MELATONIN AND STEROIDS IN HUMAN PREOVULATORY FOLLICULAR-FLUID - SEASONAL-VARIATIONS AND GRANULOSA-CELL STEROID-PRODUCTION

Follicular fluid samples were obtained from the largest preovulatory f ollicle of 120 women undergoing in-vitro fertilization and were examin ed for melatonin by enzyme-linked immunosorbent assay and the steroids oestradiol and progesterone by radioimmunoassay, The concentrations ( mean +/- SE) of melatonin (213.4 +/- 18.9 pmol/I) and progesterone (20 .1 +/- 1.1 mu mol/l) in follicular fluid during the autumn and winter (dark) months were significantly higher than during the spring and sum mer (light) months, melatonin (138.4 +/- 12.5 pmol/I) and progesterone (11.6 +/- 0.8 mu mol/I). By contrast, oestradiol concentrations were significantly lower during the dark months than during the light month s (264.7 +/- 44.1 and 661.8 +/- 55.1 nmol/l respectively), There was a positive correlation between follicular fluid melatonin and progester one concentrations (r = 0.271, P < 0.05, n = 120) and a negative relat ionship between melatonin and oestradiol (r = -0.254, P < 0.05, n = 12 0), The effects of melatonin alone and in combination with human chori onic gonadotrophin (HCG) or follicle stimulating hormone (FSH) on ster oidogenesis by human granulosa cell culture were also investigated. Me latonin had minimal effects on oestradiol or progesterone production b y granulosa cells, Interestingly, the oestradiol response in culture a ppeared to be different according to the time of the year when harvest ed, During the light period oestradiol production was enhanced, Melato nin also synergized with HCG in increasing progesterone production on days 6 and 7 after treatment during both light and dark periods, FSH s timulated oestradiol production by the cells on day 2 of culture, Mela tonin had no effect on FSH stimulation of oestradiol production, The r esults of this study suggest that melatonin may be involved in the reg ulation of steroidogenesis by the human ovaries.