Diabetes mellitus and the sodium electrochemical gradient across the brush border membrane of rat intestinal enterocytes.
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 (P less than 0.001) but was without effect on ileal Vm. 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 involved in this response to diabetes are discussed.
Debnam
E S
ES
Department of Physiology, Royal Free Hospital School of Medicine, London.
Ebrahim
H Y
HY
D000818:Animals; D001692:Biological Transport; D002712:Chlorides / Q000378:metabolism; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism*; D005947:Glucose / Q000493:pharmacokinetics; D007413:Intestinal Mucosa / Q000378:metabolism / Q000648:ultrastructure*; D007421:Intestine, Small / Q000378:metabolism / Q000648:ultrastructure*; D008297:Male; D008871:Microvilli / Q000378:metabolism; D011188:Potassium / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D012964:Sodium / Q000378:metabolism*
D002712:Chlorides; D012964:Sodium; D005947:Glucose; D011188:Potassium