Amino Acid Imbalance and Tryptophanniacin Metabolism

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Abstract
The effect of feeding excess leucine on the urinary excretion of tryptophan-niacin metabolites and nitrogen was studied in young and adult rats. Urinary excretion of quinolinic acid and N′methylnicotinamide was increased in both young and adult rats when L-leucine was added at 1.5% level to a 9% casein diet. Quinolinic acid excretion was more markedly affected in young rats, whereas N′-methylnicotinamide excretion was more affected in adult rats. Isoleucine counteracted the effect of leucine in young rats. Nitrogen excretion increased on leucine feeding in adult rats but not in young rats. Adult rats fed a jowar (Sorghum vulgare) diet tended to excrete relatively more N′-methylnicotinamide and niacin than when fed a wheat diet.