Mechanism of action of alpha-melanocyte-stimulating hormone in rat preputial glands: the role of androgen metabolism.

The metabolism of testosterone and 5 alpha-dihydrotestosterone has been studied in vitro in preputial glands of posterior hypophysectomized, totally hypophysectomized and control sham-operated rats. The level of C19 steroid 5 alpha-reductase activity/unit of preputial gland DNA did not fall after removal of the neurointermediate lobe and rose after total hypophysectomy. It was concluded from this that the androgen unresponsiveness of the preputial glands of hypophysectomized rats was not due to a near-total lack of 5 alpha-reductase and hence that the combined synergistic action of testosterone and alpha-melanocyte-stimulating hormone (alpha-MSH) on preputial gland activity was unlikely to be due to an alpha-MSH-mediated restoration of 5 alpha-reductase levels in hypophysectomized rats. Levels of 3 alpha and 3 beta-hydroxysteroid dehydrogenase but not of 17 beta-hydroxysteroid dehydrogenase appeared to be altered by hypophysectomy.