Rate of RNA turnover in rat liver in relation to intake of protein

Abstract

The effect of dietary intake of protein on the turnover of liver RNA has been measured in rats by observing the rate of loss of label from liver ribosomal RNA over a period of several days after injection of 3H-labeled orotic acid. Rats receiving a normal intake of protein showed fractional rates of RNA synthesis and degradation of about 20–25% daily. When rats were fed a diet free of protein, RNA breakdown was at first accelerated to over 40% per day. However, after 2 days on the protein-free diet the fractional rate of degradation fell to about 15% daily, and the rate of RNA synthesis to an even lower level, so that animals on this diet showed a continuous reduction in the RNA content of their livers. On the basis of the present and earlier studies, it is suggested that RNA turnover is regulated through changes in the population of free ribosomal subunits in the liver cytoplasm, the abundance of subunits being affected by amino acid supply.