Open AccessUse of calcium ionophores to determine the effects of intracellular calcium on the action potential of canine cardiac Purkinje fibers.
Author(s) -
Jeremiah M. Gelles
Publication year - 1977
Publication title -
circulation research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.899
H-Index - 336
eISSN - 1524-4571
pISSN - 0009-7330
DOI - 10.1161/01.res.41.1.94
Subject(s) - purkinje fibers , calcium , membrane potential , biophysics , depolarization , cardiac action potential , chemistry , electrophysiology , diastolic depolarization , ionophore , calcium in biology , ventricular action potential , afterdepolarization , potassium , medicine , endocrinology , repolarization , biology , sinoatrial node , heart rate , organic chemistry , blood pressure
The effects of calcium ionophores X-537A, A23187, and PR-47 on the action potential of canine cardiac Purkinje fibers were studied using standard microelectrode techniques. The ionophores hyperpolarize the membrane potential, eliminate the notch on the action potential plateau, decrease action potential duration, decrease plateau amplitude and duration, decrease spontaneous diastolic depolarization and excitability, and decrease the rate effect on action potential duration. These effects were shown to be independent of catecholamines, membrane-bound calcium, and the patency of the slow inward current channel. The effects of the ionophores depended on the presence of calcium in the external solution. A plausible interpretation of the data is that an ionophore-mediated increase in intracellular calcium shifts the voltage dependence of transmembrane potassium currents to more negative levels.
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