[mRNA degradation in membrane-bound and free polyribosomes in rat liver cells after exposure to actinomycin D and cycloheximide].

Actinomycin D caused degradation of mRNA both in membrane-bound and in free polyribosomes from rat liver cells. The rate of mRNA destruction was distinctly higher in free polyribosomes, than in membrane-bound ones. Cycloheximide inhibited the mRNA destruction in both types of polyribosomes. At the same time, the stabilizing effect of cycloheximide on mRNA was less distinct in free polyribosomes. A decrease in specific radioactivity of mRNA from membrane-bound and free polyribosomes was observed after prolonged pretreatment with actinomycin D. The specific radioactivity of mRNA from polyribosomes of both types was not altered after simultaneous administration of actinomycin D and cycloheximide into rats. Occurence of two fractions of mRNA, dissimilar in stability, is possible both in membrane-bound and in free polyribosomes from rat liver cells.