Seasonal fluctuations of androgen-binding activity in the testis of the frog, Rana esculenta".

An androgen-binding activity has been identified in nuclear extracts of the testis of the frog, Rana esculenta. A single class of high affinity (I& = 2.5 * 0.6 x 10m9M), low-capacity binding sites was found. The binding was specific for androgens; 17@estradiol displaced [3H]testosterone with an ID,, of 0.1 PM. Cytosolic binding activity has a low affinity and a high capacity and lacks specificity. The seasonal fluctuations in binding capacity did not correlate with the androgen peaks in plasma and testes between February and June and in September; periods coinciding with the resumption of spermatogenesis and the development of spermatids, respectively. The present data strongly support androgenic control of intratesticular function in vertebrates generally.