Effect of protein deprivation of male weanling rats on the kinetics of hepatic microsomal enzyme activity.

TLDR: It is suggested that the diminution of enzyme velocities for the low protein group is related both to a lower DNA content per gram tissue and to a loss of specific enzymic activity per milligram microsomal protein.

Abstract: The effect of protein deficiency in male weanling rats on the activity of the hepatic microsomal enzyme system was studied. Animals were divided into three groups and were fed for 15 days either a semipurified diet con taining 5% casein (group 1), 20% casein pair-fed to the 5% casein group (group 2) or 20% casein fed ad libitum (group 3). The liver weight, as a per centage of body weight, was higher in group 1. For group 1 animals, microsomal protein and DNA, when expressed per gram of liver, were approximately one-half the contents of groups 2 and 3. Maximal velocities for ethylmorphine (EM) and aniline (AN) were lower in group 1, whether these rates are expressed per milli gram microsomal protein, per gram liver or per 100 g body weight. A comparison of these methods of expression suggested that the diminution of enzyme velocities for the low protein group is related both to a lower DNA content per gram tissue and to a loss of specific enzymic activity per milligram microsomal protein. The Kmfor ethylmorphine was lower and that for aniline was higher in group 1 ani mals. Restriction of food intake affected enzyme kinetic parameters similar to protein deficiency but to a significantly lesser degree. Alternative explanations for this effect of protein deficiency are discussed and an involvement of phospho- lipid is suggested. J. Nutr. 102: 53-60, 1972.