title: Macromolecular covalent binding of [14C]nitrobenzene in the erythrocyte and spleen of rats and mice.
abstract: Nitrobenzene exposure is known to produce red blood cell damage as well as engorgement and sinusoidal congestion of the spleen in male Fischer-344 (F-344) rats but not in male B6C3F1 mice. These studies were conducted to investigate the species differences in the covalent binding of [14C]nitrobenzene in the erythrocyte and spleen and to assess the contribution of nitrobenzene-induced erythrocytic damage to the splenic effects. Total and covalently bound 14C concentrations in erythrocytes of rats were 6-13 times greater than those of mice following a single oral dose of 75, 150, 200 or 300 mg/kg [14C]nitrobenzene, suggesting that species differences in nitrobenzene-induced red blood cell toxicity may be related to differences in erythrocytic accumulation of nitrobenzene and its metabolites. Covalently bound 14C in erythrocytes of rats peaked 24 h following administration of 200 mg [14C]nitrobenzene/kg; in contrast, bound radiolabel in erythrocytes from mice plateaued at 10 h. Splenic engorgement increased in a time-related manner in treated rats but not in mice. Species specificity was also observed in the accumulation of bound radiolabel in the spleen. Gel filtration and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) of lysed, dialyzed erythrocytes from treated rats revealed that hemoglobin was the primary, if not the exclusive, site of macromolecular covalent binding following nitrobenzene treatment. SDS-PAGE of dialyzed rat spleens revealed that 82% of total bound 14C migrated identically to hemoglobin. These data indicate that covalent binding of [14C]nitrobenzene and its metabolites in the spleen is primarily derived from bound 14C from scavenged erythrocytes. Therefore, the species differences in splenic engorgement and accumulation of [14C]nitrobenzene may be related to differences in susceptibility to nitrobenzene-induced red blood cell damage.
mesh_terms: D000818:Animals; D004305:Dose-Response Relationship, Drug; D004591:Electrophoresis, Polyacrylamide Gel; D004912:Erythrocytes / Q000378:metabolism*; D046911:Macromolecular Substances; D008297:Male; D051379:Mice; D009578:Nitrobenzenes / Q000378:metabolism*; D009929:Organ Size / Q000187:drug effects; D051381:Rats; D011916:Rats, Inbred F344; D013154:Spleen / Q000378:metabolism*; D013997:Time Factors
chemical_list: D046911:Macromolecular Substances; D009578:Nitrobenzenes; C036077:nitrobenzene