Inhibition of gamma-glutamyl transpeptidase and induction of glutathionuria by gamma-glutamyl amino acids.

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Abstract
Treatment of mice with various .gamma.-glutamyl amino acids leads to marked urinary excretion of glutathione and other .gamma.-glutamyl compounds. There is good correlation between the affinity of .gamma.-glutamyl transpeptidase for various .gamma.-glutamyl amino acids and the extent of glutathionuria. The findings indicate that the administered .gamma.-glutamyl compounds effectively compete with glutathione (exported from kidney cells and present in the glomerular filtrate) for the enzyme. The administration of certain .gamma.-glutamyl amino acids appears to be a specific and nontoxic procedure for in vivo inhibition of .gamma.-glutamyl transpeptidase that may be useful in experimental work on glutathine metabolism and function and also for treatment of certain toxicities and for modulation of the metabolism of endogenous glutathione conjugates.