Goat ovarian follicles express different levels of mRNA for inhibin-ßA subunit and activin-A stimulates secondary follicle growth in vitro

This study investigated the levels of messenger ribonucleic acids (mRNA) for inhibin-sA subunit in goat primordial, primary and secondary follicles, as well as in cumulus-oocyte complexes (COCs) and mural granulosa / theca cells of antral follicles. The effects of activin-A (100ng mL-1) and/or follicle stimulating hormone (FSH, 50ng mL-1) on growth and expression of mRNA for activin-A and FSH receptor (FSH-R) in secondary follicles cultured for six days were evaluated. The data showed that the expression of inhibin-sA is lower in secondary follicles than in primary follicles and is higher in large antral follicles than in small antral follicles. After culture, activin-A and/or FSH promoted growth of secondary follicles, while FSH increased the levels of mRNA for inhibin-sA, and activin-A increased the levels of FSH-R mRNA. In conclusion, mRNA for inhibin-sA is expressed at different levels in pre-antral and antral follicles and activin-A acts as a stimulator of the FSH-R expression in goat follicles. On its turn, the expression of inhibin-sA is stimulated by FSH, which together with activin-A promotes secondary follicle growth in-vitro.