Absorption of inorganic, trivalent and hexavalent chromium following oral and intrajejunal doses in rats

The intestinal absorption of trivalent and hexavalent chromium (Cr) given o rally (experiment I) or infused in the intestine (experiment II) was invest igated in rats. The nonabsorbable form of chromium ((Cr2O3)-Cr-51) and wate r-soluble and more absorbable (Na2CrO4)-Cr-51 (the hexavalent form of Cr) w ere compared. Total retention of chromium given orally ranged around 15 per cent of the dose, regardless of the chromium compounds applied. The absorpt ion rate of chromic oxide, which is considered a nonabsorbable compound, wa s 14.4 as a percentage of chromium intake. This result indicates that some loss of chromium has to be taken into account in metabolic trials made by t he indicator method. In isolated rat intestine, from the injected Cr 2.5% o f chromic oxide and 43.2% of sodium chromate were absorbed during an hour ( experiment II). The absorbed chromium was transferred to the liver where th e liver tissue retained 10.9% of chromic oxide and 51.1% of sodium chromate . Radioactivity of v. cava caudalis following intestinal injection of Na2Cr O4 was thirtyfold greater than after Cr2O3 dosing. This phenomenon can be e xplained by the lower blood clearance of chromate. Different absorption rat e of chromate depending on the route of administration could be due to the fact that the hexavalent form given orally was reduced to Cr3+ in the acidi c environment of the stomach. When Na2CrO4 was infused directly in the inte stine of rats, such reduction could not occur. This means that the acidic g astric juice might play a role in inhibiting the intestinal absorption of N a2CrO4 when this compound is given orally.