Effects of blood perfusion on electrophysiological properties of isolated canine Purkinje fibers.

Microelectrode techniques were used to study isolated canine Purkinje fibers perfused alternately with Tyrode's solution and extracorporeally circulated arterial blood from heparinized donor dogs. Action potential amplitude and resting membrane potential were similar in both perfusates and varied with the potassium concentration of the perfusate. Action potential duration also varied with the potassium concentration of the perfusate, being shorter when potassium concentration was higher. Conduction in free-running Purkinje fibers usually was more rapid in blood than in Tyrode's solution; this difference often was not related to changes in potassium concentration, maximal slope of phase 0, and action potential amplitude. Automaticity was comparable in both perfusates. Because conduction time in isolated tissues differs during perfusion with blood and Tyrode's solution, it would seem that experiments on conduction performed during blood perfusion might reflect in vivo events more closely than results obtained using Tyrode's solution.