Protein metabolism in growing rats. I. Liver arginase activity and body composition in relation to age and dietary protein level

Abstract

A study of food intake body composition and liver arginase activity has been made in groups of albino rats fed on diets containing 4 % and 20 % casein for periods of 15, 30, 60 and on days from weaning. The study also includes body composition and liver arginase activity of rats fed the stock diet of the colony (9 % vegetable protein) and of a weaning group (time o control).

Gain in body weight, food intake and body composition were significantly different in protein-deficient rats. However, there was good correlation between the food intake and body composition of the various groups and their body weight. Caloric intake, total nitrogen and percentage of water and protein in the eviscerated carcass were linear functions of body weight, independent of growth rate and dietary protein level. PER and CUP values were greater during the first month after weaning and less in the following two months. Chan­ges in body constituents (water and proteins) were also greater during the first month.

Livor arginase activity was significant­ly greater in rats fed 20 % casein and stock diets. The former showed evident increased activity levels in relation to age, and there is evidence which suggests a relation between those changes and the protein metabolism in the growing rat, characterized by rapidily increasing catabolism with age.