[Absorption of D-glucose by the small intestine of the human fetus (using brush border membrane vesicles of the jejunum)].

using brush border membrane vesicles prepared from human mid gestational fetal intestine (jejunum), the intestinal D-glucose transport mechanism was studied using a rapid filtration technique. The uptake of D-glucose into the vesicles was osmotically sensitive. This finding indicated that the uptake of D-glucose into the vesicles represented transport into the vesicles. A Na+ electrochemical gradient (extravesicular greater than intravesicular) stimulated the initial rate of D-glucose uptake, and Na+ dependent uptake of D-glucose into vesicles showed a typical overshoot phenomenon. This overshoot and the initial rate of uptake were markedly increased when the intravesicular space was rendered electrically more negative by membrane diffusion potentials induced by the use of highly permeant anions. A similar stimulation of D-glucose uptake was observed, when membrane potential (inside negative) was imposed by K+ diffusion potentials via valinomycin. These results indicated that a sodium dependent uptake of D-glucose into the brush border membrane vesicles was dependent on the electrical potential difference of the membrane. The initial rate of D-glucose transport exhibited saturation kinetics with respect to the D-glucose concentration; an apparent Km of 3.2mM and Vmax of 8.1n mol/mg protein/20 sec were calculated. In conclusion the mid gestational fetal intestine (jejunum) already has a D-glucose absorption system which is comparable to the adult one.