ABSTRACT
In the male rat, androgens are involved in the feedback regulation of gonadotropin synthesis and secretion. Specific androgen-receptor blockade by the nonsteroidal antiandrogens, flutamide and Casodex, has proven to be a valid tool for studying androgen effects in vivo. The aim of the present study was to investigate the effect of antiandrogen administration at the pituitary level by evaluating the changes in gonadotropes through quantitative immunohistochemistry, and by comparing these alterations with the effect of androgen deprivation by castration either with or without subsequent androgen replacement. Male Sprague-Dawley rats (23 days old) were randomly divided into 5 groups for the following treatments: (a) controls; (b) flutamide-injected (10 mg/rat/day in a gelatin vehicle); (c) Casodex-injected (10 mg/rat/day in an oil vehicle); (d) castrated, and (e) castrated and dihydrotestosterone propionate-replaced (40 microg/rat/day in an oil vehicle). Groups were then sacrificed after 10 days of maintenance under each condition. Pituitaries were fixed in Bouin's fluid and embedded in paraffin. Serial sections (4 micrometer) were obtained at different levels and immunostained by means of the primary murine monoclonal antibodies anti-FSH and anti-LH and a peroxidase-mediated EnVision System (Dako). Measurements of volume density (VD) and individual mean cell area were made by means of an image-analysis system (Imaging Technology, Optimas). Serum FSH and LH levels were determined by radioimmunoassay (RIA). Serum gonadotropin levels, VD, and mean cell area increased significantly in the flutamide-treated, Casodex-treated, and castrated groups (p < 0.05). Androgen replacement in the castrated rats, however, reduced VD, mean cell area, and serum gonadotropins to levels comparable to those of controls. We conclude that either androgen blockade by antiandrogens or castration produce an enhancement in the gonadotrope cell population in prepubertal rats, as shown by an increase in both VD and mean cell area, as well as an elevation in FSH- and LH-immunoreactive cells. These observations correlate well with the changes found in the levels of circulating gonadotropins as measured by RIA.