Cadmium in caribou (Rangifer tarandus) kidneys: speciation, effects of preparation and toxicokinetics

Caribou kidney is a major source of cadmium (Cd) in the traditional diets of many aboriginal communities in the Arctic. In order to characterize the risk of Cd exposure, we studied the speciation of Cd in caribou kidneys and how it can be affected by food preparation. Cd in caribou kidneys was bound to metallothionein (MT) (40%), high molecular weight proteins (50-500 kDa) (30%) and existed as free ions (10%). There was no change in Cd concentrations after the samples were baked at 350°C for 30min but the MT level was significantly decreased. Food preparation also denatured the high molecular weight proteins, resulting in a significant increase of free Cd. The toxicokinetics of Cd in caribou kidney was studied using a rodent model. Four groups (n = 6) of adult Sprague-Dawley rats were fed with rat chow with the addition of one of the following: 10% veal kidney with 0 µg/g Cd, 10% veal kidney spiked with CdCl to make up to 66 µg/g Cd; 2 10% caribou kidney containing 20 µg/g Cd and 10% caribou kidney containing 66 µg/g Cd. After 14 days, Cd accumulation increased with dose but less than 1% of the dosed Cd accumulated in the liver and kidney of rats. The percentage of Cd accumulated in the liver was higher in the group fed with caribou kidney than that dosed with spiked veal kidney. Our results suggest that caribou kidney is a major source of Cd exposure among the Arctic populations but moderate consumption may be considered unavoidable.