Heterogeneity of Glycosylation of Circulating Active and Inactive Renin

ABSTRACT

Concanavalin A chromatography was used to examine rat plasma and the incubation medium of rat renal cortical slices, the objective being to assess the heterogeneity of glycosylation of active and inactive renin. Inactive renin was measured by activation with trypsin. Concanavalin A chromatography could separate both active and inactive renin in the plasma into three forms, including the unbound form, the loosely-bound form and the tightly-bound form, thereby suggesting the presence of differently glycosylated forms of active and inactive renin in the plasma. Rat renal cortical slices secreted all these three forms of active and inactive renin, hence these forms are mainly of renal origin. These results suggest that differently glycosylated forms of active and inactive renin are released from the kidney into the blood circulation.     

Potential Functions of Plasma Prorenin; Regional Activation and Tissue Extraction

The fate of circulating inactive prorenin was examined in patients and volunteers. Prorenin was activated either by acid-dialysis with warming at pH 3.3 or with trypsin. The results were similar but omission of warming reduced the value by 13%. In 6 volunteers, 20 min forearm venous occlusion raised regional total (T) and inactive (I) plasma renin concentration (PRC) by 51% and 48% without change of active (A) renin. During intense foream exercise the ratio APRC:IPRC did not change in muscle or skin venous blood. Body anaerobic exercise increased APRC 3.7-fold without change in IPRC. These procedures activate plasminogen but are without effect on prorenin. In 18 patient with stable angina, TPRC was lower in coronary sinus than arterial blood (p<0.001) but APRC was not affected. A-V differences were not detected across the leg. Prorenin is apparently stable in the circulation but extracted by the heart.     

Primary Aldosteronism: A New Understanding

Primary aldosteronism (PAL) may always have a genetic basis. This leads to either abnormally regulated, increased biosynthesis (Familial Hyperaldosteronism Type I, FHI) or to unrestrained hyperplasia and neoplasia, usually benign. The distinction between diffuse hyperplasia, nodular hyperplasia and adenoma may be relatively unimportant in functional and etiological terms. The genetic basis must be understood before diagnosis of disease (FHI) or of predispostion (all other PAL) can be made at birth and appropriate surveillance commenced. The natural history of PAL other than FHI is for a progressive increase in severity, with both adrenals eventually involved. Long-term follow-up of PAL is therefore mandatory, and postoperative assessment of residual non-suppressible aldosterone production by fludrocortisone suppression testing useful in defining biochemical cure or improvement, and the need for specific medical treatment.     

前列腺素E2在肾脏球旁器调节肾素分泌中的作用

目的 观察前列腺素E2（PGE2）对肾脏球旁器颗粒细胞（JGG）肾素分泌的调节作用。 方法 将小鼠肾脏致密斑细胞株（MMDD1）种植在特殊滤器上,滤器上下（细胞顶侧和基底侧）分别用不同培养基培养细胞,改变细胞顶侧培养基中钠离子、氯离子和血管紧张素Ⅱ（AngⅡ）浓度,分别测定不同时间点滤器上、下PGE2浓度。腹腔注射卡托普利（30 mg/kg）前后,放射免疫法测定野生型和环氧化酶基因敲除（COX-2-/-）小鼠血浆肾素活性(PRA)变化;原代分离COX-2-/-小鼠JGG,测定细胞上清肾素活性及其对PGE2刺激的反应。实时定量PCR测定低肾素（JGG细胞特异性Gsα基因缺失）小鼠肾脏皮质COX-2 mRNA表达。免疫组化法检测肾皮质COX-2蛋白表达。代谢笼中留取24 h尿,ELISA方法测定PGE2水平。 结果 (1)低氯刺激能使致密斑细胞分泌PGE2,不论基底侧还是细胞顶端PGE2浓度均显著增加（均P < 0.05）;但AngⅡ对致密斑分泌PGE2没有显著影响;(2)COX-2-/-小鼠基础PRA[（378.3±96.4）比（1115.0±210.0） ng AngI&#8226;ml-1&#8226;h-1,P ＝ 0.0051,n＝10]和JGG细胞肾素分泌[（153.7±14.7）比（672.4±129.0） ng AngI&#8226;ml-1&#8226;h-1,P ＝ 0.0162,n＝3]显著低于相同遗传背景的野生型小鼠;卡托普利能刺激COX-2-/-小鼠PRA增加32.8倍;PGE2能部分恢复COX-2-/-小鼠原代JGG细胞分泌肾素功能;(3)PGE2受体EP4耦联的Gsα基因敲除的低肾素小鼠,肾脏皮质COX-2 mRNA表达增加（8.07±1.08)倍（n=6,P = 0.0022),免疫组化显示致密斑和远端小管COX-2蛋白表达增加,24 h尿PGE2分泌增加[（1235±152） pg/24 h 比（385±140） pg/24 h,P = 0.0065]。 结论 致密斑PGE2直接受低氯调节,COX-2-/-小鼠基础肾素减少;下游的AngⅡ能直接作用于JGG细胞而不是致密斑负反馈调节肾素分泌。阻断JGG细胞自身的肾素产生（Gsα基因敲除）后,能负反馈上调致密斑的COX-2表达,故COX-2-PGE2-肾素在球旁器存在近距离精确调控机制。     

