The aim of the present study was to evaluate the effect of
hypophysectomy on cell proliferation in the left ovary and the left testis of 8- to 14-day-old chick embryos.
Hypophysectomy was performed by the partial
decapitation technique. At 44-46 h of incubation, chick embryo heads were sectioned at the mesencephalic level and the prosencephalic region removed. Embryos were further incubated until 8-14 days of development. Cell division was evaluated by
bromodeoxyuridine (
BrdU) incorporation and by counting the total number of somatic and germ cells in the gonads. The ovary displayed an exponential increase in the number of somatic and germ cells and a higher rate of
BrdU incorporation compared to the testis.
BrdU incorporation was reduced in the ovary of hypophysectomized embryos at 9-14 days of incubation, while in the testis, the reduction was significant at 14 days of development. Changes in the total number of somatic and germ cells further suggest that the absence of hypophysis affects the growth of the ovary earlier than the growth of the testis. Reduction in the number of somatic and germ cells after
hypophysectomy in the ovary was reversed by a hypophyseal graft on the chorioallantoic membrane. The adenohypophysis regulates, probably through gonadotropic
hormones, proliferation of somatic and germ cells in the gonads during chick embryo development.