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A study of the ion selectivity and the kinetic properties of the calcium dependent slow inward current in mammalian cardiac muscle.
Author(s) -
Reuter H,
Scholz H
Publication year - 1977
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1977.sp011656
Subject(s) - conductance , chemistry , current (fluid) , voltage clamp , reversal potential , ion , membrane potential , time constant , biophysics , analytical chemistry (journal) , calcium , electrode , cardiac action potential , electrophysiology , patch clamp , thermodynamics , repolarization , chromatography , biochemistry , medicine , biology , physics , receptor , organic chemistry , engineering , electrical engineering , condensed matter physics
1. A voltage‐clamp method combining a single surcose gap and two intracellular micro‐electrodes was used to measure membrane currents in ventricullar myocardial fibres. 2. The adequacy of the voltage‐clamp method is demonstrated by comparing the total current, It, across the gap with the voltage difference, delta V, between the two intracellular micro‐electrodes, i.e. another independent way of measuring membrane currents. With both current measurements the slow inward current, Is, shows the same voltage‐ and time‐dependences. 3. The sensitivity of the slow inward current to variation in external Ca and Na concentrations was investigated systematically. The reversal potential of the slow inward current was sensitive to variation of both ion species. 4. From the reversal potential measurements relative permeabilities of the conductance channels of the slow inward current were estimated as PCa/PNa approximately 1/0‐01 and PCa/PK approximately 1/0‐01 by means of the constant field equation. 5. The activation and inactivation kinetics of the slow inward current were explored in detail and related to the plateau of the action potential.