Androgen directs apparent cytoplasmic and nuclear distribution of rat cardiovascular androgen receptors

Abstract

We used either the synthetic androgen R1881 (methyltrienolone) or 5 alpha-dihydrotestosterone (5 alpha-DHT) to characterize androgen receptors in rat aortic and myocardial cytoplasmic and nuclear preparations. Relative steroid specificity studies established that only androgens were effective inhibitors of R1881 (cytoplasmic) or 5 alpha-DHT (nuclear) binding to aortic and myocardial androgen receptors, whereas estrogens, progestins, and cortisol were ineffective inhibitors. Low ionic strength sucrose density gradient centrifugation analyses showed that androgen receptors in aortic and myocardial cytoplasmic preparations migrated as macromolecules with sedimentation coefficients of 8 to 9S, whereas androgen receptors in aortic and myocardial nuclear preparations migrated as macromolecules with sedimentation coefficients of 4 to 5S (high ionic strength buffer). Saturation analyses established that aortic and myocardial cytoplasmic preparations from intact, untreated young mature female rats contained 45.8 +/- 9.7 (mean +/- SD) and 63.3 +/- 20.7 fmol androgen receptor/mg DNA, respectively. The respective R1881 dissociation constants were 0.60 and 0.32 nM. Androgen receptors could not be demonstrated in nuclear preparations from the cardiovasculature of intact females. Testosterone injection of intact young mature female rats caused apparent depletion of androgen receptors in aortic and myocardial cytoplasmic preparations and resulted in concomitant appearance of 57.1 +/- 22.2 and 52.3 +/- 21.5 fmol receptor/mg DNA in the corresponding nuclear preparations. The respective 5 alpha-DHT dissociation constants were 4.46 and 1.63 nM. The ability of testosterone to affect apparent intracellular distribution of cardiovascular androgen receptors suggests that the receptors are physiologically functional and indicates that androgen may directly regulate cardiovascular cell function.