Some Effects of Restriction of Dietary Protein on the Intracellular Components of Liver

The effect of restriction of dietary protein on the chemical composition of the liver has received considerable attention in recent years.While this organ as a whole has been found to be profoundly influenced by protein depletion of the animal, little information has appeared in the literature concerning the effects of such an experimental procedure on the composition of the various morphological components of the liver cell per se.With the advent of relatively simple centrifugation techniques for the separation of liver cells into nuclear, mitochondrial, microsomatic, and residual cytoplasmic components (1, Z), it is now feasible to investigate the specific intracellular fractions as they are affected by restriction of dietary protein.As an initial effort in this direction, the present study was undertaken to determine the site of changes occurring in the liver cells of protein-depleted rats with respect to the concentrations of nitrogen, total phosphorus, nucleic acids, and riboflavin.These chemical constituents were chosen for experimental consideration since the manner in which their concentrations are influenced in the whole liver has been previously investigated.EXPERIMENTAL Twenty female rats of the Wistar strain, between 15 and 17 weeks of age and weighing between 170 and 234 gm., were placed on a normal diet, adequate in all respects, for a period of 7 days.At the end of this time ten of the animals were placed on a protein-free diet for a period of 21 days.The remaining ten animals served as controls and were continued on the normal diet for 21 days.The normal diet consisted of commercial casein 24 per cent, glucose 63 per cent, corn oil 8 per cent, Salts 4 (3) 4 per cent, and dried brewers' yeast 1 per cent.The protein-free diet was similar in composition except that the casein was replaced by an equal amount of glucose.The following vitamins were incorporated into each 100 gm. of diet in the amounts indi-