Effect of awakening on aldosterone.

Overnight studies conducted in 10 male volunteers showed that the effect of awakening on aldosterone and its main regulatory hormonal systems depends on the time of its occurrence. Waking periods in the latter half of the night induced concomitant increases in plasma levels of aldosterone and ACTH, whereas plasma renin activity tended to decrease. No effect was apparent, when subjects were awoken during the first hours of sleep, which is known to be a quiescent period of adrenocorticotropic activity. These results provide evidence of the dominant influence of ACTH during the second half of the night insuring the regulation of aldosterone during waking periods.