肾上腺髓质素的和压作用及其在组织中分布的观察

本实验用电生理和免疫组化方法观察了肾上腺髓质素（ａｄｒｅｎｏｍｅｄｕｌｉｎ，ＡＭ）对正常和高血压大鼠血压的影响和对主动脉环张力的作用以及ＡＭ在一些组织中的分布特点。结果显示ＡＭ对高血压大鼠的降压幅度远大于正常鼠；对主动脉环张力的降低作用具有剂量依赖性和内皮依赖性；ＡＭ免疫组化反应除在嗜铬细胞瘤和肾髓质细胞内呈阳性反应外，在肺、肾和心肌组织内部都显示出不同程度的阳性。提示ＡＭ在机体血压循环调节中具有     

侧脑室注射肾上腺髓质素对实验性高血压大鼠血压和心率的影响

肾上腺髓质素(ａｂｒｅｎｏｍｅｄｕｌｌｉｎ,ＡＭ)最先是从肾上腺髓质嗜铬细胞瘤组织中发现的含52个氨基酸的生物活性多肽。ＡＭ广泛分布于肾上腺髓质、肺、肾、小肠、心脏、血管等外周组织和血液中。静脉注射ＡＭ可引起正常大鼠强而持久的降低血压作用。中枢途径的ＡＭ对高血压时心血管活动的影响尚未见报道,本实验旨在观察侧脑室注射ＡＭ对腹主动脉狭窄高盐摄入型高血压大鼠血压和心率的影响,并探讨其可能的中枢作用机制。1　材料和方法动物分组:本实验制成功高血压大鼠40只,假手术大鼠6只。在高血压大鼠中随机抽取9只测血压,取心,证明已…     

一种新发现的降压活性多肽—肾上腺髓质素（adrenomedullin）

肾上腺髓质素是最近发现的一种新的活性多肽,它广泛分布于机体多种组织中,具有扩张血管、降低血压、抑制内皮素和血管紧张素Ⅱ释放等作用。该活性多肽在正常机体血压调控及高血压发病中的作用正在研究中。     

肾上腺髓质素（13—52）降压机制的探讨

本工作在整体和离体大鼠模型上观察肾上腺髓质素（１３－５２）［ＡｄＭ（１３－５２）］的降压机制,发现ＡｄＭ（１３－５２）的降压作用可被一氧化氮合酶（ＮＯＳ）竞争性拮抗剂Ｌ－Ｎ－硝基－精氨酸？（ＬＮＮＡ）部分抑制;ＡｄＭ１３－５２）的舒血管作用依赖于血管内皮并可被ＬＮＮＡ抑制,且具有剂量效应,ＬＮＮＡ这种效应可被Ｌ－精氨酸（ＬＡｒｇ）逆转;用亚甲蓝（ＭＢ）阻断血管内的环－磷酸鸟苷酸（ｘＧＭＰ）,则导致     

肾上腺髓质素的分子特征及生物学功能

1993年日本学者Ｋｉｔａｍｕｒａ等首次从人的嗜铬细胞瘤(ｐｈｅｏｃｈｒｏｍｏｃｙｔｏｍａ,ＰＣ)组织中分离出一种新的活性多肽,它具有舒张体循环和肺循环的血管、明显降低血压的作用,称为肾上腺髓质素(ａｄｒｅｎｏｍｅｄｕｌｌｉｎ,ＡＤＭ)。ＡＤＭ广泛分布于机体多种组织如肾上腺髓质、肺、肾、脾、小肠、心肌、大脑皮质中,其中尤以肾上腺髓质含量最高,约为150±24ｐｍｏｌ/ｇ湿组织。血浆中ＡＤＭ的浓度约为收稿日期:19991228作者简介:朱赓伯(1934—),男,教授。9±5.4ｆｍｏｌ/Ｌ,它主要来自肺和血管内皮细胞。目前认为ＡＤＭ是一种参…     

促肾上腺皮质激素引起大鼠肾上腺c—fos原癌基因表达的免疫…

采用冰冻切片免疫组化法观察了注射促肾上腺皮质激素（ＡＣＴＨ,７５Ｕ／ｋｇ）,胰岛素及正常对照大鼠中肾上腺务部分ｃ－ｆｏｓ原癌基因表达产物Ｆｏｓ蛋白的出现和分布特点。结果表明注射ＡＣＴＨ后９０ｍｉｎ,大鼠肾上腺皮质网状带出现Ｆｏｓ蛋白染色阳性细胞,阳性染色物集中于细胞核,肾上腺皮质束状带仅见少数Ｆｏｓ蛋白染色阳性细胞,肾上腺髓质则未见Ｆｏｓ蛋白染色阳性细胞。与注射ＡＣＴＨ相反,注射胰岛素引起肾上腺髓     

