Differential inhibition of progesterone synthesis in bovine luteal cells by estrogens and androgens

We investigated the roles of estrogens and androgens in the progesterone biosynthesis of bovine luteal cells. The responsiveness of primary luteal cells to the stimulation of tropic agents was observed in a dose-dependent manner. Estrogens and androgens significantly inhibited tropic agent-induced progesterone secretions, but glucocorticoids did not, which indicated the inhibitions were specific. The failure of exogenous 8-Br-cAMP to prevent these inhibitions suggested that took place at the post-cAMP steps. The immunoblot showed that testosterone remarkably decreased the amount of induced P450scc protein after 6-hour treatment, yet 17β-estradiol did not. The 3β-HSD activity assays demonstrated that both 17β-estradiol and testosterone efficiently blocked induced 3β-HSD activities. Both inhibitory effects of E2 and T on progesterone synthesis were observed one hour after treatment and accompanied with suppressed 3β-HSD activities. This study presents that estrogens and androgens specifically inhibit bovine luteal function through different mechanisms.