Dietary Proteins Correlated with Ribonuclease, Ribonucleic Acid, and Tissue Proteins

Abstract

The nitrogen growth indexes for egg casein, cottonseed flour and wheat gluter were determined for weanling rats. The ratio between RNA and DNA in the liver was highest in rats fed egg, lowest in those fed cottonseed flour or wheat gluten and in between in those fed casein. The ribonuclease activity in the liver was not reduced by low nitrogen intakes but tended to increase with decreased dietary nitrogen and to be higher in rats fed wheat gluten. Serum ribonuclease activity relative to serum protein was highest in animals fed wheat gluten, lowest in animals fed egg, and in between in animals fed casein or cottonseed flour. Total protein with respect to DNA increased in the liver as nitrogen intake was raised and the greatest increases were observed in rats fed egg and casein proteins. A similar increase was found in the muscle where the ratios were higher in animals fed egg or casein than in those fed wheat gluten or cottonseed flour. Protein relative to DNA also increased in the kidney with nitrogen intake but no difference was observed between animals fed the various types of protein. The protein/DNA ratio in the brain was independent of nitrogen intake or the nutritive value of the dietary protein. The lipids migrating electrophoretically with the plasma globulins were, in general, higher in animals fed cottonseed flour or wheat gluten than in animals fed egg or casein.