[Stabilization of polyribosomal mRNA in rat liver cells under protein synthesis inhibition by cycloheximide].

It was found that in the course of centrifugation of the postmitochondrial fraction from rat liver in the sucrose concentration gradient, mRNA located in the EDTA-resistant structures sedimented together with polyribosomes. The same structures were detected in the polyribosomal fraction of liver cells after injection of ethionine to the animals. Centrifugation of polyribosomes through a layer of 2.0 M sucrose at 105 000 g for 4 hrs and subsequent centrifugation through a layer of 1.0 M sucrose resulted in the disappearance of the complexes from the polyribosomal fraction. Evidence for the absence of destruction of labelled polyribosomal mRNA in liver cells following the injection of cycloheximide were obtained. Actinomycin D also stabilized polyribosomal mRNA in liver cells, however, in a much lesser degree as compared to cycloheximide. Possible mechanisms of the stabilizing effects of cycloheximide and actinomycin D on polyribosomal mRNA in liver cells are discussed.