Decreased protein synthesis by microsomes isolated from senescent rat liver

Protein synthesis as indicated by the incorporation of ¹⁴C-leucine or a mixture of ¹⁴C-labelled amino acids into cold TCA-insoluble material by liver microsomal fractions of mature adult (12 months) and old (20-31 months) female rats was investigated. A decreased amino acid incorporation into protein occurred in the cell-free system from senescent rat liver. Also, cross-mixing experiments indicate that the cytosol(105,000g supernatant) from senescent animals is inhibitory to protein synthesis with microsomes from 12 month old rats. The combination of cytosol from 12 month old animals and microsomes from senescent animals functioned most often like the senescent system.