Cytotoxic effects of N-hydroxyparacetamol in suspsensions of isolated rat hepatocytes.
The cytotoxicity of N-hydroxyparacetamol (N-OH-pHAA), a postulated proximate metabolite of the hepatotoxic and nephrotoxic analgesic paracetamol, was studied in suspensions of hepatocytes isolated by collagen-perfusion of livers of male rats. Incubation of cells with 0.25-2.0 mM N-OH-pHAA led after 3-5 hours to increased cell permeability measured by increased trypan blue uptake, increased NADH penetration or leakage of prelabelled 51Cr. N-OH-pHAA rapidly depleted cellular glutathione, 16% of initial levels were seen after 30 min. incubation. 3H-N-OH-pHAA bound covalently to cellular proteins in a time- and concentration-dependent manner, considerably higher binding rates were seen with boiled cells compared to intact cells. Pretreatment of animals with the cytochrome P-450 inducer phenobarbital did not affect N-OH-pHAA cytotoxicity or covalent binding, whereas the cytochrome P-450 inhibitor metyrapone inhibited both cytotoxicity and binding. Lipid peroxidation in hepatocytes could be seen as a limited range of N-OH-pHAA concentrations. In contrast, lipid peroxidation was an early event in cells exposed to carbon tetrachloride. A minimal exposure time of 30 min. of the hepatocytes to N-OH-pHAA was sufficient to elicit cellular damage occurring after 3-5 hours.
D000082:Acetaminophen / Q000031:analogs & derivatives* / Q000378:metabolism* / Q000633:toxicity; D000818:Animals; D002462:Cell Membrane / Q000187:drug effects; D005978:Glutathione / Q000032:analysis; D066298:In Vitro Techniques; D008054:Lipid Peroxides / Q000378:metabolism; D008099:Liver / Q000187:drug effects*; D008297:Male; D011485:Protein Binding; D051381:Rats; D011919:Rats, Inbred Strains
D008054:Lipid Peroxides; D000082:Acetaminophen; C017372:N-hydroxyacetaminophen; D005978:Glutathione