Tissue distribution of chromium in male Fischer 344 rats and female B6C3F1 mice exposed to sodium dichromate dihydrate in drinking water for 2 years

Abstract

Hexavalent Chromium (Cr VI) is recognized as a human carcinogen when exposure occurs via inhalation. Recently, a 2-year NTP bioassay of sodium dichromate dihydrate (SDD) in drinking water demonstrated clear evidence of carcinogenicity in rats and mice. As part of the 2-year study, chromium (Cr) levels were measured in excreta and tissues from female mice and male rats. SDD was administered in drinking water at concentrations of 0, 14.3, 57.3, 172, and 516 ppm. On days 4, 11, 180, and 369, up to 10 animals per exposure group were removed from treatment and placed in individual metabolism cages for collection of urine and feces (from 0-24 and 24-48 hours); undosed water and feed were provided ad libitum. Liver, kidney, forestomach, glandular stomach, blood and plasma were collected on days 6, 13, 182, and 371. Total Cr in each sample was quantitated by inductively coupled plasma-mass spectrometry. Most of the Cr eliminated was in feces in rats and mice, suggesting that absorption was low. The highest Cr concentrations were found in the kidney, liver and glandular stomach of rats and mice. The concentrations in mouse tissues were generally higher than rat tissues, with liver, forestomach and glandular stomach showing the greatest difference. In both rats and mice, Cr concentrations in erythrocytes and plasma reflected patterns observed in the tissues, but at much lower concentrations. The data from this study will aid in the interpretation of the bioassay results.