N-hydroxy-N-arylacetamides. III: Mechanism of haemoglobin oxidation by N-hydroxy-4-chloroacetanilide in erythrocytes in vitro.
N-Hydroxy-4-chloroacetanilide(N-hydroxy-4C1AA) was the most active, and N-hydroxy-2-acetylaminofluorene(N-hydroxy-2AAF) the least active compound among six N-hydroxy-N-arylacetamides, in forming ferrihaemoglobin(HbFe3+) in bovine erythrocytes in the presence of 11 mM glucose. N-Hydroxy-4C1AA oxidized 25 equiv. of HbFe2+, both in the presence and absence of glucose or lactate. Therefore, its catalytic properties did not depend on metabolic regeneration by the NADPH- or NADH-dependent erythrocyte reductases. In contrast, N-hydroxy-4-chloroaniline(N-hydroxy-4C1A) oxidized 760 equiv. of HbFe2+ in the presence of glucose, but only 81 equiv. of HbFe2+ in the presence of lactate. These results indicate that the catalytic activity depended on the metabolic regeneration from 4-chloronitrosobenzene(4-C1NOB) by NADPH-dependent erythrocyte reductases. A relationship was established between HbFe3+ concn. and the concn. of N-hydroxy-4C1A and 4-C1NOB(determined together), 4-chloroacetanilide(4-C1AA) and 4-chloroaniline(4-C1A), indicating co-oxidation of N-hydroxy-4C1AA and oxyhaemoglobin in erythrocytes and partial reduction of the newly formed 4-C1NOB to 4-C1A. In rat blood in vitro incubated with N-hydroxy-4C1AA, 4-C1NOB concn. increased with increasing HbFe3+ concn., indicating that 4-C1NOB was formed by co-oxidation of oxyhaemoglobin and N-hydroxy-4C1AA, and not by enzymic N-deacetylation.
D000083:Acetanilides / Q000494:pharmacology*; D000818:Animals; D002417:Cattle; D004912:Erythrocytes / Q000378:metabolism*; D005260:Female; D006454:Hemoglobins / Q000378:metabolism*; D006881:Hydroxyacetylaminofluorene / Q000494:pharmacology; D006898:Hydroxylamines / Q000494:pharmacology; D007700:Kinetics; D008297:Male; D008706:Methemoglobin / Q000378:metabolism; D009603:Nitroso Compounds / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains
D000083:Acetanilides; D006454:Hemoglobins; D006898:Hydroxylamines; D009603:Nitroso Compounds; C052916:N-hydroxy-4-chloroacetanilide; D006881:Hydroxyacetylaminofluorene; C018485:4-chlorophenylhydroxylamine; D008706:Methemoglobin; C018484:4-chloronitrosobenzene