Pyruvate Metabolism in Thiamine-deficient Calves

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Abstract
Three to four hours after feeding, 2 thiamine-deficient and 2 control calves were injected intravenously with pyruvate-2-14C. The specific activity of respired CO2 reached maximal values 20 minutes after the injection of pyruvate-2-14C in the control animals and after 35 and 60 minutes in the two deficient calves. The rate of CO2 excretion was the same in control and deficient calves. The proportion of CO2 arising from pyruvate was 40 and 30%, respectively, for one control and deficient calf. The amount of 14C incorporated into liver glutamate, aspartate, alanine, serine, and glycine per millicurie of 14C injected/kg body weight was higher in deficient than in control calves. The intramolecular distribution of 14C in liver glutamate indicated that relatively more of the carbon from pyruvate was incorporated into the tricar boxylic acid cycle via CO2 fixation in the deficient calves compared with their controls. These data indicate that thiamine deficiency affects the route of metabolism of pyruvate in the calf, apparently diminishing the fraction metabolized through acetyl-CoA.