<p>This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.</p> <p>To determine the effect of D-glucose on the β-cell
Na<sup>+</sup>/K<sup>+</sup> pump, <sup>86</sup>Rb<sup>+</sup> influx was studied in isolated,
-cell-rich islets of Umeå-<italic>ob/ob</italic> mice in the absence
or presence of lmM ouabain. D-glucose (20 mM)
stimulated the ouabain-sensitive portion of <sup>86</sup>Rb<sup>+</sup>
influx by 65%, whereas the ouabain-resistant
portion was inhibited by 48%. The Na<sup>+</sup>/K<sup>+</sup> ATPase
activity in homogenates of islets of Umeå-<italic>ob/ob</italic>
mice or normal mice was determined to search for
direct effects of D-glucose. Thus, ouabain-sensitive
ATP hydrolysis in islet homogenates was measured
in the presence of different D-glucose concentrations.
No effect of D-glucose (3–20 mM)
was observed in either <italic>ob/ob</italic> or normal islets at
the optimal Na<sup>+</sup>/K<sup>+</sup> ratio for the enzyme (135 mM
Na<sup>+</sup> and 20 mM K<sup>+</sup>). Neither D-glucose (3–20 mM)
nor L-glucose or 3-<italic>O</italic>-methyl-D-glucose (20 mM)
affected the enzyme activity at a high Na<sup>+</sup>/K<sup>+</sup>
ratio (175 mM Na<sup>+</sup> and 0.7mM K<sup>+</sup>). Diphenylhydantoin
(150 μM) decreased the enzyme activity at
optimal Na<sup>+</sup>/K<sup>+</sup> ratio, whereas 50 μM of the drug
had no effect. The results suggest that D-glucose
induces a net stimulation the Na<sup>+</sup>/K<sup>+</sup> pump of β-cells in intact islets and that D-glucose does
not exert any direct effect on the Na<sup>+</sup>/K<sup>+</sup> ATPase activity.</p>
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Int J Exp Diabetes Res. 2000; 1(2):155-164