p-nitrosophenol reduction by liver cytosol from ADH-positive and -negative deermice (Peromyscus maniculatus).
Liver cytosolic fractions are known to catalyze the reduction of certain C-nitroso compounds to their corresponding hydroxylamines and amines. Alcohol dehydrogenase (ADH), NAD(P)H:quinone oxidoreductase, and xanthine and aldehyde oxidases have been implicated as C-nitroso reductases. To probe the role of these cytosolic enzymes in the reduction of C-nitroso compounds we have studied the effects of classical inhibitors of these enzymes on the ability of liver cytosolic fractions from ADH+ and ADH- deermice to reduce p-nitrosophenol to p-aminophenol. Pyrazole, a potent inhibitor of ADH, inhibited NADH-p-nitrosophenol reduction by ADH+ cytosol by > 85%. Thus, ADH contributes substantially to NADH-C-nitroso reduction by cytosol from ADH+ deermice. The NAD(P)H:quinone oxidoreductase inhibitor, dicumarol, inhibited NADH-dependent p-aminophenol formation by about 25%; however, dicumarol potently inhibited the NADPH-dependent formation (90-95%). As expected, cytosol from ADH- deermice did not catalyze pyrazole-sensitive (ADH-dependent) C-nitroso reduction with NADH as the cofactor. Both NADPH- and NADH-p-nitrosophenol reduction by ADH- cytosol were inhibited > 90% by dicumarol. The xanthine oxidase/aldehyde oxidase inhibitor, allopurinol, was without effect on NAD(P)H cytosolic p-nitrosophenol reduction from ADH- and ADH+ deermice under either aerobic or anaerobic conditions. Our findings suggest that in the ADH+ animal, ADH contributes significantly to NADH-dependent C-nitroso reduction by cytosol relative to NAD(P)H:quinone oxidoreductase. NADPH-dependent p-nitrosophenol reduction by liver cytosol of ADH+ animals is mostly dicumarol-sensitive, which implicates NAD(P)H:quinone oxidoreductase as the major NADPH-dependent activity. In ADH- deermice, both NADH- and NADPH-dependent p-nitrosophenol reduction are essentially dicumarol-sensitive (NAD(P)H:quinone oxidoreductase-dependent). Because the toxic expression of C-nitroso compounds is mediated by hydroxylamine intermediates, the present data indicate the importance of considering the role of ADH in the toxic sequelae of nitro and nitroso arenes.
Dudley
B F
BF
Department of Biochemistry, Louisiana State University, Baton Rouge 70803.
Winston
G W
GW
D000426:Alcohol Dehydrogenase / Q000037:antagonists & inhibitors / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D042931:Aldehyde Oxidase; D000445:Aldehyde Oxidoreductases / Q000378:metabolism; D000627:Aminophenols / Q000378:metabolism; D000818:Animals; D000830:Animals, Laboratory; D003600:Cytosol / Q000201:enzymology / Q000378:metabolism*; D001728:Dicumarol / Q000494:pharmacology; D008099:Liver / Q000201:enzymology / Q000378:metabolism*; D009154:Mutation; D009243:NAD / Q000378:metabolism; D016660:NAD(P)H Dehydrogenase (Quinone) / Q000037:antagonists & inhibitors / Q000378:metabolism*; D009249:NADP / Q000378:metabolism; D009603:Nitroso Compounds / Q000378:metabolism*; D010542:Peromyscus; D011720:Pyrazoles / Q000494:pharmacology; D014969:Xanthine Oxidase / Q000378:metabolism
D000627:Aminophenols; D009603:Nitroso Compounds; D011720:Pyrazoles; D009243:NAD; C031280:pyrazole; D009249:NADP; C028992:4-nitrosophenol; D001728:Dicumarol; D000426:Alcohol Dehydrogenase; D014969:Xanthine Oxidase; D000445:Aldehyde Oxidoreductases; D042931:Aldehyde Oxidase; D016660:NAD(P)H Dehydrogenase (Quinone); C026729:4-aminophenol