DIRECT EFFECTS OF ESTRADIOL AND TAMOXIFEN ON GENE EXPRESSIONS OF INHIBIN ALPHA-SUBUNIT AND BETA-A-SUBUNIT IN RAT GRANULOSA-CELLS IN-VITRO

To analyze direct effects of estrogen on gene expressions of inhibin s ubunits in vitro, the mRNA levels of inhibin alpha- and beta A-subunit s were measured in rat granulosa cells cultured with FSH or estradiol. Through the culture process of the granulosa cells with serum-free me dium, both the alpha- and beta A subunit mRNAs decreased, and were par tially increased again by adding FSH to the culture medium. To examine whether these FSH effects are mediated via estrogen production, estra diol or tamoxifen was added to the cultured granulosa cells. After 36- h culture with estradiol, the inhibin alpha-subunit decreased but the inhibin beta A-subunit increased, in a dose-responsive manner. Tamoxif en showed completely opposite effects to estradiol, and a combination of estradiol and tamoxifen resulted in similar levels of inhibin-alpha and -beta A mRNAs to the control. These results indicate that estroge n would by a certain pathway affect gene expressions of the inhibin su bunits in the rat granulosa cells, and may regulate the production of inhibin and activin through the paracrine system.