In vitro measurement of cytosol and cell nuclear androgen receptors in male rat brain and pituitary.

An in vitro assay procedure is described for measuring androgen receptor binding in cytosol and cell nuclei of brain and pituitary tissue using [3H]R1881 as ligand. The cell nuclear assay uses the exchange method, which permits assessment of endogenous occupancy of androgen receptors in brain and pituitary. Competition and saturation analysis indicated that [3H]R1881 binding has the specificity and nanomolar affinity expected of an androgen receptor. Moreover, we demonstrated that androgen receptor binding predominated in cytosol from castrated rats and in cell nuclei of male rats treated in vivo with testosterone. Furthermore, as expected, testicular feminized male rats showed low levels of putative androgen receptors in both cytosol and cell nuclei.