Interrelationships Between α and β Anomers of Glucose Affecting both Insulin and Glucagon Secretion in the Perfused Rat Pancreas. II.

Temporal and quantitative relationships between the α and β anomers of glucose on insulin and glucagon secretion were studied in two surgical preparations of the in vitro perfused rat pancreas. α-Glucose was a more effective stimulator of insulin release. β-Glucose, however, though less effective, was a positive modulator when admixed with α-glucose. Dose-response studies showed that α-glucose probably had a smaller apparent Km for insulin secretion, while the Vmax for the two anomers was the same—the effects of the two anomers being indistinguishable at high glucose concentrations (300 mg⁄dl). α-Anomeric stereospecificity was demonstrable equally on both phases of insulin release and was maintained throughout 60-min perfusions. Spontaneous or arginine-stimulated glucagon release was also preferentially inhibited by α-glucose. Since others have shown that glucose uptake and phosphorylation in islets are not α-stereospecific, the data suggest that the initial signal for the first and second phases of insul...