Cadmium uptake and bioaccumulation in Xenopus laevis embryos at different developmental stages.

The uptake of cadmium in Xenopus laevis embryos was studied by exposing them to solutions containing cadmium concentrations ranging from 0.1 to 2 mg Cd2+/L at seven developmental stages for 72 h. The uptake values were from 0.0027 microgram Cd2+/embryo (two blastomeres stage) to 0.081 microgram Cd2+/embryo, (hindlimb bud distinct stage). During early developmental stages, a limited permeability to cadmium could play a significant role for the survival of embryos. At the last developmental stage evaluated there was a significantly higher uptake of cadmium simultaneously with a very significant increase in the resistance against cadmium toxicity. The cadmium bioaccumulation factor (BF) ranged from 5 to 460. As a general pattern at all developmental stages the BF was higher in embryos exposed to the lower cadmium concentration, and as development advanced the BF increased.