REGULATION OF THE ACTIVITIES OF THE ENZYMES INVOLVED IN THE METABOLISM OF STEROID HORMONES IN RAT LIVER: THE EFFECT OF ADMINISTRATION OF ANTERIOR HYPOPHYSEAL HORMONES AND GONADOTROPHIN PREPARATIONS TO HYPOPHYSECTOMIZED RATS

Abstract

ABSTRACT A crude human hypophyseal extract (HE), as well as human growth hormone (GH), ovine prolactin (PRL) and commercial preparations of ACTH, TSH, pregnant mare's serum gonadotrophins (PMS) and chorionic gonadotrophin (CG) were tested for their ability to induce the activities of cytoplasmic 17β-hydroxysteroid dehydrogenase and microsomal Δ4-5α-hydrogenase and to repress the activities of microsomal 3α-and 3β-hydroxysteroid dehydrogenases in the liver of hypophysectomized rats. The activity of 17β-hydroxysteroid dehydrogenase was not affected by any of the administered hormones. For the other enzymes, only PRL was effective in causing changes in the activities; the repressive effect on 3α-hydroxysteroid dehydrogenase activity was highly significant (P < 0.001) These results indicate that PRL is involved in the regulation of at least some of the enzyme activities of hepatic steroid hormone metabolism.