| Abstract: | In order to investigate the relative contribution of ACTH, the renin angiotensin and dopaminergic system to the circadian rhythm of plasma aldosterone, hormone levels were determined at hourly intervals over a 24 h span in four supine healthy men. Blood was withdrawn under basal conditions (control), after either dexamethasone, captopril or bromocriptine++ (CB-154) administration. Plasma aldosterone rhythmicity was abolished in dexamethasone treated groups but not in captopril or CB treated groups. Time dependent alterations of aldosterone regulators were analyzed by multiple regression methods at 3 hourly intervals. These results indicate that plasma aldosterone rhythmicity is predominantly under the control of ACTH whereas the renin angiotensin or dopaminergic system plays a little role. In supine, sodium repleted states, ACTH is a potent stimulus of aldosterone at 000-0600 h and 1700-1900 h clocktime, whereas during daytime renin-angiotensin is an additional regulator. |
