Effect of leucine-lsoleucine antagonism on plasma amino acid pattern of rats

The rate of stomach-emptying, the nitrogen content of the intestinal contents, and the blood plasma amino acid pattern of rats were determined at various time intervals up to 24 hr. after they had consumed a single low-protein meal containing enough leucine to cause a leucine-isoleucine and valine antagonism. Control groups were fed either the basal diet without additional leucine or the high-leucine diet with extra isoleucine and valine to alleviate the antagonism. No significant differences were found between the rates of stomach-emptying, or between the amounts of nitrogen in the intestinal contents, of the groups fed the high leucine diets with or without extra isoleucine and valine. The concentrations of isoleucine and valine in blood plasma from the group receiving excess leucine alone were lower every hour up to 12 hr. than the respective concentrations in blood plasma from groups fed the basal diet without leucine or the high-leucine diet with added isoleucine and valine. The plasma concentration of threonine, the amino acid most limiting for the growth of rats fed these diets, was nearly the same throughout for the experimental and both control groups. The plasma glutamic acid concentration was elevated when the diet contained an excess of leucine.