Potassium Transfer Kinetics in the Isolated Dog Heart. Influence of Contraction Rate, Ventricular Fibrillation, High Serum Potassium and Acetylcholine

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Abstract
Potassium transfer kinetics were studied in the perfused isolated dog heart with the aid of radioactive tracer (K42) techniques. The effects of heart rate, ventricular fibrillation, high serum potassium and acetylcholine on cell-interstitial fluid potassium exchange were investigated. A positive linear correlation between potassium exchange and heart rate was found. Potassium transfer per beat was less than that found previously in the in vivo dog heart. A relative increase in potassium flux was noted when the heart was arrested by high serum potassium or slowed by acetylcholine. A relative decrease in calculated potassium flux accompanied ventricular fibrillation. The results suggest that potassium exchange between the myocardial cell and interstitial fluid is a function of heart rate, and that extracellular potassium concentration, acetylcholine and possibly the strength of myofibril contraction are other factors influencing exchange. The decreased exchange in ventricular fibrillation may reflect incomplete cell membrane depolarization.