Effect of melatonin on androgen receptor and catalase mRNA

Among the various effects that have recently been demonstrated for melatonin is the regulation of several mRNAs, the control of at least some of them being mediated by the nuclear receptor for this hormone. The Harderian gland is a secondary sexual organ under androgenic control whose physiology is also regulated by melatonin, the action of melatonin being similar to that of androgens. This raises the question of whether melatonin regulates the mRNA for the androgen receptor. In the present work, using Northern blot techniques we found that melatonin regulates that mRNA when administered both acutely and chronically. When given chronically, melatonin displayed the androgenic actions previously reported by others to accompany androgen administration. We also report an effect of melatonin on catalase mRNA that parallels its effect on androgen receptor mRNA, suggesting that the action of melatonin on catalase mRNA might not be direct but, instead, an effect of the changes induced by this hormone in androgen receptor mRNA. It is known that nuclear receptors and their ligands in general interact with each other. We report the regulation of androgen receptor mRNA by melatonin and propose the hypothesis that this hormone would regulate steroid receptors in general or would interact with these receptors or their ligands. This hypothesis would explain both the classic studied effects of melatonin, mainly on the reproductive system, and some of the more recently found actions of this agent.