A Potential Role for Phospholipase-D in the Angiotensin-II-Induced Stimulation of Aldosterone Secretion from Bovine Adrenal Glomerulosa Cells

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 p...