Biochemical Characterization of Myocardial Cytoplasmic Androgen Receptors

Using the synthetic androtfen R1881 (17/S-hydroxy-17a-methyl-estra-4,9,ll-trien-3-one) as probe, we identified cytoplasmic androgen receptors in baboon myocardium. The relative binding affinity of selected steroids for the androgen receptor was R1881, 100%; Sa-dihydrotestosterone, 32.8%; testosterone, 29.6%, progesterone, 7.2%; R5020, 1.0%; and estradiol-17/3, 5.8%. The androgen receptor migrated on low ionic strength linear sucrose density gradients as a macromolecule with a sedimentation coefficient of 8.5S. Saturation analysis performed at 2°C (available sites) showed that the androgen receptor content of baboon myocardial cytoplasmic extracts was 9.9 i 1.4 fmol/mg protein and that the dissociation constant for R1681 was 1.16 ± 0.30 run. These cytoplasmic androgen receptors are indicated to be physiologically functional by previous autoradiographic studies (McGill et aL, 1980; McGill and Sheridan, 1981) that showed localization of radloisotope In nuclei of myocardial fibers following injection of baboons with 5a-dihydrotestosterone. Ore Res 49: 1010-1016, 1881