Differential Distribution of Androgen and Estrogen Receptors in Rat Pituitary Cell Populations Separated by Centrifugal Elutriation

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Abstract
The distribution of 5.alpha.-dihydrotestosterone (DHT)-binding sites within specific pituitary cell populations, as compared with the estradiol (E2)-binding sites distribution, could be estimated after gonadotrope cell enrichment. Centrifugal elutriation allowed the purification of large gonadotropes from 42-day-old male rat pituitaries; this population contained 5.3 .+-. 1.0% of the cells, 54 .+-. 3% of the LH [luteinizing hormone] and < 5% of PRL [prolactin]. A gonadotrope-depleted fraction was also defined that contained more than 92% of the total PRL and was thus called the lactotrope population though it still contained small gonadotropes and most somatotropes. DHT and E2 receptors were quantified by multidose saturation analysis. The association constants (Ka) ranged from 0.2-0.5 .times. 109 M-1 both for E2 and DHT independent of the cell population. The binding of DHT was mainly observed in the gonadotropes (50-100 fmol/106 cells), while it was very low in the other cells (0.9-3 fmol/106 cells). E2-binding sites measured within the same cell populations showed a broader distribution than DHT-binding sites. Whereas the ratio of binding DHT/E2 averaged 0.86 .+-. 0.01 in the gonadotropes, it reached only 0.35 .+-. 0.07 in the lactotropes. Thus, using enriched cell populations, these results demonstrate for the 1st time a quantitative selective distribution of androgen-binding sites as compared with the estrogen sites.