Abstract
We evaluated the effect of transferrin on the regulation of granulosa cell function in humans by evaluating the production of progesterone (P) in the pre-ovulatory phase in vivo, and in cultured porcine granulosa cells in vitro. Twenty-five women treated for in vitro fertilization and embryo transfer had their serum levels of 17Β-estradiol (E2) and P determined on the day of administration of human chorionic gonadotropin. Transferrin concentrations were also determined in ovarian follicular fluid. In an in vitro study, porcine granulosa cells were cultured in the presence of follicle-stimulating hormone (FSH) and transferrin. Serum levels of P showed a significant negative correlation with those of transferrin (r = -0.53, p < 0.01), whereas serum levels of E2 did not (r = 0.14). When the subjects were divided into two groups by serum P concentration (low P < 1 ng/ml, high P ≥ 1 ng/ml) serum concentrations of transferrin were significantly increased in the group with the low versus the high level of p (p < 0.01). Production of P by porcine granulosa cells was suppressed by transferrin in the presence of various concentrations of FSH. Increasing the dose of transferrin significantly suppressed the production of P by those cells in a dose-dependent fashion. The production of P during the preovulatory phase may be suppressed by transferrin in the granulosa cells.