Dynamics of O2 consumption in rat pancreatic islets

Abstract

Summary The O₂ consumption of rat pancreatic islets was determined by monitoring pO₂ in the perifusate from groups of 200–300 islets. Basal respiration was maintained for up to 2 h. The insulin secretagogues, glucose and 4-methyl-2-oxopentanoate, provoked an immediate (2 consumption and the ability of glucose and 4-methyl-2-oxopentanoate to increase islet respiration. 2,4-Dinitrophenol increased islet O₂ consumption. The omission of Ca²⁺ and Mg²⁺ from the perifusing media, or the addition of the ionophore A23187, had little effect on respiration. The omission of K⁺ inhibited glucose-induced changes but had a lesser effect in the absence of substrate or in the presence of 4-methyl-2-oxopentanoate. The omission of HCO₃ ^- reduced both basal and secretagogue-induced changes in islet respiration. It is concluded that mitochondrial O₂ consumption linked to oxidative phosphorylation is a major component in the respiratory response, and that some energy consuming process in the islets depends on the availability of HCO₃ ^-. Mitochondrial reactions may generate a signal initiating the secretory process.