The hormonal control of Sertoli cell function will be investigated using androgen binding protein as an indicator. Emphasis will be placed on the interrelation between the actions of androgens and FSH. Measurements of androgens and androgen binding protein will be made in monkey rete testis fluid. Intracellular andorgen receptors will be identified and characterized in monkey testis and epididymis. Biochemical and autoradiographic studies will be carried out to localize androgen receptors in different target cells of the testis. Androgen receptors will be further characterized with respect to interaction with target cell nuclei.