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

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Abstract
A crude human hypophyseal extract (HE), and human growth hormone (GH), ovine prolactin (PRL) and commercial preparations of ACTH, thyrotropin, pregnant mare''s serum gonadotropins and chorionic gonadotropin were tested for their ability to induce the activities of cytoplasmic 17.beta.-hydroxysteroid dehydrogenase and microsomal .DELTA.4-5.alpha.-hydrogenase and to repress the activities of microsomal 3.alpha.- and 3.beta.-hydroxysteroid dehydrogenases in the liver of hypophysectomized rats. The activity of 17.beta.-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 3.alpha.-hydroxysteroid dehydrogenase activity was highly significant (P < 0.001). PRL is involved in the regulation of at least some of the enzyme activities of hepatic steroid hormone metabolism.

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