ESTRADIOL-INDUCED CHANGES IN TSH-LIKE IMMUNOREACTIVITY OF PITUITARY-CELLS IN FEMALE RATS

Beta-thyrotropin (TSH)-producing cells in the pituitary pars distalis of female rats were studied using rabbit anti-rat beta-thyrotropin (TS H) serum and a peroxidase-antiperoxidase (PAP) immunohistochemical pro cedure. Animals were neonatally treated with 1 mg estradiol-dipropiona te (EDP) and sacrificed at different stages of development up to adult hood. Intact females of the corresponding age served as the controls. Morphometry and stereology were used to evaluate the changes in TSH-ce ll number and volume densities of the cells and nuclei. All morphometr ic parameters examined in estradiol-treated animals showed a significa nt decrease in comparison with immunoreactive TSH cells of age-matched controls. The most prominent EDP-induced changes were evident in peri pubertal 38-day-old rats, the number and volumetric densities of both TSH cells and their nuclei being reduced by about 90% compared to inta ct pituitary. This decrease in the number and volume densities of TSH cells in EDP-treated rats explicitly demonstrated that this hormone, a pplied neonatally, has an inhibitory effect on TSH-immunoreactive cell s up to adulthood, in accordance with our earlier data obtained by lig ht and electron microscopy.