Lactate production, glucose utilization, glucose oxidation, and insulin release were studied in islets from rat and ob/ob mice. Lactate was determined with a highly sensitive method, based on esterification, subsequent separation, and quantitation with high-performance liquid chromatography. There was a significant lactate production in the absence of glucose, which increased with glucose concentrations up to 3 mmol/l, reaching its half-maximal rate in the presence of 0.2–1.0 mmol/l glucose in both species. Glucose utilization displayed a wider glucose concentration dependence, with a KQ 5 value between 3 and 10 mmol/l glucose. The rates of glucose utilization and lactate production were similar at 3 mmol/l glucose in rat islets and at about 6 mmol/l glucose in ob/ob mice islets. Saturation of lactate production at low glucose concentrations is probably contributing to the observed preferential stimulation of oxidative metabolism at higher concentrations. D-Mannoheptulose caused a marked inhibition of glucose utilization and glucose oxidation at 20 mmol/l glucose in islets from rat or ob/ob mice, as would be expected from a competitive inhibition of glucokinase. By contrast, D-mannoheptulose reduced only marginally the islet metabolism at 3 mmol/l glucose, which is consistent with an effective mannoheptulose-induced inhibition of the glucokinase-dependent, minor part of glucose phosphorylation at this low glucose concentration.
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Islet Studies| August 01 1998
Lactate Production in Pancreatic Islets
Address correspondence and reprint requests to Jorge Tamarit-Rodriguez, Universidad Complutense, Facultad de Medicina, Departamento de Bioquhnica, Madrid-28040 Spain. E-mail: firstname.lastname@example.org
Jorge Tamarit-Rodriguez, Lars-Åke Idahl, Elena Giné, Oscar Alcazar, Janove Sehlin; Lactate Production in Pancreatic Islets. Diabetes 1 August 1998; 47 (8): 1219–1223. https://doi.org/10.2337/diab.47.8.1219
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