Effect of Protein Intake on the Ribonucleic Acid of Liver Cell Sap

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Abstract
The RNA content and amino acid-incorporating capacity of rat liver cell sap was studied with 3 groups of animals, (a) rats that had been fed a protein-free diet, (b) rats in the post-absorptive state after receiving a diet of adequate protein content, and (c) rats actively absorbing amino acids from a recent meal of protein. Cell sap prepared from animals of the second dietary group had a higher RNA content than that from either of the other groups, but showed a reduced capacity to incorporate leucine-C14 in relation to the amount of RNA present. By centrifugation for 3 hours at 105,000 × g, a precipitate (post-microsomal fraction) was isolated from the cell sap. The effect of protein intake on the RNA content and amino acid-incorporating capacity of cell sap was shown to be due entirely to changes occurring in this post-microsomal fraction. These changes may be the effect of accumulation in the post-microsomal fraction of breakdown products from the endoplasmic reticulum, which is known to be sensitive to protein intake.