HYPERRENINEMIC HYPOALDOSTERONISM AFTER CHRONIC STRESS IN THE RAT

The effects of chronic stress on the renin-angiotensin-aldosterone system were studied by analysis of plasma hormone levels, kidney renin mRNA levels, adrenal angiotensin II receptors, and steroidogenesis in rats subjected to repeated immobilization (2 h daily) or intraperitoneal injections of 1.5 M NaCl for 14 d. 24 h after the last stress in both stress models, plasma aldosterone levels were reduced in spite of significant increases in plasma renin activity. Repeatedly intraperitoneal hypertonic saline-injected rats showed plasma renin activity responses to acute immobilization similar to controls, but markedly reduced plasma aldosterone responses. Concomitant with the increases in plasma renin activity, renin mRNA levels in the kidney were significantly increased in intraperitoneal hypertonic saline-injected rats, and these increases were prevented by beta-adrenergic receptor blockade with propranolol. In isolated adrenal glomerulosa cells from chronically stressed rats, maximum aldosterone responses to angiotensin II, ACTH, and 8-Br-cAMP were significantly decreased, whereas pregnenolone responses were increased, P450-aldosterone synthetase mRNA levels and binding of I-125-[Sar(1),Ile(8)] angiotensin II were significantly reduced in the adrenal zona glomerulosa of stressed rats. These studies show that chronic repeated stress leads to renin stimulation due to sympathetic activation, and inhibition of aldosterone secretion due to inhibition of the late steroidogenic pathway. The data provide evidence for a role of chronic stress in the development of hyperreninemic hypoaldosteronism.