The Effect of Vitamin a Deficiency upon the Nitrogen Metabolism of the Rat

Abstract

Young and adult rats from the same litters were divided into 3 groups, vitamin A-deficient, pairfed and fullfed on a diet containing 18% casein, and their nitrogen metabolism studied for 30 to 124 days. Another group of young rats was placed on a 22% casein diet and was similarly studied. As the deficiency progressed, growth per gram of protein eaten declined in the deficient young rats to 65% of that of the pairfed groups. The urinary nitrogen increased and the nitrogen balance was decreased to a greater degree in the deficient than in the pairfed young animals. But in the adult group weight changes and nitrogen balances were alike in the pairfed and deficient rats. The urinary nitrogen partitions were essentially alike in the pairfed and deficient groups except in the severely deficient and premortal periods when the allantoin output of the deficient animals was increased above that of the pairfed litter mates. The composition of the carcasses of the fullfed, pairfed and deficient young rats remained constant except for the fat content which was diminished in the latter group with corresponding increase in water. As shown by carcass analysis, the retention of food nitrogen by the pairfed and fullfed young rats was the same in both series, but that of the deficient groups was only 55 and 62% of these values. The deficiency state, as distinct from the accompanying inanition, decreased the utilization of nitrogen in the young animals without affecting the character of the nitrogen metabolism except in the terminal period. The adult deficient and pairfed groups exhibited no differences in nitrogen metabolism. Vitamin A may therefore be considered essential for the growth of tissue protein but not for its maintenance.