UPTAKE MECHANISM OF TRIENTINE BY RAT INTESTINAL BRUSH-BORDER MEMBRANE-VESICLES

The uptake characteristics of trientine by rat intestinal brush-border membrane vesicles were studied. The uptake characteristics of trienti ne were similar to those of the physiological polyamines with respect to the excessive accumulation in vesicles, the pH dependency, the temp erature dependency and the ineffectiveness of K+ diffusion potential ( inside negative). The initial uptake of trientine was saturable with a K-m value of 1.13 mM, which was larger than that of spermine and sper midine. Furthermore, the uptake rate of trientine was dose-dependently inhibited by spermine and spermidine. Spermine competitively inhibite d the uptake of trientine with a K-i value of 18.6 mu M, and it was cl ose to the K-m value for spermine (30.4 mu M). These data suggested th at the uptake of trientine was similar to that of spermine and spermid ine in rat small intestinal brush-border membrane vesicles, and these polyamines seem to inhibit the absorption of trientine from the gastro intestinal tract.