Cadmium action on aminopeptidase N activity and L-threonine intestinal transport in rabbit.

Cadmium has been recognized as an environmental contaminant. In oral cadmium intoxication, the immediate target organ is the gastrointestinal tract. The aim of the present work was to study the effect of cadmium on the intestinal absorption of L-threonine and on the aminopeptidase N activity in rabbit jejunum, after in vitro addition and/or oral administration of CdCl2 in drinking water. Results obtained show that cadmium decreases L-threonine absorption in the jejunal tissue. This effect seems to be due to an action mainly on active amino-acid transport at the mucosal border of the intestinal epithelium, because cadmium does not seem to modify the amino-acid diffusion across the intestinal epithelium. Cadmium also inhibits the (Na(+)-K+)-ATPase activity of the enterocyte, which might explain the inhibition of the Na(+)-dependent L-threonine transport. Nevertheless, a direct action of the cadmium ion on the carrier of active transport cannot be rejected. Cadmium modifies the aminopeptidase N activity when administered in drinking water for 4 d.