Impairment of cysteine synthesis from methionine in rats exposed to surgical stress.

The activity of liver cystathionase (EC 4.4.1.1) was decreased after 3 d of stress induced by surgery. The rate of L-cysteine synthesis from L-methionine was significantly higher in isolated hepatocytes from controls than in hepatocytes from rats suffering from surgical stress. The half-life of L-[2(n)-3H]methionine was significantly higher in rats submitted to surgical stress than in controls. Plasma L-methionine:L-cystine ratio was higher in stressed rats than in controls. L-cystine uptake was significantly increased in the surgically-stressed rats when compared with the controls. All these facts are consistent with the hypothesis that the observed inhibition of cystathionase is physiologically important and that L-cysteine might be considered as an essential amino acid in cases of surgical stress.