The hemotoxicity of para-substituted aniline analogs in dog and rat erythrocytes: a species comparison.

INTRODUCTION Hemolytic anemia, the early removal of erythrocytes from the circulation, has been recognized as a side effect of drugs and other environmental chemicals. Formation of methemoglobin (MetHb) following chemical exposure is the first hemotoxic response in the induction of hemolytic anemia. The purpose of this study was to compare the species differences in the chemical induction of MetHb in dog and rat erythrocytes exposed to para-substituted halogenated aniline analogs (phenylhydroxylamine, p-bromo-, p-fluoro-, and p-iodo-phenyhydroxylamine). METHODS Whole blood was collected from a healthy, male Dalmatian dog that weighed 51 lbs and male Sprague-Dawley rats that weighed 100-125 g. Cells were washed (x3) with phosphate-buffered saline supplemented with glucose (pH 7.4). Methemoglobin (MetHb) induction was determined by treating aliquots with pre-specified micromoles of the test agents. Aliquots (75 microL) were removed from each treatment group at specific time points and mixed with cold hemolysis buffer for MetHb determination. Methemoglobin (MetHb) was determined spectrophotometrically at 635 nm. RESULTS Methemoglobin (MetHb) levels in dog erythrocytes treated with the four analogs increased continuously over 180 minutes and showed no signs of declining. Methemoglobin (MetHb) levels in rat erythrocytes, however, immediately increased and continued to rise and fall before gradually approaching control levels. CONCLUSIONS Our data demonstrated the species differences in the MetHb-inducing ability of the analogs tested in both dog and rat erythrocytes. The differences in the patterns associated with MetHb induction in the animal models used may be attributed to variations in the MetHb reductase enzyme in both species.