This study was designed to investigate the role of dopaminergic mechanisms in the control of aldosterone secretion in man. Five normal male subjects in metabolic balance at 150 meq sodium/d and 60 meq potassium/d constant intake received the specific dopamine antagonist, metoclopramide, 10 mg i.v. on 2 consecutive d. On the 1st d, the subjects received an infusion of 5% glucose solution (vehicle) from 60 min before to 60 min after metoclopramide administration; on the 2nd d, an infusion of dopamine 4 μg/kg per min was substituted for vehicle. Metoclopramide in the presence of vehicle increased plasma aldosterone concentrations from 2.4±1.1 to a maximum of 17.2±2.8 ng/100 ml (P < 0.01) and serum prolactin concentrations from 7.5±5.0 to a maximum of 82.2±8.7 ng/ml (P < 0.01). Dopamine 4 μg/kg per min did not alter basal plasma aldosterone concentrations, but blunted the aldosterone responses to metoclopramide significantly; in the presence of dopamine, plasma aldosterone concentrations increased from 3.1±0.5 to 6.2±1.4 ng/100 ml (P < 0.05) in response to metoclopramide. The incremental aldosterone responses to metoclopramide were significantly lower in the presence of dopamine than with vehicle. Dopamine 4 μg/kg per min suppressed basal prolactin to <3 ng/ml and inhibited the prolactin responses to metoclopramide; serum prolactin concentrations increased to a maximum of 8.5±2.3 ng/ml with metoclopramide in the presence of dopamine.
Robert M. Carey, Michael O. Thorner, Elizabeth M. Ortt