R. Ramirez et al., THE COUPLING OF METABOLIC TO SECRETORY EVENTS IN PANCREATIC-ISLETS - GLUCOSE-INDUCED CHANGES IN MITOCHONDRIAL REDOX STATE, Biochimica et biophysica acta. Bioenergetics, 1273(3), 1996, pp. 263-267
Mitochondrial NAD(+), NADH, NADP(+) and NADPH were measured in dispers
ed pancreatic islet cells incubated in the absence or presence of D-gl
ucose and then exposed for 20 s to 0.5 mg/ml digitonin. The latter tre
atment resulted in the full release of lactate dehydrogenase without a
ny detectable loss of glutamate dehydrogenase. The permeabilized cells
were separated from the incubation medium by centrifugation through a
n oil layer and their content in pyridine nucleotides measured by a ra
dioisotopic procedure coupled to the classical cycling technique. Rela
tive to basal value, D-glucose, in concentrations of 2.8 and 16.7 mM,
caused a concentration-related increase in both the NADH/NAD(+) and NA
DPH/NADP(+) ratio. These findings provide the first direct evidence fo
r the induction of a more reduced mitochondrial redox state in glucose
-stimulated pancreatic islets.