Kinetics of transepithelial movement of heavy metals in rat jejunum.

The kinetics of the transepithelial movement of heavy metals were studied in the perfused rat jejunum in situ. The peak appearance time (TET) of Zn, Ni, and Cd in portal venous blood was determined after their transient (10 s) introduction into the intestinal lumen. Observed TET values for these metals were positively correlated with their affinities for metallothionein and agreed with those predicted on the basis of a linear three-compartment model that does not allow for paracellular pathways. Further evidence was provided to support the hypothesis that Cd absorption consists first of Cd binding to negative membrane charges followed by a temperature-dependent internalization step.