Aldosterone and renin inhibition by atrial natriuretic factor in potassium-loaded rats

This study was designed to determine the effects of synthetic rat atrial natriuretic factor (ANF) on plasma renin activity (PRA) and aldosterone secretion in separate groups of normal and potassium-loaded anesthetized rats. Control rats were fed a normal diet of sodium and potassium and had base-line levels of PRA and aldosterone secretion of 25 ± 3 ng angiotensin I (ANG I) · ml^-1 · h^-1 and 0.56 ± 0.09 ng/min, respectively. Chronic oral potassium loading for 10 days elevated the plasma potassium concentration, stimulated aldosterone secretion to 1.80 ± 0.18 ng/min (P < 0.05), and attenuated PRA to 13 ± 2 ng ANG I · ml^-1 · h^-1 (P < 0.05). Infusion of ANF at 45 ng · kg^-1 · min^-1 in potassium-loaded rats lowered aldosterone secretion to 1.32 ± 0.21 ng/min (P < 0.05) but did not significantly reduce PRA (11 ± 2 ng ANG I · ml^-1 · h^-1 (P > 0.05). A higher ANF infusion dose of 100 ng · kg^-1 · min^-1 produced a further decrement in aldosterone secretion to 1.15 ± 0.26 ng/min (P < 0.05) and also reduced PRA to 3 ± 1 ng ANG I · ml^-1 · h^-1 (P < 0.05). In the control rats, aldosterone secretion and PRA were decreased significantly during infusion with both low and high ANF doses. Base-line arterial pressures among experimental groups were not different (P > 0.05) and did not change during infusion of ANF in any group. These results indicate that ANF can inhibit chronic potassium-stimulated aldosterone secretion in the rat independently of its inhibitory actions on renin release.