A comparison of protein synthesis by liver parenchymal cells isolated from Fischer F344 rats of various ages.

Rates of protein synthesis by intact liver parenchymal cells isolated from male Fischer F344 rats ranging in age from 2.5 to 30 months were determined by measuring the incorporation of [3H] valine into acid-insoluble material and the specific activity of the extracellular valine. The rate of protein synthesis decreased 44% from 2.5 to 18 months and then increased slightly (18%) from 18 to 30 months. There was no dramatic change in the types of proteins synthesized by isolated liver parenchymal cells isolated from 2- or 18-month-old rats as determined by SDS-polyacrylamide gel electrophoresis. The ribosomal-transit time by liver parenchymal cells isolated from 18-month-old rats was 60% higher than the ribosomal-transit time of liver parenchymal cells isolated from 4-month-old rats. The fidelity of protein synthesis by parenchymal cells isolated from 4- and 18-month old rats was compared by measuring the incorporation of p-fluorophenyl alanine (an analogue of phenylalanine) into acid-insoluble material. Although protein synthesis decreased significantly from 4 to 18 months, the fidelity of protein synthesis remained constant.