Anoxic atrial and ventricular muscle electrical activity, cell potassium, and metabolism: A comparative study

Abstract

The action potential duration of anoxic guinea pig atrial muscle declined at a slower rate than that of ventricular muscle when incubated in 5 m m-glucose medium. Since previous work has demonstrated a relationship between action potential duration, ATP content and lactate production in anoxic ventricular muscle, ATP and lactate production were compared in the two tissues. At dissection and following a 1-h aerobic equilibration period, ventricular muscle had a higher ATP content than atrial muscle. During anoxic incubation the ATP content declined in both tissues, but after 1 h it was significantly higher in atrial than in ventricular muscle. Atrial muscle produced more lactate than ventricular muscle during anoxic incubation in 0, 5, or 50 m m-glucose medium. The difference in lactate production during incubation with 5 and 50 m m-glucose was less in atrial than in ventricular muscle. Similarly, the difference in action potential duration and intracellular potassium concentration during incubation with 5 and 50 m m-glucose was less in atrial than in ventricular muscle. It was concluded that atrial muscle has higher endogenous glycogen stores and during anoxia maintains function to a greater degree than ventricular muscle by a more efficient uptake or utilization of exogenous glucose.