浓度〉中型组〉轻型组（P〈0.01,〈0.05）,相关分析显示,急性脑损伤患者初期血清NSE的浓度与GCS评分呈负相关（r=-0.8921,P〈0.01）。并发现脑损伤初期血清NSE浓度〈30ng/ml组和（30～60）ng/ml组及≥60ng/ml组的急性创伤性脑损伤患者的预后良好率分别为97.4%和75%及18.8%,残废率分别为2.6%和20.8%及50.0%,死亡及植物生存率分别为0%和2.6%及31.2%,三组间预后的构成比有显著性差异（P〈0.05,〈0.01）。临床可用性能评价结果显示,判断值提高至22.0ng/ml时,准确度和可用度均名列第一,其诊断试验的特异性和敏感性分别达88.4%和62%。结论：血清NSE含量测定不仅是脑损伤诊断和伤情评估的一项量化指标,而且有望成为早期判断预后的手段之一。脑外伤后血清NSE浓度≥22ng/ml应首先考虑脑损伤的存在。     

Hormonal regulation of renomedullary hyaluronan

Aim: Hyaluronan (HA) is involved in renomedullary water handling through its water‐binding capacity. This study addressed the effect of hormones involved in regulating fluid‐electrolyte homeostasis on renomedullary HA content in vivo and in vitro. Methods: The kidneys from rats treated with l ‐NAME, indomethacin, vasopressin (AVP) or methylprednisolone (MP) during euvolaemia or water loading were analysed for HA by RIA, ELISA and histochemical staining. HA was measured in renomedullary interstitial cells treated with AVP, angiotensin II (Ang II) or a combination of AVP and Ang II. Results: Baseline renal cortical and medullary HA content was unaffected by 2 h of intravenous treatment with l ‐NAME (NOS inhibitor) or indomethacin (cyclo‐oxygenase inhibitor), whereas AVP reduced medullary HA by 33%. During 2 h of acute water loading, diuresis was accompanied by an increase in renomedullary HA (+45%), but cortical HA was unaffected. In both l ‐NAME‐ and indomethacin‐treated animals, the water loading‐induced increase in renomedullary HA was absent, indicating involvement of NO and prostaglandins. After 7 days of MP treatment, medullary HA was reduced by 40%, but the water loading‐induced elevation in HA remained. In cultured renomedullary interstitial cells, AVP reduced the HA content in the supernatant by 63%, and simultaneous treatment with Ang II reduced the HA content even further (95%). Conclusion: AVP reduces HA content, and NO and prostaglandins are needed for the increase in HA during water loading.     

Higher serum prolyl endopeptidase activity in patients with post-traumatic stress disorder.

BACKGROUND: It is reported that psychiatric disorders, such as depression and schizophrenia, are associated with changes in serum activity of prolyl endopeptidase (EC 3.4.21.26), a cytosolic endopeptidase, which cleaves peptide bonds on the carboxylside of proline in proteins of relatively small molecular mass. AIMS AND METHODS: The aims of the present study were to examine serum PEP activity in patients with post-traumatic stress disorder (PTSD) versus healthy volunteers. PEP activity has been determined by a fluorimetric assay. RESULTS: Serum PEP activity was significantly higher in patients with PTSD than in normal volunteers. Serum PEP activity was significantly higher in patients with PTSD and concurrent major depression than in patients with PTSD without major depression. In PTSD patients, there were no significant correlations between serum PEP activity and severity of PTSD symptoms. CONCLUSIONS: The results show that PTSD and, in particular, PTSD with concurrent major depression is associated with increased activity of PEP. RELEVANCE: these results may be of importance for the (i) neuroendocrine pathophysiology of PTSD since PEP degrades neuropeptides, such as arginine vasopressin (AVP) and thyrotropin releasing hormone (TRH); and (ii) etiology of PTSD, since PEP degrades behaviorally active neuropeptides, such as AVP, TRH, oxytocin, neurotensin and substance P, which play a key role in positive reinforcement, social interactions, emotions and stress responsivity.     

