Cadmium accumulation in liver and kidney of mice exposed to the same weekly cadmium dose continuously or once a week

Cd levels in blood, liver and kidney of female mice were measured after exposure to Cd as CdCl2 in the food, either continuously (CE group) throughout the week (300 microg Cd/kg feed) or for 24 hr/wk (2100 microg Cd/kg) for 5 wk (occasionally exposed, OE group). In a control group that received feed with Cd levels below the detection limit (< 7 microg/kg), Cd levels in blood, liver and kidneys were below the detection limit after the 5 wk of exposure. The weekly dose of Cd administered to the exposed CE and OE groups was similar (approx. 400 microg Cd/kg mice/wk). The OE group had a higher Cd level in blood and a higher fractional accumulation (% of dose) of Cd in the liver and kidneys compared with the CE group. This indicates that the fractional Cd absorption in the gastrointestinal tract is higher when high Cd doses are ingested occasionally than when low doses are ingested continuously, even if weekly doses are the same. It is hypothesized that this difference in absorption could be due to Cd-induced unspecific damage to the intestinal mucosa, changes in tight-junction permeability caused by Cd, or to a saturation of the Cd-binding capacity of the intestinal mucosa in mice exposed to high Cd levels occasionally.