肾上腺髓质切除对慢性间歇性缺氧大鼠的血管重塑作用

摘要 目的：探究肾上腺髓质切除对慢性间歇性缺氧（CIH）大鼠的血管重塑作用。方法：将32只大鼠随机分为慢性间歇性空气（CIA）假手术组、CIA手术组、CIH假手术组、CIH手术组。制备CIH模型，手术组在缺氧前行肾上腺髓质切除术，假手术组行相同操作但不切除肾上腺髓质。测量尾动脉血压；ELISA法检测血清肾上腺素（E）、去甲肾上腺素（NE）含量；HE、Masson染色和荧光显微镜观察胸主动脉形态，计算胸主动脉中膜厚度、胶原容积分数和弹性纤维紊乱断裂比例；IHC观察胸主动脉α-平滑肌肌动蛋白（α-SMA）表达；TUNEL观察胸主动脉细胞凋亡率；WB检测胸主动脉天冬氨酸半胱氨酸酶-3（Caspase-3）蛋白表达。结果：与CIA假手术组比较，CIH假手术组E、NE、尾动脉收缩压、舒张压、胸主动脉中膜厚度、胶原容积分数、弹性纤维紊乱断裂比例、α-SMA水平、细胞凋亡率、Caspase-3表达升高（P＜0.05）；与CIH假手术组比较，CIH手术组E、NE、尾动脉收缩压、舒张压、胸主动脉中膜厚度、胶原容积分数、弹性纤维紊乱断裂比例、α-SMA水平、细胞凋亡率、Caspase-3表达降低（P＜0.05）。结论：切除肾上腺髓质可改善由慢性间歇性缺氧引起的大鼠胸主动脉重塑。     

肾上腺髓质素（13－52）降压机制的探讨

本工作在整体和离体大鼠模型上观察研究了肾上腺髓质素（１３－５２）［ＡｄＭ（１３－５２）］的降压机制,发现ＡｄＭ（１３－５２）的降压作用可被一氧化氮合酶（ＮＯＳ）的竟争性桔抗剂Ｌ－ＮＧ－硝基－精氨酸（ＬＮＮＡ）部分抑制;ＡｄＭ（１３－５２）的舒血管作用依赖于血管内皮并可被ＬＮＮＡ抑制,且具有剂量效应关系,ＬＮＮＡ的这种效应可被Ｌ－精氨酸（Ｌ－Ａｒｇ）逆转;用亚甲蓝（ＭＢ）阻断血管内的环－磷酸鸟苷酸（ｃＧＭＰ）,则导致ＡｄＭ（１３－５２）的舒血管作用消失;放免测定显示ＬＮＮＡ可以降低血管内ｃＧＭＰ含量,而ＡｄＭ（１３－５２）则使后者含量增加,这一现象在ＡｄＭ（１３－５２）与ＬＮＮＡ合用时消失。实验结果提示,ＡｄＭ（１３－５２）的舒血管降血压效应与ＮＯ有关,可能是通过ＮＯ介导的。     

肾上腺髓质素受体及其信号转导

肾上腺髓质素（Ａｄｍ）是新近发现的一种生物活性多肽,在体内有着广泛的分布,参与机体多种生理功能的调节。Ａｄｍ可与两种受体结合：ＣＧＲＰ受体和Ａｄｍ特异受体。Ａｄｍ与体结合后,通过ｃＡＭＰ－ＰＫＡ等信号转导通路发挥舒长血管、降低血压、利尿利钠和抑制细胞增殖等作用。     

大鼠肾上腺髓质儿茶酚胺分泌的在体伏安法测定

应用碳纤微电极直接测定大鼠肾上腺髓质中儿茶酚胺浓度的在体伏安法。首次报道了大鼠肾上腺髓质中儿茶酚胺的基础浓度为０．１－０．５μｍｏｌ／Ｌ,缺血时髓质中儿茶酚胺的浓度显著增加,严重缺血时可达到５－３０μｍｏｌ／Ｌ。肾上腺髓质能自发分泌儿茶酚胺,缺血时自发分泌儿茶酚胺的幅度和频率都大大增加,提示缺血对大鼠是一种强烈的应激,测定结果还表明,乙酰胆碱能剂量依赖性地刺激肾上腺髓质嗜铬细胞分泌儿茶酚胺。     

