In vitro modulation of steroidogenesis and gene expression by melatonin: a study with porcine antral follicles.

The effects of melatonin on steroidogenesis and gene expression of CYP 11A, CYP 17, and CYP 19 were investigated using a porcine antral follicle culture model. Follicles were cultured with melatonin at doses of 10, 50, and 100 ng/mL in the presence and absence of an optimum dose of luteinizing hormone (LH) (100 ng/mL) for a period of 30 hours. It was found that melatonin stimulated progesterone production both in the presence and absence of LH. Androstenedione production was stimulated by melatonin at the highest dose of 100 ng/mL but melatonin had an inhibitory effect in the presence of LH. Estradiol production was not affected by melatonin alone, while in the presence of LH it showed a bimodal effect. Expression of genes for steroidogenic enzymes specific for the production of progesterone, androstenedione and estradiol (CYP 11A, CYP 17, and CYP 19, respectively) were also analyzed in the theca of follicles cultured with and without LH. Results showed an inhibition of CYP 11A and CYP 17 expression both in the presence and absence of LH. However, the expression of CYP 19 was not affected. Our results indicate that melatonin modulates ovarian theca cell steroidogenesis at the molecular level and this modulation may be mediated by its effects on the transcriptional activity of the steroidogenic enzymes.