Abstract
Hemisected pituitaries of cods were incubated in vitro at 41°C for 3hr with and without testosterone. progesterone, or estradiol-17β (1 and 10ng/ml), and media were assayed for the gonadotropic activity by using a bioassay method based on 32P-uptake by chick testes. The media in which the pituitary halves were incubated with testosterone (10ng/ml) showed a greater gonadotropic activity than those in which the other pituitary halves were incubated without testosterone. Incubations with progesterone or estradiol-17β did not result in a change in the gonadotropic activity of the media. When pituitaries were divided into cephalic and caudal lobes, and each lobe was hemisected and incubated in the same way, the incubation of the cephalic lobes with testosterone (5 and 10ng/ml) resulted in the increase in the gonadotropic activity of the media, while the incubation of the caudal lobes did not result in the increase. Synthetic GnRH (250 and 500ng/ml) caused the increase in the gonadotropic activity of the media in both incubations of the cephalic lobes and of the caudal lobes. The results suggest that testosterone acts on the pituitary and leads to the release of gonadotropins, and that the responsiveness of the pituitary to testosterone differs between the cephalic and caudal lobes.
