A role for the glutathione peroxidase/reductase enzyme system in the protection from paracetamol toxicity in isolated mouse hepatocytes.
The role of the glutathione peroxidase/reductase (GSH-Px/GSSG-Rd) enzyme system in protection from paracetamol toxicity was investigated in isolated mouse hepatocytes in primary culture. The effect of inhibitors of these enzymes on the toxicity of paracetamol and on t-butylhydroperoxide (t-BOOH), used as a positive control, was determined. 1,3-Bis(chloroethyl)-1-nitrosourea (BCNU) was used to inhibit GSSG-Rd, and goldthioglucose (GTG) used to inhibit GSH-Px. Both these inhibitors increased cell membrane damage in response to oxidative stress initiated by t-BOOH. However, they also increased the susceptibility of hepatocytes to paracetamol toxicity, indicating that a component of paracetamol's toxic effect involves formation of species that are detoxified by the GSH-Px/GSSG-Rd enzymes. To further examine the role of these enzymes, age-related differences in their activity were exploited. Hepatocytes from two-week-old mice were less susceptible to both t-BOOH and paracetamol toxicity than were those from adult mice. This corresponds to higher activity of cytosolic GSH-Px/GSSG-Rd in this age group. However, after inhibition of GSSG-Rd with BCNU, hepatocytes from these postnatal mice were more susceptible to paracetamol toxicity. This suggests that the higher activity of GSH-Px/GSSG-Rd in hepatocytes from two-week-old mice is responsible for their reduced susceptibility to paracetamol toxicity. The data indicate that the GSH-Px/GSSG-Rd enzymes contribute to protection from paracetamol toxicity and suggest that formation of peroxides contributes to this drug's hepatotoxic effects.
Adamson
G M
GM
Department of Pharmacology, University of Western Australia, Nedlands.
Harman
A W
AW
D000082:Acetaminophen / Q000633:toxicity*; D000367:Age Factors; D000818:Animals; D016227:Benzoquinones; D002330:Carmustine / Q000494:pharmacology; D005978:Glutathione / Q000032:analysis; D005979:Glutathione Peroxidase / Q000502:physiology*; D005980:Glutathione Reductase / Q000502:physiology*; D007097:Imines / Q000494:pharmacology; D066298:In Vitro Techniques; D008099:Liver / Q000187:drug effects*; D051379:Mice; D010084:Oxidation-Reduction; D010545:Peroxides / Q000494:pharmacology; D020122:tert-Butylhydroperoxide
D016227:Benzoquinones; D007097:Imines; D010545:Peroxides; D000082:Acetaminophen; D020122:tert-Butylhydroperoxide; D005979:Glutathione Peroxidase; D005980:Glutathione Reductase; C028473:N-acetyl-4-benzoquinoneimine; D005978:Glutathione; D002330:Carmustine