局部肾素与血管紧张素原mRNA在肝硬化门静脉高压症患者中的表达及其意义

目的探讨肝硬化门静脉高压症 (PH)对局部肾素血管紧张素系统 (LRAS)活性的影响。方法采用逆转录聚合酶链反应方法检测肝硬化门静脉高压症患者肝脏、脾脏动、静脉组织局部肾素与局部血管紧张素原mRNA的表达情况。结果　对照组内局部肾素mRNA在肝脏中最低(0 19± 0 12 ) ,显著低于脾脏动、静脉组织 [(0 4 5± 0 12 )及 (0 39± 0 12 ) ],P <0 0 5 ;局部血管紧张素原mRNA以肝脏最高 (0 6 4± 0 2 1) ,显著高于脾脏动、静脉组织 [(0 32± 0 15 )及 (0 4 1± 0 18) ],P <0 0 5。肝硬化门静脉高压症组肝脏、脾动脉、脾静脉局部肾素mRNA分别为 (0 78± 0 2 8)、(0 86± 0 35 )、(0 81± 0 2 2 ) ,显著高于对照组 ,P <0 0 5 ;肝硬化门静脉高压症组肝脏、脾动脉、脾静脉局部血管紧张素原mRNA量分别为 (0 96± 0 2 5 )、(0 83± 0 18)、(0 79± 0 2 3) ,亦显著高于对照组 ,P<0 0 5。结论肝硬化门静脉高压患者局部肾素与血管紧张素原mRNA表达增强 ,并可能促进肝硬化门静脉高压症时内脏血管病变的形成。     

血管紧张素Ⅱ调节肾脏球旁器颗粒细胞合成肾素的机制研究

目的 观察血管紧张素Ⅱ（AngⅡ）对肾脏球旁器颗粒细胞肾素分泌的调节作用。 方法 密度梯度离心原代分离小鼠肾小球球旁器颗粒细胞（JGC）。实时定量PCR法检测JGC内血管紧张素转换酶（ACE）、AngⅡ受体（AT）1型和2型（AT1和AT2） mRNA表达。不同浓度的AngⅡ与球旁器细胞共孵育后,放射免疫法测定上清中肾素活性;实时定量PCR法测定细胞内肾素mRNA表达;化学发光法测定细胞内、外环磷酸腺苷（cAMP)水平的剂量和时间效应。改变细胞内钙离子浓度后,观察JGC内和上清中cAMP浓度改变。实时定量PCR法检测AngⅡ对JGC内腺苷酸环化酶（AC）5和AC6 mRNA表达的影响。 结果 成功分离的JGC存在ACE、AT基因表达。AngⅡ可抑制JGC肾素分泌[（370.6±36.9）比（299.6±25.7） ng AngI&#8226;ml-1&#8226;h-1,P = 0.014],并能抑制基础状态和前列腺素E2、去甲肾上腺素诱导的肾素mRNA表达。AngⅡ剂量依赖地降低JGC内和上清中cAMP水平。内质网上的Ca-ATP泵抑制剂毒胡萝卜内酯和环盐酸吗甲吡嗪酸均能剂量依赖地降低cAMP水平。细胞内钙离子螯合剂BAPTA-AM可降低细胞内钙离子浓度,进而使细胞内cAMP水平显著升高[（11.09±0.48）比（3.55±0.47） nmol/L,P < 0.01]。AngⅡ能通过减少42.12%的AC5 mRNA 表达,进而抑制肾素分泌。 结论 AngⅡ直接抑制肾素分泌可能是通过影响AC5,进而抑制cAMP表达来实现的。JGC内调节肾素分泌过程中,钙离子途径和GSα-cAMP两大信号传导途径中存在交联对话。     

尿液水通道蛋白-2与低肾素型高血压关系的研究

目的探讨水通道蛋白-2（AQP2）与低肾素型高血压（LREH）发病机制的关系。方法选取LREH患者110例,分为1、2、3级高血压三个亚组,设置健康对照40例,间接ELISA法检测尿液AQP2浓度,放射免疫法检测血浆血管加压素（AVP）浓度,监测平均动脉压（MAP）,分析患者尿液AQP2浓度的变化及其与血浆AVP浓度、MAP之间的关系。结果LREH组不同血压级别三个亚组血浆AVP浓度、尿液AQP2浓度均高于健康对照组（t=2.99、t=3.01,P〈0.05）,并随血压级别升高而升高（P均〈0.05）;尿液AQP浓度与血浆AVP浓度、MAP之间彼此均呈正相关（r=0.862、r=0.694、r=0.797,P〈0.05）。结论LREH患者肾脏集合管主细胞内AQP2穿梭、表达的增加,可能与LREH的水钠潴留机制密切相关.     

Morphological evidence of exocrine function in coagulating gland renin of mouse strain C57BL/6

Background: Renin is classically secreted from juxtaglomerular cells of the kidney by endocrine or paracrine mechanisms. In a previous report, intense renin immunoreactivity was observed in the coagulating gland (CG), a new source for renin in mice. In the present study, immunoelectron microscopical analysis for renin was carried out to clarify the secretory site of CGs. Methods: Five adult male C57BL/6 mice were used in this study. The CGs were fixed with an ice-cold 2% glutaraldehyde and 2% paraformaldehyde mixture and embedded in Lowicryl K4M. Ultrathin sections were treated with antimouse renin antiserum and colloidal gold (15 nm)-labeled protein A complex. Results: In immunoelectron microscopical observation, renin was first detected at the Golgi vacuoles just budding from the lamellae, although it was not demonstrated in all Golgi vacuoles. In the production series of exocrine granules, renin immunoreactivity was observed in some granules that were distributed in the supranuclear region. Both renin-positive and negative exocrine granules were secreted from the apical cell membrane by exocytosis. The lysosomal granules also showed stronger renin immunoreactivity and contained homogeneous or heterogeneous materials. In the supranuclear region, it was observed that exocrine granules were fused with irregular lysosomal granules. At the apical region, such lysosomal granules were closely associated with cell membrane. At the basolateral region, immunoreactivity for renin was localized in electron dense granules. Conclusions: These results suggest that part of the renin in the CGs is released by exocrine secretion into the genital tract. © 1995 Wiley-Liss, Inc.