Intestinal maturation: In Vivo zinc transport

We investigated with an in vivo single pass perfusion technique net absorption and the lumen to mucosa flux of zinc in the proximal and distal small intestine and in the colon segments of suckling (2-wk-old), weanling (3-wk-old) and adolescent (6-wk-old) rats. The concentration of zinc in the isotonic sodium chloride solution perfused through the intestinal segments was either below (10 µM) or above (25, 50, and 100 µM) serum zinc level. In suckling rats, the relationship between luminal zinc concentration and net absorption and lumen to mucosa flux was curvilinear in the proximal segment only; however, the relationship was linear in the distal small intestine and colon. In weanling rats, the relationship between luminal zinc concentration and net absorption and lumen to mucosa flux was curvilinear in the proximal and distal small intestinal segments and linear in the colon segments. In the adolescent rats, the relationship between luminal zinc concentration, net absorption and lumen to mucosa flux was curvilinear in all intestinal segments studied. The curvilinear relationships noted fits a Michaelis-Menten kinetics. Analysis of the kinetic data indicate a progressive rise in mean Km values with age in the proximal segments of all age groups. Similarly, there was a rise in mean Km values in the distal segments of the weanling and adolescent rats. These findings suggest that intestinal zinc transport is characterized by a maturational pattern which evolves with age.