The importance of the hydrophobic effect of exogenous substances and of modifications of membrane order on D-glucose uptake are still poorly defined. Our results show that the concentrative Na+ -coupled D-glucose uptake of rat enterocyte brush border membrane vesicles is inhibited by N-phenylcarbamate derivatives. Unlike other series of lipophilic compounds inhibiting D-glucose transport, these N-phenylcarbamates increase the membrane order. However, since the concentrations required for membrane order increase are much greater than those active on D-glucose uptake, the effects on lipid order cannot be resposible for the inhibition of D-glucose uptake. Measurements of D-glucose uptake under conditions of Na+ equilibrium show that these carbamates do not act directly on the carrier but indirectly by favouring the dissipation of the Na+ gradient.
