Ectopic pituitary transplants stimulate synthesis and release of follicle-stimulating hormone in golden hamsters

It was previously reported that PRL can stimulate FSH release in immature female rats and PRL-deficient male dwarf mice. We have examined the effects of PRL-producing ectopic pituitary grafts on plasma FSH and LH levels in adult male golden hamsters during exposure to both long (14 h of light, 10 h of darkness) and short (5 h of flight, 19 h of darkness) photoperiods. In both groups, the presence of one pituitary graft resulted in a significant elevation of pituitary and plasma FSH levels. Although there were no statistically significant changes in the concentration of LH in the pituitary or plasma of either group. LH values were more variable than FSH values, and these findings do not rule out an effect on LH. To determine whether the ability of ectopic pituitary grafts to stimulate FSH release depends on changes in testicular or adrenal function, additional experiments were done in castrated male hamsters, in castrated males given testosterone propionate, and in castrated adrenalectomized hamsters maintained with injections of cortisol. The results indicate that the increase in FSH release in engrafted animals does not depend on the testes or the adrenals, but can be prevented by exogenous cortisol. In adult female hamsters, pituitary grafts increased plasma LH levels above the concentrations observed in diestrous, proestrous, or pregnant controls, but did not alter plasma FSH levels. In contrast, in ovariectomized and ovariectomized-estradiol benzoate-treated animals, pituitary grafts increased plasma FSH levels without significantly affecting plasma LH. It is concluded that PRL-producing ectopic pituitary homografts significantly stimulate FSH synthesis and release in male golden hamsters, and that this effect is probably not mediated through the changes in gonadal or adrenal function.