Diabetes mellitus and the sodium electrochemical gradient across the brush border membrane of rat intestinal enterocytes

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Abstract
The effects of chronic diabetes mellitus of 4–5 weeks duration on the potential difference across the brush border membrane of rat small intestine (Vm) and on Na+-dependent uptake of d-glucose by jejunal brush border vesicles have been studied. Diabetes increased Vm in the jejunum from a mean value of −47.2 mV in control tissue to −57.4 mV in diabetic tissue (Pm. Measurements of Vm during ion-substitution experiments revealed that the conductance of Na+ of the jejunal brush border was reduced by diabetes, whilst K+ and Cl− permeabilities were unaltered. Uptake studies using brush border vesicles and an Na+-electrochemical gradient showed that diabetes caused a 56% increase in the initial rate of uptake of d-glucose but was without effect on the peak to equilibrium ratio. Taken together, data from these two studies suggest that the lower Na+ permeability of the brush border in diabetes enhances the electrical and chemical driving force for active Na+-dependent uptake of glucose by reducing glucose-independent movement of Na+ across this membrane. Finally, the possible humoral factors involvedin this response to diabetes are discussed. Journal of Endocrinology (1989) 123, 453–459

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