Hormones and liver cytoplasm. 4. Ribonucleotides, ribonucleic acid synthesis and protein synthesis after adrenalectomy

Abstract

Adrenalectomy leads eventually to a marked decrease (exceeding 50%) in the levels, in rat liver, of uridine 5[image]-diphosphate (-pyrophosphate) and its glucuronic acid derivative, and of uridine triphosphate; also to some decrease in uridine diphosphate acetylglucosamine and possibly in uridine diphosphate glucose, but not in liver nucleotides in general. Microsomal and supernatant fractions were isolated from liver at intervals after the injection of labeled orotic acid. Decrease in the labeling of the ribonucleic acid of the microsomal fraction after adrenalectomy and its increase in the supernatant fraction are compatible with the possibility that ribonucleic acid in the supernatant fraction is a precursor of microsomal ribonucleic acid. Supernatant fractions containing labeled ribonucleic acid were fractionated by several methods, two of which indicated heterogeneity with respect to the time course of labeling. However, the labeling of the different subfractions was equally affected by adrenalectomy. The labeling of nuclear and acid-soluble fractions, and of uridine nucleotides separated from the latter, showed no increase after adrenalectomy. The labeling of microsomal ribonucleic acid, with leucine as precursor, and the amount of microsomal protein were undiminished 3 days after adrenalectomy but decreased thereafter. The increase in the labeling of supernatant-fraction ribonucleic acid was apparent 3 days after adrenalectomy, as was also a rise in the amount of this ribonucleic acid which evidently occurred because of an increase in synthesis, rather than a decrease in catabolism.