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

Abstract

The metabolism of testosterone and 5α-dihydrotestosterone has been studied in vitro in preputial glands of posterior hypophysectomized, totally hypophysectomized and control sham-operated rats. The level of C19 steroid 5α-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 5α-reductase and hence that the combined synergistic action of testosterone and α-melanocyte-stimulating hormone (α-MSH) on preputial gland activity was unlikely to be due to an α-MSH-mediated restoration of 5α-reductase levels in hypophysectomized rats. Levels of 3α-and 3β-hydroxysteroid dehydrogenase but not of 17β-hydroxysteroid dehydrogenase appeared to be altered by hypophysectomy.