Stimulation of aortic tissue calcium uptake by an extract of spontaneously hypertensive rat erythrocytes possessing hypertensive properties

In earlier reports we have described the isolation of a fraction from the erythrocytes of spontaneously hypertensive rats that produced hypertension when administered to normotensive rats. In addition, it was found that the fraction stimulated the uptake of "lanthanum-resistant" calcium by aortic rings excised from normotensive rats. In these studies we have found that the fraction causes a greater increase in the in vitro uptake of calcium by aortic tissue than that produced by depolarization of the tissue with high K+ or the receptor-mediated influx of calcium induced with norepinephrine. The hypertensive fraction appeared to be more effective in promoting increased calcium uptake in rabbit than in rat aortic tissue, suggesting that significant differences in tissue sensitivity to the active compound(s) may exist between species. In addition, we obtained evidence indicating that the tissue sensitivity to the action of the hypertensive fraction was greater in aortae from spontaneously hypertensive rats than from those of normotensive animals. Attempts to block the action of the hypertensive fraction with verapamil, nifedipine, and sodium nitroprusside had no significant effect on the elevation in tissue calcium. It was found, however, that the action of the hypertensive fraction was temperature dependent with reduced activity at lower temperatures. The data suggest that a compound(s) is present in the erythrocytes of rats that may have a marked effect on vascular tissue metabolism of calcium.     

Bay K 8644-like contractile effects of a peptide isolated from spontaneously hypertensive rats

The in vitro contractile effect of a peptide recently isolated from the blood of spontaneously hypertensive rats was assessed on rat aortic rings. Preincubation of aortic rings with the peptide had no effect on resting tension but significantly enhanced K+ or norepinephrine-induced contractile responses. Contractile effects were abolished by removal of extracellular calcium or by additions of the calcium channel antagonists, verapamil and nifedipine. The antagonism of peptide enhancement of contraction by verapamil was noncompetitive, whereas nifedipine blockade was competitive in nature. Moreover, preincubation of aortic rings with the peptide attenuated the contractile response to Bay K 8644, a newly described synthetic calcium channel agonist. We suggest that this peptide has similar effects to Bay K 8644 and may act as an endogenous modulator of voltage-dependent calcium channels.     

Nitric oxide in cyclosporine A-induced hypertension: endothelin receptors gene expression.

Cyclosporine A (CsA) is an immunosuppressive agent, which also causes hypertension. The effect of CsA on vascular responses was determined in spontaneously hypertensive rats and isolated rat aortic rings. Male rats weighing 250-300 g were given either CsA (25 mg/kg/day) in olive oil or vehicle by i.p. injection for 7 days. CsA administration produced a 27% increase (P < 0.001) in mean arterial pressure (MAP) which reached a plateau after 3 days. Conversely, the level of nitrate/nitrite, metabolites of nitric oxide (NO), decreased by 44% (P < 0.001) in the urine. In the presence of endothelin (ET) 10(-9) M, thoracic aortic rings from rats treated with olive oil, L-Arginine (L-Arg) or L-Arg+CsA showed a 100% increase (P < 0.001) in tension compared to the aortic rings from rats treated with CsA alone; aortic rings from rats treated with CsA alone did not respond to ET. The effects of CsA were reversed in both in vivo and in vitro by pretreatment with L-Arg (10 mg/kg/day ip), the precursor of NO. There were no changes in MAP and tension in rats treated with L-Arg alone. Possible explanation for lack of response to ET of aortic rings from CsA treated rats may be that CsA affected ET signalling pathway; ET receptors mRNA (messenger ribonucleic acid) gene expression was inhibited in aortic rings of rats treated with CsA. In summary, CsA inhibits endothelial NO formation, with resulting increases in MAP, and this inhibition can be overcome by parenteral administration of L-Arg.     

