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.

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 17 beta-hydroxysteroid dehydrogenase and microsomal delta 4-5alpha-hydrogenase and to repress the activities of microsomal 3alpha- and 3beta-hydroxysteroid dehydrogenases in the liver of hypophysectomized rats. The activity of 17beta-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 3alpha-hydroxysteroid dehydrogenase activity was highly significant (P less than 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.