Effect of castration and steroid replacement on immunoreactive luteinizing hormone cells in the pars tuberalis of the rat.

The response of LH cells in the pars tuberalis of the rat hypophysis to castration alone or castration and subsequent administration of testosterone propionate or estradiol benzoate was studied. To accomplish this, LH cells were labeled by the peroxidase-antiperoxidase immunocytochemical method, with use of an antiserum generated against hCG. LH cells were detected in the caudal region of the pars tuberalis of all intact control animals studied. After castration, LH cells in both the pars distalis and pars tuberalis showed similar degrees of hypertrophy and hyperplasia. This response was inhibited by either testosterone propionate or estradiol benzoate in the pars distalis as well as in the pars tuberalis. These results indicate that LH cells in the pars tuberalis, in addition to those in the pars distalis, are responsive to fluctuations in circulating steroid hormone levels and that the pars tuberalis may contribute to the overall secretion of gonadotropin by the adenohypophysis.