Proliferative and steroidogenic effects of follicle-stimulating hormone during chick embryo gonadal development

The aim of this study was to evaluate the in vitro effect of human follicle-stimulating hormone (hFSH) on cellular proliferation and steroid hormone secretion in the left ovary, the right ovary, and the testis of the chick embryo. Gonads from 8- to 18-day-old chick embryo were cultured in a defined medium during 60 h under basal and hFSH-stimulated conditions (0.5 IU/ml of culture medium). At the end of the culture, the incorporation of ¿(3)Hthymidine and the total number of cells were measured to estimate gonadal cell proliferation. The secretion of 17beta-estradiol and testosterone in the culture medium was radioimmunologically assayed in order to evaluate the steroidogenic function of the cultured gonadal cells. The response to hFSH stimulation was observed in the left ovary, the right ovary, and the testis from the 8-day-old chick embryo. In the left ovary, cellular proliferation was not augmented by hFSH in the 8-, 10-, and 13-day-old chick embryo; meanwhile, the proliferative stimulus of hFSH was observed in the 15- and 18-day-old embryos. In the same ovary, 17beta-estradiol and testosterone secretion were stimulated after hFSH treatment at all evaluated stages (8-18 days of chick embryo development). In the right ovary, an increment in proliferation and steroidogenesis was induced by hFSH in the 8-, 10-, and 13-day-old chick embryo. Afterward, the right gonad did not respond to hFSH. Testis cells displayed hFSH response as an increment in cell proliferation at all embryonic ages (8-18 days of chick embryo development). There was a transient lack of response to hFSH in testosterone secretion at 10 and 13 days of development. The in vitro effect of hFSH on cell proliferation and steroid hormone secretion changed in the ovary and the testis according to the age of the embryo. These changes could be attributed to the growth of the left ovary and the testis and the regression of the right ovary. Probably, paracrine factors modulated the gonadotropin effect on the target cells during embryonic development of chick embryo gonads.