Comparison of the uptake and distribution of chromate in rats and mice

The purpose of this study was to evaluate species differences in tissue accumulation of chromium. Rats and mice were orally exposed to Cr(VI) (potassium chromate) via drinking water (8 mg/d/kg body wt for 4 or 8 wk) or by ip injection (0.3 and 0.8 mg/d/kg, for 4 or 14 d). Chromium concentrations were measured by atomic absorption spectrophotometry, and tissues were compared for exposure route and species differences. After oral exposure, irrespective of treatment duration, liver concentrations of chromium were three to four times higher in mice than rats, whereas kidney concentrations were about 50% lower. However, after ip injection, kidney and blood concentrations in rats were two- and four-fold, higher, respectively. Both rats and mice showed high values of Cr concentration in the bone. After single ip injection of Na₂ ⁵¹CrO₄; Cr concentrations were higher in the blood of rats than mice both after 24 and 72 h. Red blood cell concentrations of Cr were also greater in rats than mice by approximately threefold, whereas white blood cell Cr concentrations were higher in mice than rats. There was also a twofold greater binding of Cr/μmol of hemoglobin in rats compared to mice. These data indicate that species differences exist for Cr metabolism and that they differ with respect to the route of exposure. These results may be owing to species differences in the reduction of Cr and different binding of Cr to hemoglobin.