ACTIVIN INHIBITION OF ESTRADIOL AND PROGESTERONE PRODUCTION IN PORCINE GRANULOSA-CELLS

Two studies evaluated the influence of activin on steroidogenesis in c ultured porcine granulosa cells obtained at various stages of differen tiation. In granulosa cells isolated from 1- to 3-mm follicles, obtain ed at random stages of the estrous cycle, treatment with activin or tr ansforming growth factor beta (TGF beta) decreased progesterone produc tion during the first 48 h of culture, but neither had an effect on es tradiol production. One-half of these cells received FSH treatment at 48 h, and at 96 and 144 h of culture FSH increased estradiol and proge sterone production. Activin or TGF beta reduced, in a dose-dependent m anner, both basal and FSH-stimulated production of both steroids. In t he second study, granulosa cells were obtained during follicular growt h associated with weaning and were separated into two subpopulations ( weakly associated [WA] and tightly bound [TB]). Estradiol production i n culture increased with time after weaning. Tightly bound cells produ ced more estradiol than WA cells and maintained FSH-stimulated estradi ol production, whereas production of progesterone increased in both ce ll types after treatment with FSH. Activin depressed FSH-stimulated es tradiol production in TB cells and depressed FSH-stimulated progestero ne production in both cell types. These results clearly indicate that activin depresses in vitro steroidogenesis by granulosa. cells from an tral, porcine follicles; thus, activin may participate in atresia of a ntral follicles of this species.