STEROID SECRETION--ROLE OF CALCIUM IN ADRENAL CELLS

该项目的中心假设是胞内游离钙 浓度(Cai)是醛固酮生物合成的主要调节因子。 和分泌物。在第一次资助期间，对蔡铭超的调查 肾上腺球状带(ZG)延伸至单细胞水平。 这些研究精确地量化了所发生的cai变化的程度。 在促分泌剂刺激过程中。ITS中细胞外K+的升高 生理范围产生持续的CAI上升，这可能是一个 这是电压依赖性钙通道激活的结果。在……上面 另一方面，血管紧张素II(AngII)的血管紧张素转换酶(CaI)反应表现为 空间不均匀且在时间上振荡的图案。尽管 蔡氏反应的复杂性，我们的平行研究结果 醛固酮分泌与血管紧张素转换酶时间特征的比较 进一步强化了钙离子对醛固酮调节的假说。 本方案中的实验将使用单细胞cai。 测量和质膜、膜片钳电生理 解决以下具体目标：(1)确定细胞内钙离子 ZG细胞CaI振荡模式的动员机制 在安吉的刺激下。(2)确定质膜的作用 控制电位、电压和受体操作的离子通道 或者是对蔡氏振荡进行调制。(3)探讨其作用机制。 负责将CAI恢复到基础水平 受刺激的上升。 据报道，醛固酮分泌的异常调节 很大一部分高血压人群，特别是在 对血管紧张素转换酶注射的反应。导致这些问题的机制 荷尔蒙分泌的变化尚不清楚。我们最近做了 证明自发性高血压大鼠(SHR)的ZG细胞 静息蔡升高，对Angii和Angii的钙反应迟钝 K+的应用，表明持续增加的CaI可能是 随意地与分泌剂引起的类固醇反应改变有关。 这些发现为最后一个具体目标提供了基础：(4)测试 有一种假说认为，这种疾病的病理生理后果 高血压状态的结果，部分是由于对基础和 促分泌剂修饰的单个ZG细胞中的CaI水平。

The central hypothesis of this project is that cytosolic free calcium concentration (Cai) is the major regulator of aldosterone biosynthesis and secretion. In the first grant period, investigation of Cai in adrenal zona glomerulosa (ZG) was extended to the single cell level. These studies precisely quantitated the extent of Cai changes that occur during secretagogue stimulation. Elevation of extracellular K+ in its physiological range produces a sustained rise in Cai that is probably a consequence of the activation of voltage-dependent Ca2+ channels. On the other hand, the Cai response to angiotensin II (AngII) exhibits a spatially non-uniform and temporally oscillating pattern. Despite the complexity of the Cai responses, our results from parallel studies comparing the temporal characteristics of aldosterone secretion and Cai have further strengthen the Ca2+ hypothesis for aldosterone regulation. The experiments in the present proposal will employ single cell Cai measurement and plasma membrane, patch-clamp electrophysiology to address the following Specific Aims: (1) To determine if cytosolic Ca2+ mobilization mechanisms underlie the oscillatory pattern of ZG cell Cai stimulated by AngII. (2) To determine the role of plasma membrane potential and voltage- and receptor operated ion channels in controlling or modulating the Cai oscillations. (3) To investigate the mechanisms responsible for the restoration of Cai to basal levels following a stimulated rise. Abnormal regulation of aldosterone secretion has been reported in a substantial fraction of the hypertensive population, particularly in response to AngII infusion. The mechanisms responsible for these alterations in hormonal secretion are unknown. We have recently documented that ZG cells from the spontaneously hypertensive rat (SHR) have an elevated resting Cai and a blunted calcium response to AngII and K+ application, suggesting that a sustained increase in Cai may be casually related to the altered steroid response to secretagogues. These findings provide the basis for the last Specific Aim: (4) To test the hypothesis that the pathophysiological consequences of the hypertensive state result, in part, from effects on basal and secretagogue-modified Cai levels in single ZG cells.