Oxidative degradation of haemoglobin by nitrosobenzene in the erythrocyte

Substitutions on the benzene ring of nitrosobenzene did not have the same effect on oxidative haemolysis as substitutions on phenylhydrazine. We previously found that the haemolytic effect of arylhydrazines paralleled their oxidative conversion into ligands of ferrihaemoglobin. In contrast, although most substituted nitrosobenzenes that are ligands of ferrohaemoglobin caused haemolysis and most that are not ligands failed to cause nitrosoarenes appeared to be related more closely to the ease of their reduction to arylhydroxylamines than to their properties as ligands. We propose a mechanism of oxidative degradation whereby the cyclic formation of phenylhydroxylamine from nitrosobenzene within an erythrocyte leads to the accumulation of H2O2, which then reacts with ferrohaemoglobin to initiate the oxidative cleavage of haem. The posulated active intermediate in this reaction is the same as that previously proposed in the oxidative degradation of haemoglobin by phenylhydrzine and in the coupled oxidation of ascorbic acid and haemoglobin.