Influence of Glucose on the Transmembrane Action Potential of Guinea‐Pig Papillary Muscle: Metabolic Inhibitors, Ouabain, and Calcium Chloride, and their Interaction with Glucose, Sympathomimetic Amines, and Aminophylline

In a previous report, we have proposed that anaerobic glycolysis alone can maintain an action potential of normal duration in guinea-pig papillary muscle. This proposal followed from the observation that 50 mM glucose, several sympathomimetic amines, and aminophylline all caused the duration of the action potential of muscles, which had been reduced by incubation in a medium containing 5 mM glucose, to return toward control values. This occurred in the presence or absence of oxygen. It was further proposed that the ATP resulting from anaerobic glycolysis was in some way preferentially utilized in the membrane by a process controlling repolarization and therefore the duration of the action potential. The present experiments were undertaken to determine what metabolic pathways were necessary for the glucose effect mentioned above, by the use of the metabolic inhibitors sodium cyanide, iodoacetic acid, and 2,4-dinitrophenol. Secondly, the effects of ouabain and calcium, which are known to modulate the utilization of ATP, on the glucose effect were studied. It was concluded that an intact glycolytic pathway is necessary for the effect of glucose on the electrical activity of papillary muscle and that the effect can be increased or decreased by low or high doses of ouabain, respectively. The actions of ouabain are thought to be due to a stimulation and depression of a membrane ATP-ase.