Effects of androgens and antiandrogens on the quantitative immunohistochemistry of gonadotrope cells in prepubertal male rats

In the male rat, androgens are involved in the feedback regulation of gonad otropin synthesis and secretion. Specific androgen-receptor blockade by the nonsteroidal antiandrogens, flutamide and Casodex, has proven to be a vali d tool for studying androgen effects in vivo. The aim of the present study was to investigate the effect of antiandrogen administration at the pituita ry level by evaluating the changes in gonadotropes through quantitative imm unohistochemistry, and by comparing these alterations with the effect of an drogen 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-inj ected (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 dihydrotestos terone propionate-replaced (40 mu g/rat/day in an oil vehicle). Groups were then sacrificed after 10 days of maintenance under each condition. Pituita ries were fixed in Bouin's fluid and embedded in paraffin. Serial sections (4 mu m) were obtained at different levels and immunostained by means of th e primary murine monoclonal antibodies anti-FSH and anti-LH and a peroxidas e-mediated EnVision System (Dako). Measurements of volume density (VD) and individual mean cell area were made by means of an image-analysis system (I maging Technology, Optimas). Serum FSH and LH levels were determined by rad ioimmunoassay (RIA). Serum gonadotropin levels, VD, and mean cell area incr eased significantly in the flutamide-treated, Casodex-treated, and castrate d groups (p < 0.05). Androgen replacement in the castrated rats, however, r educed VD, mean cell area, and serum gonadotropins to levels comparable to those of controls. We conclude that either androgen blockade by antiandroge ns 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 observa tions correlate well with the changes found in the levels of circulating go nadotropins as measured by RIA.