DHEA-sulfate causes a phase-dependent increase in melatonin secretion: A study of perifused rat pineal glands

Steroid hormones affect various metabolic activities, including melatonin s ynthesis, in mammals and nonmammals. We report here the effects of dehydroe piandrosterone (DHEA) and DHEA-sulfate (DHEA-S), two steroids with weak and rogen potency, on the levels of isoproterenol-stimulated melatonin released by perifused rat pineal glands removed in the middle of the light and dark spans [7 and 19 Hours After Light Onset (HALO), respectively] in a L/D 12: 12 regimen. DHEA-S but not DHEA was found to have a direct action on beta-a drenergic-stimulated melatonin release. DHEA-S increased melatonin secretio n (by 50-80%) dose-dependently in pineals obtained during the light span. T his effect depended on the circadian stage, because at night (19 HALO), onl y the highest concentration (10(-3) M) of DHEA-S increased melatonin secret ion (by 25%). In contrast, DHEA had no effect on melatonin release in pinea ls obtained during the light span. This work shows that DHEA-S but not DHEA was able to stimulate melatonin secretion by adrenergic-stimulated pineals removed during the light phase. It also suggests that the effects observed , or their intensity, or both depend on the circadian stage. (C) 2000 Elsev ier Science Inc. All rights reserved.