Effect of zinc on aminopeptidase N activity and L-threonine transport in rabbit jejunum.

Zinc is a nutritionally essential trace element required for many biological functions to be successfully carried out. The aim of the present work was to study the influence of zinc 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 ZnCl2 in drinking water. Results obtained show that zinc decreases L-threonine absorption in the jejunal tissue. This effect would appear to be owing to an action mainly located in active amino acid transport, because zinc does not seem to modify the amino acid diffusion across the intestinal epithelium, of the mucosal border of the intestinal epithelium. Zinc has also been shown to inhibit the (Na(+)-K+)-ATPase activity of the enterocyte, which might explain the inhibition of the L-threonine Na(+)-dependent transport. Nevertheless, a direct action of the zinc on carriers of active transport cannot be rejected. However, zinc did not significantly modify the aminopeptidase N activity in rabbit jejunum.