Effect of cortisol and estradiol on tissue binding of testosterone

¹ Department of Medicine, Harvard Medical School; and Peter Bent Brigham Hospital, Boston, Massachusetts

Simultaneous administration of cortisol and testosterone-4-C¹⁴ to the rat results in a decrease in the concentration of radioactivity in several tissues similar to that observed when the testosterone-4-C¹⁴ is diluted with an equal amount of nonlabeled testosterone. Estradiol, when given simultaneously with the labeled testosterone, did not show the same effect. These findings are interpreted that testosterone and cortisol compete for the same sites of binding in the tissues examined. The subcellular distribution in muscle, kidney, and liver following intravenous injection was almost identical to that found following in vitro addition to the tissues.