Rat thymic dihydrotestosterone receptor: preparation, location and physiochemical properties

Castration in the male rat has been shown to produce enlargement of the thymus gland while treatment with dihydrotestosterone (DHT) results in a decrease in thymic size in these animals. To determine if these changes might be receptor mediated, thymus tissue from castrate male rats was removed and homogenized in buffer and centrifuged to produce cytosol. By Scatchard plot analysis, it was shown that a specific DHT receptor was present at a concentration of 0.24 +/- 0.02 pmoles/g tissue and it possessed a KA of 2.51 +/- 0.45 x 10(9)M-1. This thymic DHT receptor sedimented on 5--20% sucrose gradients in the 8s region. By competition analysis it was found that testosterone only partially competed (25%) for this receptor, with virtually no binding noted for estradiol, progesterone, and cortisol. The receptor was found to be localized in the reticuloepithelial matrix of the thymus and was not present in the thymic lymphocyte fraction.