DEXTROSE-INDUCED, ADENOSINE-INDUCED AND MAGNESIUM-INDUCED PROTECTIVE ACTIONS DURING ANOXIA AND REPERFUSION IN CANINE PURKINJE TISSUE

1. The effects of dextrose, magnesium (Mg) and adenosine on membrane p otential and force of contraction were studied in driven and overdrive n canine cardiac Purkinje tissue. 2. Dextrose (50 mmol/L) and adenosin e (4-6 mmol/L) both showed protective action (the latter to a lesser e xtent) against simulated anoxia and reperfusion- induced arrhythmias, increased force of contraction transiently on reperfusion, and the for mer sustained the increase in force to a lower level as long as it was in the superfusing solution; 3. Dextrose (50 mmol/L) and Mg (5 mmol/L ) restored overdrive- induced hyperpolarization during simulated anoxi a. Adenosine was largely ineffective. 4. It was concluded that dextros e and adenosine (to a lesser extent) protect against arrhythmias by re plenishing the critical intracellular pool of ATP which controls membr ane transport of electrolytes such as K and Ca. Restoration of Na-K AT Pase activity alone (as in the case of high Mg concentrations) is not sufficient to prevent arrhythmias.