Concentration of Testosterone and Dihydrotestosterone in Subcellular Fractions of Liver, Kidney, Prostate, and Muscle in the Male Dog

Testosterone-1,2-3H was infused intravenously at a constant rate to four adult male dogs over a period of 120 min, at which time the plasma concentration of testosterone-3H reached a plateau indicating a state of equilibrium in all body compartments. The specific activity of plasma testosterone at the end of the constant infusion was determined. Parts of the liver, kidney, striated muscle, and the prostate were removed, homogenized, and fractionated by ultracentrifugation. The concentration (per 100 mg of protein) of testosterone and dihydrotestosterone in each fraction was then calculated from the concentration of testosterone-3H and dihydrotestosterone-3H divided by the specific activity of the plasma testosterone-3H. Of all the organs, the prostate had the highest concentration of testosterone and dihydrotestosterone, and the subcellular fraction with the highest concentration of testosterone and dihydrotestosterone was the microsomal fraction of the prostate. Furthermore, the concentration of dihydrotestosterone exceeded the concentration of testosterone only in that fraction. The concentration of dihydrotestosterone in plasma was below the sensitivity of the method employed. The data are interpreted to indicate the presence of a material with a high affinity for testosterone and dihydrotestosterone in the cells of the prostate, most markedly at the microsomal fraction. The higher concentration of dihydrotestosterone in this fraction may be interpreted as suggesting that this is the site of conversion of testosterone to dihydrotestosterone.