The effect of metoclopramide and haloperidol on plasma renin activity and aldosterone levels in rats.

To gain further information on dopaminergic inhibition of renin release and aldosterone secretion, we studied the effect of 0.1, 1.0, or 5.0 mg metoclopramide or haloperidol/kg body weight i.p. on plasma renin activity (PRA) and aldosterone concentration in serum, and of furosemide pretreatment or dietary sodium restriction (14 days) on PRA and aldosterone responses to 1.0 and 5.0 mg haloperidol/kg b.wt. i.p. in groups of eight male Sprague-Dawley rats. Aldosterone levels in serum were increased very similarly by 0.1 and 1.0 mg metoclopramide and haloperidol/kg. Whereas PRA and aldosterone were unaffected by 5.0 mg metoclopramide/kg, both were maximally stimulated by 5.0 mg haloperidol/kg. Furosemide pretreatment increased PRA and aldosterone concentration and blunted the aldosterone response to haloperidol. PRA response to 5.0 mg haloperidol/kg was not changed. After sodium restriction, aldosterone concentration as inappropriately high and did not respond to 1.0 mg haloperidol/kg. However, PRA and aldosterone response to 5.0 mg haloperidol/kg was magnified. Our study confirms both dopaminergic inhibition of PRA and stimulation of aldosterone secretion by dopamine antagonists in rats. A feedback regulatory mechanism becomes conceivable which comprises aldosterone secretion, sodium turnover, volume homeostasis, and dopaminergic activity.