Distribution of cadmium after oral administration of cadmium-thionein to mice

Abstract

Distribution of Cd was compared after oral administration of either Cd ions or Cd-thionein (Cd-TH). Mice received 0.5 mg Cd/kg, po as CdCl 2 in saline, CdCl 2 in control rat liver homogenate, Cd-TH in saline, Cd-TH in liver homogenate, or liver homogenate from Cd-treated rats. In all cases, 85–90% of the Cd dose was present in feces within 24 hr. However, in groups receiving CdCl 2, more Cd was found in feces on Days 2 and 3 in comparison to those receiving Cd-TH. All treatments resulted in lower levels of Cd in liver than in kidney. In addition, tissue levels indicate that less Cd was absorbed when rats received Cd-TH in saline than CdCl 2 in saline. Cd-TH added to liver homogenate or liver homogenate containing Cd-TH increased the absorption of Cd resulting in renal Cd levels similar to those in mice receiving CdCl 2 in saline. The kidney/liver Cd concentration ratio (9) was the same for Cd-TH in all three media. Although Cd-TH gave much higher kidney/liver Cd ratios than CdCl 2 (9 vs 2), renal Cd concentrations were the same or lower than after CdCl 2 treatments. Results indicate that the high kidney/liver Cd ratio after Cd-TH treatment versus CdCl 2 is due to lower concentrations of Cd in liver rather than marked increases in renal Cd levels. Heating of Cd-TH did not result in lower amounts of Cd in kidney. While the chemical form of Cd administered affects the absorption and distribution of Cd, the amount of Cd reaching the kidney after Cd-TH administration is similar to that after CdCl 2 administration.