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Amino acid imbalance and tryptophan-niacin metabolism. 1. Effect of excess leucine on the urinary excretion of tryptophan-niacin metabolites in rats



Amino acid imbalance and tryptophan-niacin metabolism. 1. Effect of excess leucine on the urinary excretion of tryptophan-niacin metabolites in rats



J. Nutrition. 86: 100-106



For previous work, on man, see Abst. 1013, Vol. 34. 1. Seven groups each of 6 weanling rats were fed to appetite for 4 weeks on a purified diet with 9% protein from casein, alone or with 1.5% L-leucine, 0.1% DL-tryptophan or 1 mg nicotinic acid per 100 g, or certain combinations of them. At the end urine was collected for 3 days. Excretion of quinolinic acid in 24-h urine was 21/2 times as great when leucine was added; it was significantly increased also by nicotinic acid, and slightly but not significantly by tryptophan. Excretion of N1-methyl-nicotinamide was increased by each substance singly and leucine increased the effect of the other 2. Addition of 0.2% DL-isoleucine counteracted the effect of leucine in respect of both metabolites. No substance significantly affected total N excretion or excretion of total or free nicotinic acid. In another experiment with 6 mature female rats of 130 to 160 g given the basal diet alone for 10 days before and 10 days after a 10-day period during which they had the leucine supplement, leucine led to reduced food intake and increased excretion of N, quinolinic acid, total and free nicotinic acid and N1-methylnicotinamide. The effect on N1-methylnicotinamide was greater and that on quinolinic acid less than in young rats. When leucine was stopped excretion of N increased and of the other substances decreased, but not to the original levels. In a crossover experiment with 6 rats, excretion of N1-methyinicotinamide and total nicotinic acid was slightly but not significantly greater with a diet based on jowar (Sorghum vulgare), which contains more leucine and less tryptophan, than with a diet based on wheat and having about the same nicotinic acid content.

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Accession: 014338577

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PMID: 14294958


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