These results suggest that the effects of PRL on ovarian cells may largely depend on the differentiation of PRL receptors. Using a eCG-primed mouse granulosa cell culture model, we have demonstrated that PRL significantly enhances FSH- and LH-induced progesterone production, while it inhibits aromatase activity. In vivo experiments also showed that PRL inhibits hCG-induced ovulation in mice by decreasing ovarian PA activity and serum estrogen concentrations. Both FSH and LH have been demonstrated to induce tPA mRNA and activity in cultured granulosa cells. buy ortho tri-cyclen
This study further provided evidence to show that tPA activity induced by LH is dramatically inhibited by the presence of PRL in a dose-dependent manner This result is consistent with the previous reports that PRL significantly decreased hCG-in-duced ovulation by inhibiting ovarian PA activity in vitro and in vivo. PRL was also demonstrated to inhibit hCG-induced ovulation in mice. Both in vivo and in vitro experiments showed that PRL inhibition of gonadotropin-induced tPA expression was regulated by decreasing tPA mRNA synthesis on the one hand, and by neutralizing PA activity by the increased PAI-I molecules on the other. This suggestion is further supported by the fact that the decrease in tPA activity by PRL is correlated with a formation of PA-PAI-I complexes.