Effects of Carbohydrates on the Oxygen Consumption of Isolated Pancreatic Islets of Mice

Abstract

In studies of the carbohydrate metabolism of mammalian pancreatic [beta] cells, Cartesian divers were used for analyses of the oxygen consumption of isolated surviving islets of Langerhans from obese-hyperglycemic mice. When single islets (dry weight 1-10 [mu]g) were incubated in Krebs-Ringer phosphate buffer at 37 C, the islet cells respired at a constant rate for several hours. A rapid and pronounced elevation of the respiratory rate was observed, when the incubation medium was supplemented with D-glucose in a concentration of 3 mg/ ml. The oxygen uptake increased with glucose concentration in the range 0.5-3 mg/ml. A smaller degree of stimulation of the respiratory rate was obtained with D-mannose and D-fructose. D-Galactose and 2-deoxy-D-glucose had no obvious effects on the endogenous respiration of the islet cells, whereas a slightly inhibitory effect was noted with D-mannoheptulose. In addition, the latter carbohydrate almost completely blocked the effect of glucose on the islet respiration and strongly inhibited the oxygen uptake of islets preincubated with glucose. No corresponding effects were recorded with 2-deoxy-D-glucose. The results are assumed to represent the islet [beta] cells, since in obese-hyperglycemic mice this cell type composes more than 90% of the islet tissue. The present data indicate that glucose is metabolized by mammalian [beta] cells, and support the view that factors intimately related to the glucose breakdown within these cells are concerned with the control of insulin release.