Binding of estradiol and 5 alpha-androstane-3 beta-17 beta-diol by the male rat enriched gonadotrope cells.

Dispersed pituitary cells from 42-day old male rats were separated using centrifugal elutriation. Based on LH and PRL cellular contents, fractionated cells were pooled into two fractions: "Lactotrope++ population" and "gonadotrope++ population". Estradiol and 5 alpha-androstane-3 beta, 17 beta-diol binding was measured in these fractions. Results revealed that: (1) The steroid receptors are not destroyed by cell dispersion and elutriation. (2) The estradiol receptor content is higher in gonadotrope++ cells than in lactotrope++ cells. (3) The number of binding sites for the two steroids changes in the different fractions: whereas it is exactly similar in "lactotrope++ population", it is much higher for estradiol than for 5 alpha-androstane-3 beta, 17 beta-diol in "gonadotrope++ population". These results suggest two different species--or conformations--of receptor binding sites for estradiol in the male rat pituitary; the first one could link both steroids, the second one would be specific for estradiol.