H+-induced membrane depolarization in canine cardiac Purkinje fibers.
The H+-induced membrane depolarization in canine cardiac Purkinje cells in false tendons was studied. In some electrically paced Purkinje cells ("sensitive" cells), exposure to a pH 6.0 superfusate produced a large membrane depolarization [44.5 +/- 6.7 (SD) mV], whereas other Purkinje cells ("resistant" cells) developed only a small depolarization (9.8 +/- 5.6 mV) even after 60 min of exposure to the low-pH superfusate. Cs+, Ba2+, tetraethylammonium, 9-aminoacridine, verapamil, or exposure to Ca2+- or K+-deficient or hypertonic solutions were capable of converting resistant cells to sensitive cells. Increasing extracellular K+ concentration [( K+]) or rapid electrical pacing failed to convert resistant cells to sensitive cells. Membrane depolarizations of approximately equal magnitude produced in Purkinje cells by either increasing [K+] to 18.2 mM, decreasing [K+] to 0.5 mM, reducing extracellular pH to 4.1, or ouabain administration were associated with membrane resistances of approximately 45, 377, 386, or 45%, respectively, of the membrane resistances in the control solution. The results suggest that the H+-induced membrane depolarization in sensitive Purkinje cells is caused by a mechanism similar to that responsible for a low [K+]-induced depolarization.
D000585:Aminacrine / Q000494:pharmacology; D000818:Animals; D001464:Barium / Q000494:pharmacology; D002118:Calcium / Q000502:physiology; D002586:Cesium / Q000494:pharmacology; D004285:Dogs; D006329:Heart Conduction System / Q000502:physiology*; D006863:Hydrogen-Ion Concentration; D008564:Membrane Potentials; D011188:Potassium / Q000494:pharmacology; D011690:Purkinje Fibers / Q000502:physiology*; D012462:Saline Solution, Hypertonic; D013757:Tetraethylammonium Compounds / Q000494:pharmacology; D014700:Verapamil / Q000494:pharmacology
D012462:Saline Solution, Hypertonic; D013757:Tetraethylammonium Compounds; D002586:Cesium; D001464:Barium; D000585:Aminacrine; D014700:Verapamil; D011188:Potassium; D002118:Calcium