The effect of erythrocytes and hemoglobin on sister chromatid exchange induction in cultured human lymphocytes exposed to aniline HCI.

Erythrocytes [red blood cells (RBCs)] possess aniline hydroxylase activity. When aniline interacts with ferrohemoglobin in the presence of molecular oxygen, oxidation of nitrogen and ring carbons occurs. Thus, apart from the liver, RBCs may represent an important site of aniline metabolism. Because 2 metabolites of aniline, o-aminophenol and phenylhydroxylamine, can induce sister chromatid exchanges (SCEs), we examined the ability of RBCs and hemoglobin to activate aniline to genotoxic intermediates as evidenced by SCE induction in human lymphocytes. Aniline HCI (0.05-1.0 mM) induced significant concentration-related increases in the SCE frequency only in the whole blood cultures. Similarly, inhibition of cell cycle kinetics by aniline was observed only in the whole blood cultures, as shown by a concentration-dependent decrease in the percentage of third- (and later) division metaphases. Mitotic indices were not affected significantly at any concentration of aniline or hemoglobin. Hemoglobin (500 or 1,000 micrograms/ml) alone induced significant concentration-related increases in SCEs in the mononuclear leukocyte cultures. Therefore, human mononuclear leukocytes do not activate aniline to genotoxic intermediates capable of inducing SCEs during a 48-hr exposure. However, the inclusion of RBCs and granulocytes provides an activation system as demonstrated by a small, but statistically significant increase in the SCE frequency in the whole blood cultures. The weak genotoxicity of hemoglobin may be related to production of oxygen radicals during autoxidation to methemoglobin.(ABSTRACT TRUNCATED AT 250 WORDS)