The effect of verapamil on potassium fluxes in canine cardiac Purkinje fibres.

Electrophysiological studies of verapamil on isolated cardiac tissue show its effects to occur during Phase 2 and Phase 4 of the cardiac action potential and to be a result of blocking the slow inward Ca2+ current. It is important to know if verapamil effects the transmembrane movement of ions other than Ca2+. By studying uptake and efflux of 42K by canine cardiac Purkinje fibres in the presence and absence of verapamil (1.1 x 10-6 M-4.4 X 10-6 M), it was found that the drug inhibits both 42K uptake (15%) and efflux (30%).