ACTIVITY OF CYTOSOLIC AND MITOCHONDRIAL-ENZYMES PARTICIPATING IN NUTRIENT CATABOLISM OF NORMAL AND TUMORAL ISLET CELLS

The aim of the present study is to compare normal and tumoral pancreat ic islet cells in terms of both the activity of selected cytosolic and mitochondrial enzymes participating to nutrient catabolism and the in trinsic properties of FAD-glycerophosphate dehydrogenase. The activity of the glycolytic enzymes hexokinase and lactate dehydrogenase was hi gher in tumoral (RINm5F) than normal islet cells. The opposite was see n for glutamate decarboxylase, glutamate-oxaloacetate transaminase, gl utamate-pyruvate transaminase, glutamate dehydrogenase, 2-ketoglutarat e dehydrogenase and FAD-glycerophosphate dehydrogenase (m-GDH). These findings are consistent with the high rates of glycolysis and protein synthesis seen in tumoral islet cells compared with normal islet cells , which favour mitochondrial oxidative events associated with the cata bolism of D-glucose and amino acids. The intrinsic catalytic propertie s of m-GDH were comparable, albeit not identical, in normal and tumora l islet cells. Since a deficiency of m-GDH in pancreatic islets may re present a contributing factor in the pathogenesis of non-insulin-depen dent diabetes, it is proposed that RINm5F cells may readily yield suff icient islet m-GDH for purification and further gene cloning.