l-Arginine attenuates cardiovascular impairment in DOCA-salt hypertensive rats

Nitric oxide (NO) is essential for normal function of the cardiovascular system. This study has determined whether chronic administration of l-arginine, the biological precursor of NO, attenuates the development of structural and functional changes in hearts and blood vessels of deoxycorticosterone acetate (DOCA)-salt hypertensive rats. Uninephrectomized rats treated with DOCA (25 mg every 4th day sc) and 1% NaCl in the drinking water for 4 wk were treated with l-arginine (5% in food, 3.4 +/- 0.3 g x kg body wt(-1) x day(-1)). Changes in cardiovascular structure and function were determined by echocardiography, microelectrode studies, histology, and studies in isolated hearts and thoracic aortic rings. DOCA-salt hypertensive rats developed hypertension, left ventricular hypertrophy with increased left ventricular wall thickness and decreased ventricular internal diameter, increased inflammatory cell infiltration, increased ventricular interstitial and perivascular collagen deposition, increased passive diastolic stiffness, prolonged action potential duration, increased oxidative stress, and inability to increase purine efflux in response to an increased workload. l-Arginine markedly attenuated or prevented these changes and also normalized the reduced efficacy of norepinephrine and acetylcholine in isolated thoracic aortic rings of DOCA-salt hypertensive rats. This study suggests that a functional NO deficit in blood vessels and heart due to decreased NO synthase activity or increased release of reactive oxygen species such as superoxide may be a key change initiating many aspects of the cardiovascular impairment observed in DOCA-salt hypertensive rats. These changes can be prevented or attenuated by administration of l-arginine.     

Enhanced formation of PGI2, a potent hypotensive substance, by aortic rings and homogenates of the spontaneously hypertensive rat.

Intact rings and homogenates of aorta from spontaneously hypertensive rats (SHR) contain enhanced capacity over normal rats (NR) to convert arachidonic acid into PGI2. The PGI2 synthetic system in SHR is stimulated to a greater extent than NR by norepinephrine. Indomethacin blocks this stimulation. PGE2 and PGF2alpha were detected in much smaller amounts in homogenates (undetected in rings) but their formation was not enhanced by the hypertensive tissue. The identity of PGI2 was based on 1) direct pharmacological assay on the rat blood pressure. In this system identical vasodepressor responses to PGI2 are observed after intracarotid and intrajugular administration 2) indirectly as 6-keto PGF1alpha isolated after incubation of aortic homogenates with tritiated arachidonic acid and 3) indirectly by GC-MS assay of PGE2, PGF2alpha and 6-keto PGF1alpha formed during incubation of aortic homogenates with excess unlabeled arachidonic acid. These results provide additional support to our recent hypothesis that PGI2, of aortic origin, might actively participate in the regulation of systemic blood pressure. Its enhanced formation by intact hypertensive vascular tissue reflects an increase in the number of enzyme molecules immediately available to the substrate. This could probably be an adaptive response to the elevated levels of catecholamines in the circulation.     

Hypertensive factor: calcium stimulatory activity obtained from different tissues and animal species

It was recently shown that a peptide (hypertensive factor, HF) isolated from erythrocyte hemolysates from spontaneously hypertensive rats induced a prolonged elevation of blood pressure in normotensive rats. In addition, the peptide produced a marked stimulation of the in vitro uptake of lanthanum-resistant calcium by the aortae and enhanced the contractile response of aortic rings to constrictor agents. The present report describes findings of calcium stimulatory activity, enhancement of contractile function, or pressor activity in extracts of homogenates from several tissues of the rat and from erythrocyte hemolysates of several mammalian species. Significant stimulation of calcium uptake in aortic rings was obtained with preparations from rat brain, liver, and kidney. The activity per weight of tissue was similar for brain and kidney (approximately 2 units/g), while liver exhibited somewhat higher concentrations (4 units/g). The diffusate of cardiac tissue did not significantly alter in vitro calcium uptake by aortae. The injection of the cardiac and liver diffusates into normotensive Wistar-Kyoto rats produced slight (10 Torr) (1 Torr = 133.3Pa) and moderate (25 Torr) elevations of blood pressure, respectively. Finally, a peptide purified from homogenates of rat brain by the protocol developed for the purification of HF from erythrocytes was shown to significantly enhance the contractile response of aortic rings to K+ and norepinephrine. Diffusates of erythrocytes from the rat, rabbit, dog, and guinea pig each caused a significant stimulation of calcium uptake and contained approximately the same level of activity (500 units/L of whole blood). Diffusates prepared from outdated human erythrocytes had no significant effect on calcium uptake, whereas those of freshly drawn samples exhibited high levels of activity.(ABSTRACT TRUNCATED AT 250 WORDS)     

Low-Dose Dextromethorphan,a NADPH Oxidase Inhibitor,Reduces Blood Pressure and Enhances Vascular Protection in Experimental Hypertension

Background

Vascular oxidative stress may be increased with age and aggravate endothelial dysfunction and vascular injury in hypertension. This study aimed to investigate the effects of dextromethorphan (DM), a NADPH oxidase inhibitor, either alone or in combination treatment, on blood pressure (BP) and vascular protection in aged spontaneous hypertensive rats (SHRs).