Intracerebroventricular injection of brain natriuretic peptide inhibits vasopressin secretion in conscious rats

The effect of intracerebroventricular (i.c.v.) injection of brain natriuretic peptide (BNP), a novel peptide purified from the porcine brain, on arginine vasopressin (AVP) secretion was studied in conscious, unrestrained rats and was compared with that of atrial natriuretic polypeptide (ANP). I.c.v. administration of BNP (0.01, 0.1 or 1 nmol) significantly inhibited basal AVP secretion and the effect of BNP was comparable to that of ANP. The AVP secretion induced by i.c.v. injection of angiotensin II (0.1 nmol) was significantly suppressed by the pretreatment with BNP (0.1 or 1 nmol). These results suggest that BNP is involved in the central control of AVP secretion either alone or in combination with brain ANP.     

Central nitric oxide blocks vasopressin, oxytocin and atrial natriuretic peptide release and antidiuretic and natriuretic responses induced by central angiotensin II in conscious rats

The presence of nitric oxide synthase (NOS), the enzyme that catalyses the formation of nitric oxide (NO), in the circumventricular organs and magnocellular neurones suggests an important role of NO in the modulation of vasopressin (AVP) and oxytocin (OT) release. Intracerebroventricular (I.C.V.) injection of angiotensin II (Ang II) stimulates the release of AVP, OT and atrial natriuretic peptide (ANP), with the resultant antidiuretic and natriuretic effects. This study investigated the interaction between nitrergic and angiotensinergic pathways on the release of AVP, OT and ANP and on urinary volume and sodium excretion in water-loaded rats. Unanaesthetized, freely moving, male Wistar rats received two water loads followed by an injection into the lateral ventricle of an inhibitor of NOS (L-NAME), a NO donor [3-morpholinylsydnoneimine chloride (SIN-1) or S-nitroso-N-acetyl penicillamine (SNAP)] or vehicle (isotonic saline) and, 20 min after, they received a second I.C.V. injection of Ang II or vehicle. Injections of L-NAME or Ang II produced an increase in plasma levels of AVP, OT and ANP, a reduction in urinary volume and an increase in sodium excretion. Pretreatment with L-NAME enhanced the Ang II-induced increase in AVP, OT and ANP release, as well as the antidiuresis and natriuresis. Injection of SIN-1 or SNAP did not modify hormonal plasma levels and urinary parameters. In contrast SNAP blocked the AVP, OT and ANP release, as well as antidiuretic and natriuretic responses induced by ANG-II. Thus, the central nitrergic system can act to inhibit AVP, OT and ANP secretion and the antidiuretic and natriuretic effects in response to Ang II.     

Role of calcium in osmotic and nonosmotic release of vasopressin from rat organ culture

In the present study the role of calcium (Ca) in the stimulation of arginine vasopressin (AVP) release from the cultured rat hypothalamoneurohypophyseal complex (HNC) was examined in response to three different stimuli, 56 mM potassium chloride, an increase in medium osmolality from 290 to 310 mosmol/kg H2O, or 1 X 10(-6) M angiotensin II (ANG II). With all three stimuli AVP release from rat HNC explants was enhanced by increasing Ca concentration in the medium from 0 to 1.8 mM Ca. However, high concentrations of Ca (8 mM) inhibited the response of AVP release to either hyperosmolality or angiotensin II. Chemically dissimilar blockers of cellular Ca uptake, verapamil (5.2 X 10(-6) or 5.2 X 10(-5) M) or nifedipine (5.8 X 10(-6) or 5.8 X 10(-5) M), completely abolished AVP release from rat HNC explants in response to the three different stimuli in 1.8 mM Ca. In a normal concentration of medium Ca (1.8 mM) a Ca ionophore, A23187 (3.8 X 10(-5) M), significantly enhanced the osmotic and nonosmotic (ANG II-stimulated) release of AVP from rat HNC explants compared with controls without Ca ionophore. This effect of Ca ionophore to enhance AVP release was more evident in a lower Ca medium (0.9 mM Ca in the hyperosmolality study and 0.3 mM Ca in the ANG II study). These results therefore indicate that cellular Ca uptake is an important modulator of osmotic and nonosmotic AVP release from the intact rat hypothalamoneurohypophyseal system. The influence of extracellular Ca on the osmotic and nonosmotic release of AVP is also demonstrated.