Effects of angiotensin-II and potassium on phospholipid metabolism in the adrenal zona glomerulosa.

We examined further the ffects of angiotensin-11 and K+ on phospholipid metabolism in the adrenal zona glomerulosa. In adrenal zona glomerulosa cell preparations, physiological and supraphysiological concentrations of angiotensin-I1 (10"2-10-4 M) and K+ (0-16 m ~ ) elicited doseand time-dependent increases in aldosterone production and (32P)phosphate incorporation into chromatographically purified phosphatidic acid and phosphatidylinositol; the stimulatory effect on the phosphatidate-inositide cycle was relatively specific as there were no apparent changes in (32P)phosphate labeled in areas of the chromatogram containing the major phospholipids, phosphatidylcholine and phosphatidylethanolamine. Angiotensin-11 also stimulated the turnover of prelabeled (S2P)phosphatidylinositol in vitro, and treatment in vivo with a diuretic (provoking Na+ depletion and stimulation of endogenous angiotensin-11 secretion) was attended by 2-3-fold increases in phosphatic acid, phosphatidylinositol, and polyphosphoinositides, and lesser increases in other phospholipids. Thus, the stimulatory effect of angiotensin-I1 on (32P)phosphate labeling observed in vitro may be due to stimulation of two processes, uiz. phosphatidylinositol hydrolysis (with a subsequent increase in phosphatidate synthesis) and de novo synthesis of phosphatidic acid. Cycloheximide inhibited aldosterone production and blocked the angiotensin-11-induced increases in (32P)phosphate incorporation into phosphatidic acid and phosphatidylinositol. Thus, similar to our findings in studies of adrenocorticotropin hormone action in the zona fasciculata-reticularis, a labile protein appears to be required for the stimulation of phospholipid metabolism during angiotensin-I1 action in the zona glomerulosa. The present findings provide further evidence to support the possibility that phospholipids play an important role in the stimulation of aldosterone synthesis by angiotensin-11 and K+.