Low Activities of Glutathione-related Enzymes As Factors in the Genesis of Urinary Bladder Cancer

A comparative study of reduced glutathione (GSH) concentrations and activities of GSH related-enzymes in urinary bladder transitional epithelium (UBTE), urinary bladder nontransitional tissue (UBNT), and liver of the rabbit, was carried out to investigate the reasons for the susceptibility of UBTE towards peroxidase-mediated chemical carcinogenesis. Cooxidative activation of chemical carcinogens by prostaglandin H synthase occurs at high levels in UBTE and minimally in UBNT. Other peroxidases are also likely to activate carcinogenic xenobiotics in the urinary bladder. GSH concentrations in UBTE and UBNT were low compared to that in the liver. gamma-Glutamyl transpeptidase activities were much lower in UBTE and in UBNT than those in the liver. Activities of selenium-dependent and selenium-independent glutathione peroxidases were very low in UBTE and UBNT. Cytosolic glutathione S-transferase activity towards 1,2-epoxy-(4-nitrophenoxy)propane was very low in UBTE. Microsomal glutathione S-transferase activity towards 1-chloro-2,4-dinitrobenzene was much lower in UBTE than in the liver. We propose that the low GSH concentration and diminished activities of glutathione peroxidases, gamma-glutamyl transpeptidase, and certain isozymes of glutathione S-transferase could be responsible for the vulnerability of UBTE towards chemical carcinogenesis.