Dopaminergic control of plasma catecholamine and aldosterone responses to acute stimuli in normal man

This study examines the influence of dopamine on catecholamine and aldosterone secretion in normotensive individuals. The responses of plasma aldosterone (PA), norepinephrine (NE), and PRA to upright posture and isometric handgrip were studied in five normal males on a constant 50-meq Na intake before and after 4 days of administration of the dopamine agonist, bromergocriptine (BEC; 2.5 mg three times a day). In addition, the PA responses to graded angiotensin II and ACTH infusions were examined before and during BEC. Supine PA and PRA were not altered by BEC, but basal NE was reduced significantly (P < 0.01) from 204 +/- 29 to 98 +/- 12 pg/ml after BEC. There was an accompanying significant reduction in upright mean arterial pressure during BEC administration. The PA and NE during upright posture and isometric handgrip were significantly suppressed by BEC, but PRA responses were unaltered. BEC produced a significiant (P < 0.025) suppression of the PA response to graded angiotensin II infusions but did not alter the PA response to graded ACTH. Our findings indicate that in normal man there is a pronounced inhibitory effect of dopaminergic pathways on catecholamine scretion and regulation of upright mean arterial pressure. Results of the posture study would suggest that dopamine-mediated PA alterations occur independently of changes in the levels of PRA. The finding that BEC suppressed PA responses to angiotensin II and posture but not to ACTH would imply that dopamine selectively exerts its effect or adrenal angiotensin II-mediated aldosterone secretion.