Absorption mechanism of polaprezinc (zinc L-carnosine complex) by an everted sac method

Abstract

1. The absorption mechanism of polaprezinc (zinc-carnosine chelate compound) was studied in rat by an everted gut sac method. The rates of transport and accumulation of 14C-L-carnosine were proportional to the mucosal concentration of L-carnosine, whereas the rates of transport and accumulation of 65ZnCl2 had become saturated. The Michaelis-Menten constant (Km) = 4.41 mM and maximal rate (Vmax) = 71.83 nmol/min/g for zinc transport and, similarly, Km = 6.21 mM and Vmax = 92.51 mumol/30 min/g for accumulation. 2. The addition of ouabain, 2,4-dinitrophenol (2,4-DNP) and low temperatures reduced the rate of zinc uptake, indicating that zinc transport was considered to be a carrier-mediated process based on Na+,K(+)-ATPase-dependent mechanisms. 3. The concentration of zinc in the gut of the non-fasted rat was greater than that of the fasted rat, suggesting different rates of transport and accumulation. It is suggested that zinc intestinal uptake in rat is regulated by zinc content in the gut. 4. A pharmacokinetic model for transport and accumulation of zinc saturation from the lumen side to the gut was designed, and the calculated values obtained by simultaneous multiline fitting of transport and accumulation of zinc data were in good agreement with the observed values.

Residence Time of Polaprezinc (Zinc L-Carnosine Complex) in the Rat Stomach and Adhesiveness to Ulcerous Sites

“…Each component of polaprezinc, L-carnosine or zinc, is absorbed after dissociation of polaprezinc in the gastrointestinal tract as a function time (27), and then the absorption rate of polaprezinc is slower than those of L-carnosine or zinc sulfate, because time for dissociation is required in the gastrointestinal tract. It is also well known that the zinc absorption is regulated by homeostatic mechanisms (28)(29)(30), and thus, the absorption ratio of 65Zn -polaprezinc is small (about 11 % of the dose at 50 mg/kg) (15). Therefore, no clear differences in plasma concentration profiles of 65Zn-polaprezinc and 65ZnSO4 were observed.…”