EFFECTS OF UNILATERAL ORCHIDECTOMY ON RAT EPIDIDYMAL DELTA-4-5-ALPHA-REDUCTASE AND 3-ALPHA-HYDROXYSTEROID DEHYDROGENASE

The effects of unilateral orchidectomy on the adult rat epididymal testosterone metabolizing enzyme, Δ4-5α-reductase and 3α-hydroxysteroid dehydrogenase, are investigated. Five weeks following unilateral orchidectomy, it is found that the activity of 3α-hydroxysteroid dehydrogenase per organ is not altered, whereas Δ4-5α-reductase activity by more than 80% on the side of the orchidectomy. Neither accessory sex tissue weights, ventral prostate and seminal vesicles, nor the concentrations of circulating testosterone, luteinizing hormone, follicle-stimulating hormone, or prolactin is altered by unilateral orchidectomy. These data indicate that epididymal 3α-hydroxysteroid dehydrogenase activity can be maintained by circulating androgens and that the major factor regulating Δ4-5α-reductase activity is not a substance secreted by the testes into the peripheral circulation. It is suggested that a substance directly secreted into the epididymis by the testis regulates epididymal Δ4-5α-reductase activity.