ラット摘出膵灌流実験におけるぶどう糖およびアルギニン刺激のインスリン・グルカゴン分泌に対するメチレンブルーの効果

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To examine the role of NADPH in the release of insulin and glucagon, isolated rat pancreata were perfused with methyleneblue, which is known to oxidize NADPH.<BR>Hormonal release was stimulated by changes in arginine or glucose concentrations as follows. After establishing the basal secretion state during perfusion at various glucose levels for 10 min., pancreata were stimulated by the addition of arginine or a change in glucose concentration of the perfusate for 15 min. Conditions for the stimulation were : (A) addition of 10 mM arginine at constant 4 mM glucose concentration; (B) increase in glucose concentration from 2.8 mM to 11.1 mM, or (C) decrease in glucose concentration from 11.1 mM to 2.8 mM. In some experiments, methyleneblue was added throughout the perfusion period at 1 or 3 μg/ml. The effluent from the portal vein was collected over 1 minute intervals : Insulin and glucagon concentrations in the effluent were determined by radioimmunoassay.<BR>Insulin release. Stimulation by the addition of arginine and increased glucose concentration produced a typical biphasic insulin response. In both cases, 1 μg/ml methyleneblue reduced the second phase, and 3 μg/ml methyleneblue inhibited both phases almost completely.<BR>Glucagon release : Stimulation by arginine and inhibition by increasing glucose concentration were not influenced by methyleneblue; however, glucagon release induced by lowering of glucose concentration was suppressed by 3 μg/ml of methyleneblue.<BR>Thus, methyleneblue specifically inhibits glucose- and arginine-induced insulin release while it has no effect on arginine-induced glucagon release. The results are interpreted in support of the fact that NADPH levels regulate insulin release. The observed glucose-stimulated release of insulin could therefore be mediated by increased levels of NADPH resulting from the intracellular metabolism of glucose.
一般社団法人日本内分泌学会の論文

ラット摘出膵灌流実験におけるぶどう糖およびアルギニン刺激のインスリン・グルカゴン分泌に対するメチレンブルーの効果

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