Effect of atrial natriuretic hormone on metoclopramide-induced stimulation of aldosterone

The effect of atrial natriuretic hormone (ANH) on metoclopramide-induced stimulation of aldosterone was studied in eight healthy young men after 3 days of controlled diet (150 mEq sodium, 100 mEq potassium). Baseline values were obtained after subjects had remained sitting for 1 hour. Subjects then received 2-hour infusions of placebo, dopamine (2 micrograms/kg/min), ANH (0.6 pmol/kg/min), and ANH plus dopamine. One hour after the beginning of each infusion, a 10 mg intravenous bolus of metoclopramide was given. Prolactin levels increased 10-fold after metoclopramide with placebo infusion, and about 50% of this stimulation was abolished by preinfusion with dopamine. ANH preinfusion did not suppress prolactin release. Urinary sodium excretion increased prominently during dopamine infusion. ANH at this dose had no effect on natriuresis. The dopamine dose given had almost no effect on metoclopramide-induced aldosterone secretion, whereas ANH infusions, which resulted in approximate doubling of plasma ANH levels, suppressed aldosterone. This study supports a role of ANH in aldosterone regulation, even at nonnatriuretic doses, and suggests that ANH is acting not only through the renin-angiotensin system but under certain conditions has significant physiologic action directly on glomerulosa cells.