In Vitro Effects of Melatonin and Serotonin on Adrenal Steroidogenesis

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Abstract
The effects of melatonin and serotonin on adrenal steroidogenesis were studied. Adrenals were obtained from 42 day old intact female Long-Evans rats maintained under a photoperiod of 12 h light:12 h dark. Tissue slices and homogenates were incubated in the presence of 45 nmol/ml of melatonin or serotonin. Melatonin stimulates reductase activity. As a consequence secretion rates of dihydrocorticosterone and tetrahydrocorticosterone increase with a concomitant decline in proportionate secretion of corticosterone. Serotonin does not alter any of these parameters of adrenal steroidogenesis. ACTH, prolactin, GH [growth hormone], testosterone and estradiol have long been known to inhibit 5.alpha.-reductase activity. The stimulatory influence of melatonin stands in striking contrast to the effects of these hormones.