Amino acid metabolism in lactic acidosis

Abstract Individual plasma amino acid levels have been determined in six patients with severe lactic acidosis. A consistently distorted pattern was observed whether the disorder was due to shock or was of the idiopathic type. A sixfold elevation in mean alanine concentration was observed, and a significant correlation of alanine with pyruvate concentrations was demonstrated. Since alanine is normally released from muscle and stoichiometrically extracted by liver, normal formation of alanine from pyruvate is suggested by the findings. However, uptake and metabolism of alanine by isolated, perfused rat liver was significantly inhibited by perfusate concentrations of lactate and pyruvate equivalent to those observed in the patients. Thus the high levels of alanine in lactic acidosis are viewed as consistent with normal or increased peripheral release combined with impaired hepatic disposal. The levels of fifteen of the nineteen amino acids measured were elevated. Of the remaining four, three were intermediates of the urea cycle.