Thus, granulosa-derived activin and fol-listatin may have selective paracrine modulatory roles on thecal androgen synthesis and, in turn, affect estradiol production by the granulosa cells. It is not known yet whether higher estradiol production by the granulosa cells caused them to express more follistatin or vice versa. Although existence of a cause-and-effect relationship is speculative at this stage, temporal relationships discovered during this study provide a basis for the postulate that greater expression of follistatin promotes follicle dominance and lesser expression will lead to continued growth of the subordinates. buy ventolin inhalers
Our results demonstrated stage-specific changes in the amount of follistatin in the granulosa cells of dominant follicles. In contrast, the concentration of follistatin in human follicular fluid did not vary among healthy, atretic, and preovulatory follicles in women undergoing in vitro fertilization, nor were differences found in abnormal follicles obtained from patients with polycystic ovarian syndrome. Differences in results may be attributed to species differences or to the possibility that the amount of follistatin detected in the follicular fluid may not truly reflect the amount of follistatin produced by granulosa cells. In this regard, follistatin has a high affinity for sulfated proteoglycans, particularly heparin sulfate located in follicular fluid and on the surface of granulosa cells. In addition, the localization of follistatin on the surface of cells is not necessarily correlated with the production of follistatin by the same cell type. However, in the present study, we observed specific perinuclear localization of follistatin with aggregates close to the nucleus of both granulosa and luteal cells, presumably in the Golgi region of the cells.