Effects of prolactin on steroidogenesis by human luteinized granulosa cells

The role of prolactin (PRL) in the regulation of human ovarian function is poorly understood, and reported findings are often contradictory. We have evaluated the effects of several doses of PRL on the secretion of progesterone (P) and estradiol (E2) by human granulosa cells from preovulatory follicles of gonadotropin-stimulated women. The effects of PRL were also evaluated when androstenedione (delta 4 A) was added to the cultured cells. Our findings show that the human granulosa lutein cells retain their ability to secrete large amounts of P and lesser quantities of E2 for a prolonged period in culture. E2, but not P, secretion was stimulated by the presence of delta 4 A. PRL in low doses (25 and 50 ng/ml) did not alter the secretion of either E2 or P. In contrast, high doses of PRL (100 and 1000 ng/ml) resulted in a significant suppression of E2 secretion. P secretion was inhibited only by the highest dose (1000 ng/ml) of PRL. We conclude that steroidogenesis by the granulosa lutein cells of preovulatory human follicles is probably not influenced by the quantities of PRL that are normally present in the blood or follicular fluid. Higher doses, however, may suppress production of E2 and P.