Changes in TSH-immunoreactivity in the pars tuberalis and pars distalis of the fetal rat hypophysis following maternal administration of propylthiouracil and thyroxine.

The pars tuberalis (pt) of the adenohypophysis is unique in its close spatial relationship to the neurohemal contact area of the median eminence. The morphology of pt-specific secretory cells does not resemble cell types of the pars distalis (pd); the functional role of these cells within the endocrine system is still unknown. One group of young mature female Wistar rats received propylthiouracil (PTU), a second group thyroxine (T4) (10 mg/l each in drinking water) from about 3 weeks prior to the expected pregnancy and throughout the experiment. On gestation day 20, the fetuses were obtained by laparatomy. Serial sections from the rostral portion of the pt and from the pd were immunostained using the peroxidase-antiperoxidase method. TSH concentrations were determined by RIA in serum and pituitaries; T4 was measured in serum. An antiserum against rat (r) TSH revealed a moderate positive reaction of nearly all cells of the pt in the control group. In both experimental groups the pt-specific cells showed weak or no immunoreactivity. Sections of all groups were negative with anti(r)-LH, -GH, -PRL. In contrast to controls, only a few immature TSH-cells could be found in sections of the pd in the T4-group, while concentrations of TSH in blood and hypophysis were very low. TSH-cells in the PTU-group were enlarged and less intensely stained. TSH-concentrations were decreased in the hypophysis, blood levels were elevated. All sections of the pd-specific cell populations showed positive immunoreactions with anti-r)-LH, -GH, -PRL.(ABSTRACT TRUNCATED AT 250 WORDS)