Effects of atrial natriuretic factor on corticosteroid and catecholamine secretion by the adrenals of Xenopus laevis.

The effects of atrial natriuretic factor (ANF) on the adreno-corticosteroid and catecholamine secretion of Xenopus laevis were studied in vitro and in vivo. In vitro, the effects of rANF(99-126), from 0.1 to 50 nM, on corticosteroid secretion was investigated using a perifusion system. The basal secretion of aldosterone but not corticosterone was dose dependently decreased. A prolonged perifusion with 1 nM rANF(99-126) alternated ACTH(1-28) stimulation of secretion of both corticosteroids. Only ANF analogues with intact disulfide bridges (rANF(99-126), hANF(99-126), Atriopeptin II, frogANF(21)), and an extract of Xenopus laevis hearts significantly inhibited aldosterone release; the N-terminal (99-109) and the C-terminal ANF(116-126) fragments had no effects. In vitro norepinephrine (NE) and epinephrine (E) were released but dopamine (D) was not detected. rANF(99-126) at concentrations up to 1 microM affected neither basal nor acetylcholine stimulated catecholamine secretion. In vivo, a single injection of 3 nmol rANF(99-126) per 100 g body weight was given and the serum concentrations of corticosterone, aldosterone, D, NE, and E were determined 1, 3, 6, 12, and 24 hr later. Both steroids decreased after 12 hr, whereas the catecholamine concentrations were not significantly changed. ANF is concluded to act on steroidogenic but not chromaffin cells in Xenopus laevis.