Effect of hypoxic cell radiosensitizers on glutathione level and related enzyme activities in isolated rat hepatocytes.
A comparative study of the effect of misonidazole and novel radiosensitizers on glutathione (GSH) levels and related enzyme activities in isolated rat hepatocytes was performed. Incubation of hepatocytes with 5 mM radiosensitizers led to a decrease in the intracellular GSH level. The most pronounced decrease in cellular GSH was evoked by 2,4-dinitroimidazole-1-ethanol (DNIE); after incubation for only 15 min, GSH was hardly detected. DNIE-mediated GSH loss was dependent upon its concentration. DNIE reacted with GSH nonenzymatically as well as with diethylmaleate, while misonidazole and 1-methyl-2-methyl-sulfinyl-5-methoxycarbonylimidazole (KIH-3) did not. Addition of partially purified glutathione S-transferase (GST) did not enhance DNIE-mediated GSH loss in a cell-free system. DNIE inhibited glutathione peroxidase (GSH-Px), GST, and glutathione reductase (GSSG-R) activities in hepatocytes, while misonidazole and KIH-3 did not. GSH-Px activity assayed with H2O2 as substrate was the most inhibited. Inhibition of GSH-Px activity assayed with cumene hydroperoxide as substrate and GST was less than that of GSH-Px assayed with H2O2 as substrate. GSSG-R activity was decreased by DNIE, but not significantly. Incubation of purified GSH-Px with DNIE resulted in a little change in the activity when assayed with H2O2 as substrate.
D000818:Animals; D004305:Dose-Response Relationship, Drug; D005978:Glutathione / Q000378:metabolism*; D005979:Glutathione Peroxidase / Q000378:metabolism; D005980:Glutathione Reductase / Q000378:metabolism; D005982:Glutathione Transferase / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000378:metabolism; D000860:Hypoxia / Q000139:chemically induced*; D007093:Imidazoles / Q000494:pharmacology; D008099:Liver / Q000187:drug effects / Q000201:enzymology*; D008297:Male; D008920:Misonidazole / Q000494:pharmacology; D009593:Nitroimidazoles / Q000494:pharmacology; D011838:Radiation-Sensitizing Agents / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D013997:Time Factors
D007093:Imidazoles; D009593:Nitroimidazoles; D011838:Radiation-Sensitizing Agents; C020169:2,4-dinitroimidazole-1-ethanol; C045987:1-methyl-2-methylsulfinyl-5-methoxycarbonylimidazole; D008920:Misonidazole; D006861:Hydrogen Peroxide; D005979:Glutathione Peroxidase; D005980:Glutathione Reductase; D005982:Glutathione Transferase; D005978:Glutathione