Biomonitoring of aniline and nitrobenzene. Hemoglobin binding in rats and analysis of adducts.

Covalent binding to hemoglobin was studied to further substantiate the proposal that it may be used for biomonitoring N-substituted aryl compounds. (14C)-Labeled acetanilide and nitrobenzene were orally administered to female Wistar rats and binding indices [Binding(mmol/mol Hb)/Dose(mmol/kg)] determined; these were 12 +/- 1 and 73 +/- 10, respectively. After mild acidic or alkaline hydrolysis, 90% of the bound material was released and identified as aniline by radio thin layer chromatography. This supports the hypothesis that nitroso aryl derivatives, common intermediates in the metabolism of N-substituted aryl compounds, react with SH-groups of hemoglobin to yield sulfinic acid amides. Aniline was furthermore identified and quantified by capillary gas chromatography, using hemoglobin from animals treated with unlabeled aniline and nitrobenzene. Binding indices in this case were 30 +/- 3 and 85 +/- 19, respectively. With this method human blood samples may also be analysed. Although nitrobenzene is known to produce less methemoglobin than aniline, hemoglobin binding is higher. This indicates that hemoglobin binding may be a better index of body burden than methemoglobin levels in biomonitoring N-substituted aryl compounds.