Differences in glucose handling by pancreatic A- and B-cells.
Glucose exerts opposite effects upon glucagon and insulin release from the endocrine pancreas. Glucose uptake and oxidation were therefore compared in purified A- and B-cells. In purified B-cells, the intracellular concentration of glucose or 3-O-methyl-D-glucose equilibrates within 2 min with the extracellular levels, and, like in intact islets, the rate of glucose oxidation displays a sigmoidal dose-response curve for glucose. In contrast, even after 5 min of incubation, the apparent distribution space of D-glucose or 3-O-methyl-D-glucose in A-cells remains much lower than the intracellular volume. In A-cells, both the rate of 3-O-methyl-D-glucose uptake and glucose oxidation proceed proportional to the hexose concentration up to 10 mM and reach saturation at higher concentrations. Addition of insulin failed to affect 3-O-methyl-D-glucose or D-glucose uptake and glucose oxidation by purified A-cells. Glucose releases 30-fold more insulin from islets than from single B-cells, but this marked difference is not associated with differences in glucose handling. The rate of glucose oxidation is virtually identical in single and reaggregated B-cells and is not altered after addition of glucagon or somatostatin. It is concluded that the dependency of glucose-induced insulin release upon the functional coordination between islet cells is not mediated through changes in glucose metabolism.
D019325:3-O-Methylglucose; D000818:Animals; D005934:Glucagon / Q000494:pharmacology; D005947:Glucose / Q000378:metabolism*; D007328:Insulin / Q000378:metabolism; D007515:Islets of Langerhans / Q000166:cytology* / Q000378:metabolism; D007700:Kinetics; D008297:Male; D008757:Methylglucosides / Q000378:metabolism; D010084:Oxidation-Reduction; D051381:Rats; D011919:Rats, Inbred Strains; D013004:Somatostatin / Q000494:pharmacology
D007328:Insulin; D008757:Methylglucosides; D019325:3-O-Methylglucose; D013004:Somatostatin; D005934:Glucagon; D005947:Glucose