“In vitro, various treatments with 1 mM GSH, 1 mM glutamic acid (Glu), 1 mM glycine (Gly), 0.4 mM Cys and/or 0.2 mM cystine (CysCys) inhibited dramatically the sharp decline in the intracellular ratio of GSH/GSSG caused by 0.1 microM TPA.”
“… Cys on both the decrease … ODC activity by TPA were greatly reduced by the inhibitors of gamma-glutamyl transpeptidase and gamma-glutamylcysteine synthetase, it is suggested that some of … promotion could result from their interference with the metabolism of the tripeptide GSH, a natural antioxidant which inhibits chemical carcinogenesis.”