Bollag W B, Barrett P Q, Isales C M, Liscovitch M, Rasmussen H
Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, Connecticut 06510.
Endocrinology. 1990 Sep;127(3):1436-43. doi: 10.1210/endo-127-3-1436.
The mechanism by which angiotensin-II (Ang II) stimulates aldosterone secretion from adrenal glomerulosa cells involves a phospholipase-C-mediated increase in phosphoinositide turnover and diacylglycerol (DAG) production. Because agonist-induced activation of phospholipase-D (PLD) also contributes to elevations in DAG in other cell types, the ability of Ang II to stimulate PLD activity in cultured bovine adrenal glomerulosa cells was examined. Ang II elicited significant increases in the levels of phosphatidic acid and, in the presence of ethanol, of phosphatidylethanol, a more specific marker for PLD activation. The potential role of this increased PLD activity in the regulation of aldosterone secretion was examined by investigating the ability of exogenous PLD to alter secretory rates. PLD alone dose-dependently increased aldosterone secretion from 5.9 +/- 0.5 to 135 +/- 48 pg/min.mg protein. In the presence of the calcium channel agonist Bay K 8644, which by itself had only a modest effect on aldosterone production, the stimulatory action of PLD was enhanced, yielding a secretory rate (442 +/- 119 pg/min.mg protein) that was approximately 60% of that elicited by 10 nM Ang II (763 +/- 182 pg/min.mg protein). Exogenous PLD also induced a significant increase in DAG levels (from 0.76 +/- 0.03 to 1.10 +/- 0.1 nmol/mg protein), which was not altered by the addition of Bay K 8644. However, PLD did not stimulate inositol phosphate production. These data indicate that 1) Ang II activates PLD; 2) exogenous PLD can elevate aldosterone secretory rates and DAG levels without eliciting phosphoinositide hydrolysis; and 3) the stimulatory action of exogenous PLD on aldosterone secretion is enhanced in the presence of Bay K 8644. Thus, PLD-induced DAG production may play an important role in the Ang II-mediated stimulation of aldosterone secretion from the adrenal zona glomerulosa.
血管紧张素-II（Ang II）刺激肾上腺球状带细胞分泌醛固酮的机制涉及磷脂酶-C介导的磷酸肌醇周转率增加和二酰基甘油（DAG）生成。由于激动剂诱导的磷脂酶-D（PLD）激活也有助于其他细胞类型中DAG水平的升高，因此研究了Ang II刺激培养的牛肾上腺球状带细胞中PLD活性的能力。Ang II引起磷脂酸水平显著升高，并且在存在乙醇的情况下，磷脂酰乙醇水平也显著升高，磷脂酰乙醇是PLD激活的更特异性标志物。通过研究外源性PLD改变分泌速率的能力，探讨了这种增加的PLD活性在醛固酮分泌调节中的潜在作用。单独的PLD以剂量依赖性方式将醛固酮分泌从5.9±0.5增加到135±48 pg/min·mg蛋白。在钙通道激动剂Bay K 8644存在的情况下，其本身对醛固酮生成只有适度影响，PLD的刺激作用增强，产生的分泌速率（442±119 pg/min·mg蛋白）约为10 nM Ang II引起的分泌速率（763±182 pg/min·mg蛋白）的60%。外源性PLD还导致DAG水平显著升高（从0.76±0.03增加到1.10±0.1 nmol/mg蛋白），添加Bay K 8644对此没有改变。然而，PLD并未刺激肌醇磷酸的生成。这些数据表明：1）Ang II激活PLD；2）外源性PLD可提高醛固酮分泌速率和DAG水平，而不引起磷酸肌醇水解；3）在Bay K 8644存在的情况下，外源性PLD对醛固酮分泌的刺激作用增强。因此，PLD诱导的DAG生成可能在Ang II介导的肾上腺球状带醛固酮分泌刺激中起重要作用。
