Effect of rat atrial natriuretic factor on in vivo and in vitro aldosterone and corticosterone secretions in the rat during the perinatal period.

The effect of rat atrial natriuretic factor (rANF) on aldosterone and corticosterone secretion was investigated in vivo in 21-day-old rat fetuses injected intravenously through the umbilical vein and in vitro on isolated adrenal cells from 17-, 19- and 21-day-old fetuses and 1-, 2-, 3- and 4-week-old rats. In vivo, rANF (50 pmol/50 microliters/fetus) inhibited both basal levels and secretion of aldosterone stimulated by adrenocorticotropin hormone (ACTH(1-24), 0.25 pmol/50 microliters/fetus), but not corticosterone secretion. In vitro, the addition of graded concentrations of rANF (0.001, 0.01 and 10 nmol/l) to the incubation medium did not affect the basal aldosterone and corticosterone secretions of fetal and neonatal adrenal cells. ACTH(1-24) (0.1 nmol/l) stimulated productions of both corticosterone and aldosterone by the adrenal cells at all stages studied. The addition of graded concentrations of rANF to the incubation medium containing ACTH(1-24) (0.1 nmol/l) induced a dose-dependent inhibition of aldosterone secretion by the adrenal cells from 21-day-old fetuses and newborn rats. In contrast, no effect was observed on cells from 17- and 19-day-old fetuses. At all stages investigated, the three doses of rANF were unable to affect ACTH-induced corticosterone secretion in vitro. In isolated adrenal cells from 2-week-old rats, rANF (10 nmol/l) inhibited the secretion of aldosterone induced by ACTH(1-24) (0.1 nmol/l), and by different steroids of the aldosterone synthetic pathway (progesterone, 11-deoxycorticosterone, corticosterone, 1 mumol/l for each steroid). These results suggest that rANF is a specific inhibitor of aldosterone synthesis in the perinatal period of the rat and that the inhibitory effect of rANF occurs both during the early and late pathways of aldosteroidogenesis.