Methodology/Principal Findings

Eighteen-week-old WKY rats and SHRs were housed for 2 weeks. SHRs were randomly assigned to one of the 12 groups: untreated; DM monotherapy with 1, 5 or 25 mg/kg/day; amlodipine (AM, a calcium channel blocker) monotherapy with 1 or 5 mg/kg/day; and combination therapy of DM 1, 5 or 25 mg/kg/day with AM 1 or 5 mg/kg/day individually for 4 weeks. The in vitro effects of DM were also examined. In SHRs, AM monotherapy dose-dependently reduced arterial systolic BP. DM in various doses significantly and similarly reduced arterial systolic BP. Combination of DM with AM gave additive effects on BP reduction. DM, either alone or in combination with AM, improved aortic endothelial function indicated by ex vivo acetylcholine-induced relaxation. The combination of low-dose DM with AM gave most significant inhibition on aortic wall thickness in SHRs. Plasma total antioxidant status was significantly increased by all the therapies except for the combination of high-dose DM with high-dose AM. Serum nitrite and nitrate level was significantly reduced by AM but not by DM or the combination of DM with AM. Furthermore, in vitro treatment with DM reduced angiotensin II-induced reactive oxygen species and NADPH oxidase activation in human aortic endothelial cells.

Conclusions/Significance

Treatment of DM reduced BP and enhanced vascular protection probably by inhibiting vascular NADPH oxidase in aged hypertensive animals with or without AM treatment. It provides the potential rationale to a novel combination treatment with low-dose DM and AM in clinical hypertension.     

Expression of myogenic constrictor tone in the aorta of hypertensive rats

We investigated the effect of intraluminal pressure or stretch on the development of tone in the descending thoracic aorta from rats with aortic coarctation-induced hypertension of 7-14 days duration. Increments of pressure >100 mmHg decreased the diameter of thoracic aortas from hypertensive but not from normotensive rats. The pressure-induced constriction was not demonstrable in vessels superfused with calcium-free buffer. Stretched rings of aorta from hypertensive rats exhibited a calcium-dependent constrictor tone accompanied by elevated calcium influx that varied in relation to the degree of stretch. Blockers of L-type calcium channels and inhibitors of protein kinase C reduced both basal tone and calcium influx in aortic rings of hypertensive rats. Hence, the thoracic aorta of hypertensive rats expresses a pressure- and stretch-activated constrictor mechanism that relies on increased calcium influx through L-type calcium channels via a protein kinase C-regulated pathway. The expression of such a constrictor mechanism is suggestive of acquired myogenic behavior.     

胍丁胺对离体大鼠主动脉张力的影响及其受体机制

采用离体血管环灌流方法,观察了胍丁胺（agmatine,Agm)对大鼠胸主动脉张力的影响,并探讨其受体机制,实验结果如下：（1）在苯肾上腺素PE,10^-6mol/L)引起血管预收缩的 基础上,Agm(10^-7-10^-2mol/L)剂量依赖性地舒张大鼠胸主动脉。（2）上述舒张反应在去除内皮和应用NOS抑制剂N^-G-mnitro-L-arginine methyl ester(L-NAME,0.5mmol/L)后依然存在,提示Agm的舒血管作用为非内皮依赖性,并无NO的参与。（3）在高Ca^2 (3mmol/L)引起血管预收缩的基础上,Agm也可剂量依赖性地舒张大鼠主动脉。（4）预先应用α2－肾上腺素能受体（α2－adrenergic receptor,α2－AR）和咪唑啉受体（IR）阻断剂idazoxan(10^-4mol/L)则可完全阻断Agm的上述作用。（5）应用α2－AR拮抗剂yohimbine(10^-4mol/L)可部分阻断Agm对大鼠主动脉的舒张反应,以上结果表明,Agm对大鼠主动脉血管的舒张作用是由α2－AR和IR共同介导。     

Delayed development of hypertension and increased aortic relaxation in spontaneously hypertensive rats after neonatal sympathectomy

The effect of neonatal sympathectomy on vasodilator responses to acetylcholine (ACh) and cAMP has been studied in aortic rings of spontaneously hypertensive rats (SHR) and normotensive animals. The relaxation of intact SHR aorta in response to ACh and cAMP was 20-35% lower than that of normotensive rats. Sympathectomy in normotensive rats did not affect the level of blood pressure and aorta reactivity to Ach. In SHR, sympathectomy caused a decrease in blood pressure, while relaxation in response to ACh and cAMP increased, as compared to intact SHR, but remained lower than in normotensive rats. The data obtained suggest that the decrease in arterial pressure of sympathectomized SHR is a result not only of the reduction in sympathetic effects but also of the increase in smooth muscle relaxation.