Strategies for the use of bio-indicators in the prediction of environmental damage should include mechanistic research. This study involves the relationship between the chemical structure and hemotoxic markers of aniline and its halogenated analogs. Aniline-induced methemoglobinemia, loss of circulating blood cells, blood stability, glutathione depletion and membrane cytoskeletal changes were assessed following exposure to phenylhydroxylamine (PHA), para-fluoro-, para-bromo-, and para-iodo in

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... le Sprague-Dawley rats. Methemoglobin was determined spectrophotometrically at 635 nm. Erythrocyte depletion was investigated by loss of radioactivity in chromium-labeled red blood cells in vivo. Membrane proteins were analyzed by SDS-PAGE using red blood ghost cells treated with various aniline analogs. Results showed dose-and time-dependent changes in the induction of methemoglobin of up to 78 % with para-bromo PHA and 75 % with para-iodo PHA compared to 3 % to 5 % in control. Treated animals lost up to three times more blood from circulation compared to control within 14 days after treatment. Erythrocytes were more stable in buffer solution than in para-iodo-treated cells. Depletion of reduced glutathione in PHA and para-iodo-PHA treated red cells was also observed. Analysis of red cell skeletal membrane treated with para-iodo-PHA showed that protein band 2.1 became broader and band 2.2 diminished completely in some treatments. Dose-and time-dependent changes suggested the use of hemotoxic endpoints as potential biomarkers for assessing chemical and drug safety.