Modulation of aldosterone secretion in frusemide-induced hypokalaemia

To study the effect of hypokalaemia in the regulation of aldosterone secretion, repeated injections of frusemide (3 mg/kg) plus saline with or without simultaneous infusion of potassium chloride (1 mEq/kg/h) were performed in 24 conscious female rabbits for 7 h. Without potassium supplementation, the plasma renin activity (PRA) remained elevated throughout the study, while an initial increase (1 h to 3 h) in plasma aldosterone (PA) gradually returned to normal with reduction of the serum potassium. In rabbits on potassium supplements to prevent the development of hypokalaemia, both PRA and PA remained elevated. The incremental aldosterone response to administration of potassium chloride, angiotensin II or ACTH, was considerably smaller in potassium-depleted rabbits than in potassium-repleted rabbits. These results suggest that serum potassium modulates the effects of angiotensin II or ACTH on aldosterone secretion, and that a certain level of potassium is necessary to maintain the aldosterone secretory capacity of the adrenal gland.