Induction of methionine adenosyltranferase in rat liver by corticosteroids.

Abstract

SummaryThe induction of hepatic methionine adenosyltransferase by adrenal cortical hormones has been studied in adrenalectomized rats. Experiments with cortisol, cortisone, corticosterone, prednisolone, and triamcinolone revealed that triamcinolone was the most potent inducer of methionine adenosyltransferase activity. On the contrary, two mineral corticoids, aldosterone and deoxycorticosterone, and a biologically inactive isomer of cortisol, 11-epicortisol, were found to be ineffective in raising the hepatic level of this enzyme, indicating the specificity of the action of glucocorticoids in this respect. Actinomycin, puromycin, and cycloheximide, inhibitors of RNA or protein synthesis, largely blocked the glucocorticoid-induced increase in the enzyme, observed 12 hours after hormone administration. The results suggest that the changes in the hepatic levels of methionine adenosyltransferase brought about by glucocorticoids represent enzyme synthesis de novo probably involving enhanced DNA-directed RNA pr...