Electrophysiological effects of hypertonic sucrose solutions on canine cardiac Purkinje fibers.

Microelectrode techniques were used to study the electrophysiological effects of hypertonic solutions on canine cardiac Purkinje fibers. Tyrode's solution was rendered hyperosmotic by the addition of sucrose to produce 320, 350, 400, and 500 mOsm solutions. Hyperosmotic solutions produced sucrose concentration-dependent hyperpolarization, increased the current required to effect all-or-none depolarization, slowed transmission, and prolonged action potential duration. The action potential prolongation was reversed or prevented by lidocaine (10-5 M). Treatment of potassium-depolarized Purkinje fibers with hypertonic solutions produced hyperpolarization, increased Vmax phase 0, decreased the current required to evoke all-or-none depolarization, increased action potential duration, and increased transmission speed. The potent electrophysiological actions of hypertonic sucrose solutions probably derive from their osmotic effects rather than from selective actions at specific membrane sites or hormone receptors.