The Involvement of the Thyroid and Adrenal in the Regulation of Enzyme Activities of Hepatic and Renal Steroid Metabolism in the Rat

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Abstract
The response of some sexually differentiated steroid oxidoreductase activities of the liver (cytoplasmic 17.beta.-hydroxysteroid dehydrogenase [EC 1.1.1.63] and 5.beta.-reductase [EC 1.3.1.3], microsomal 3.alpha.-hydroxysteroid dehydrogenase [EC 1.1.1.50], 3.beta.-hydroxysteroid dehydrogenase [EC 1.1.1.51], 11.beta.-hydroxysteroid dehydrogenase [EC 1.1.1.146] and 5.alpha.-reductase [EC 1.3.1.4]) and of the kidney (cytoplasmic 3.alpha.-[hydroxysteroid dehydrogenase] and 20.alpha.-hydroxysteroid dehydrogenase [EC 1.1.1.49], microsomal 3.alpha.-, 11.beta.- [hydroxysteroid dehydrogenase] and 20.beta.-hydroxysteroid dehydrogenase [EC 1.1.1-]) to thyroidectomy or adrenalectomy was investigated in sexually mature rats. None of the renal enzyme activities was affected by either operation. All hepatic enzyme activities showed a reaction to thyroidectomy. The effects are surprisingly heterogeneous. With the exception of 3.alpha.-hydroxysteroid dehydrogenase activity, which decreases in both sexes, repression and induction of enzyme activities were sex-specific phenomena (e.g., 11.beta.-hydroxysteroid dehydrogenase: induction in females, repression in males; 5.alpha.-reductase: repression in females, no effect in males). Only 2 enzyme activities (3.alpha.- and 17.beta.-hydroxysteroid dehydrogenase) reacted to adrenalectomy. The reaction was uniform: both sexes showed a loss of activity. The regulation of the activities of enzymes of hepatic steroid metabolism is achieved through the complex interaction of hormones of different origins.