Prolactin inhibition of estrogen production by cultured rat granulosa cells

Abstract

The effect of prolactin (PRL) treatment on estrogen production by rat granulosa cells was investigated in vitro. Immature, hypophysectomized, DES-treated rats were injected for 2 days with FSH to induce aromatase enzymes and receptors for PRL and LH. After FSH priming, the granulosa cells were cultured for 4 days in serum-free medium containing 10 −7 M androstenedione and purified FSH, LH and/or PRL. A dose-related inhibition of estrogen production from control cells was observed following PRL treatment in which 1 μg/ml of PRL inhibited estrogen formation by > 90%. In these same cultures, PRL caused a dose-related increase in progesterone and 20α-dihydroprogesterone secretion. Treatment with purified FSH or LH stimulated estrogen synthesis by 3–10-fold. Concomitant treatment with PRL suppressed the FSH- and LH-induced increases in estrogen production in a dose-dependent manner; 1 μg/ml PRL suppressed estrogen production by > 80% during days 2–4 of culture. In these same cultures, PRL did not alter the stimulatory effects of FSH and LH on progesterone and 20α-dihydroprogesterone production. These experiments demonstrate that PRL acts directly on rat granulosa cells in vitro to suppress basal and gonadotropin-induced increases in estrogen production.