title: Covalent binding of the phenacetin metabolite p-nitrosophenetole to protein.
abstract: Addition of p-[3H]nitrosophenetole to protein incubations resulted in quantitative binding of radiolabel to protein. Preincubation of protein with N-methylmaleimide to derivatize sulfhydryl groups followed by addition of p-[3H]nitrosophenetole resulted in a 90% decrease in covalent binding. Treatment of the p-[3H]nitrosophenetole protein-bound residue, after extensive solvent washing, with HCl decreased binding by 72% and the corresponding amine, p-phenetidine was detected in the aqueous phase. Inasmuch as incubation of the bound residue with reduced glutathione did not alter protein binding appreciably the involvement of a sulfinanilide S-oxide is suggested. Incubation of p-[3H]phenetidine with microsomal incubation mixtures resulted in NADPH-dependent covalent binding to protein. Treatment of the p-[3H]phenetidine protein-bound residue after extensive solvent washing with HCl decreased binding by 64%. Administration of either p-[3H]phenetidine (500 mg/kg i.p.) or [14C]phenacetin (500 mg/kg i.p.) to mice resulted in covalent binding of radiolabel to protein of liver, lung, kidney, small intestine and blood. Incubation of solvent-washed protein with acid resulted in an approximately 35% decrease in protein binding in lung and blood of both treatment groups.
mesh_terms: D000818:Animals; D005033:Ethylmaleimide / Q000494:pharmacology; D005978:Glutathione / Q000494:pharmacology; D006735:Horseradish Peroxidase / Q000378:metabolism; D006851:Hydrochloric Acid / Q000494:pharmacology; D008297:Male; D051379:Mice; D008862:Microsomes, Liver / Q000378:metabolism; D008956:Models, Chemical; D010615:Phenacetin / Q000031:analogs & derivatives* / Q000378:metabolism*; D010628:Phenetidine / Q000378:metabolism; D011506:Proteins / Q000378:metabolism*; D051381:Rats; D014018:Tissue Distribution
chemical_list: D011506:Proteins; D010628:Phenetidine; C037221:4-nitrosophenetole; D006735:Horseradish Peroxidase; D010615:Phenacetin; D005978:Glutathione; D005033:Ethylmaleimide; D006851:Hydrochloric Acid