STEROID SECRETION--ROLE OF CALCIUM IN ADRENAL CELLS

该项目的中心假设是， 浓度（Cai）是醛固酮生物合成的主要调节因子 和分泌物。 在第一次授予期间， 肾上腺球状体（ZG）扩大到单细胞水平。 这些研究精确地量化了Cai发生变化的程度 在促分泌素刺激期间。 细胞外K+浓度升高 生理范围产生持续上升蔡，这可能是一个 这是电压依赖性Ca 2+通道激活的结果。 对 另一方面，Cai对血管紧张素II（AngII）的反应表现出一种 空间不均匀和时间振荡图案。 尽管 Cai反应的复杂性，我们的平行研究结果 比较醛固酮分泌的时间特征和CAI 进一步加强了钙离子调节醛固酮的假说。 本提案中的实验将采用单细胞Cai 测量和质膜，膜片钳电生理， 具体目的如下：（1）测定胞浆Ca ~（2+） ZG细胞Cai振荡模式的动员机制 由AngII刺激。 (2)为了确定质膜的作用 电位、电压和受体操纵的离子通道 或调制Cai振荡。 (3)为了研究 负责恢复蔡的基础水平后， 刺激上升。 醛固酮分泌的异常调节已经在一个研究中被报道。 大部分高血压人群，尤其是 对AngII输注的反应。 负责这些问题的机制 激素分泌的改变是未知的。 我们最近 证明了来自自发性高血压大鼠（SHR）的ZG细胞 静息钙离子浓度升高，对血管紧张素II的钙反应迟钝， K+施用，这表明持续增加的蔡可能是 与类固醇对促分泌素的反应改变有偶然关系。 这些发现为最后一个具体目标提供了基础：（4）测试 这一假说认为， 高血压状态部分是由于对基础和 单个ZG细胞中促分泌素修饰的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.