Sugar transport by brush border membrane vesicles isolated from human small intestine

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Abstract
Uptake ofd- andl-glucose, and fructose by purified brush border membrane vesicles isolated from human small intestine was studied using a rapid filtration technique. The uptake ofd-glucose by the vesicles was osmotically sensitive and represented transport into an intravesicular space and not binding to the membranes. Transport of both,d- andl-glucose was inhibited by phlorizin. Uptake ofd-fructose into the brush border vesicles was not stimulated by sodium. In the presence of a sodium gradientd-glucose was taken up 5 times faster thanl-glucose. The amount ofd-glucose transported into the vesicles in the presence of a sodium gradient was transiently higher than the amount ofd-glucose taken up at equilibrium (overshoot).d-Glucose transport was stimulated only by a sodium gradient; other monovalent cations had no effect. In the presence of a sodium gradientd-glucose transport was increased by the lipophilic anion thiocyanate and decreased by the nearly impermeable anion sulfate as compared with uptake ofd-glucose in the presence of a sodium chloride gradient. This indicates an influence of the electrical membrane potential on the sodium coupled non-electrolyte transport.

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