PMID: 1206966Dec 1, 1975Paper

Transmembrane inward currents during excitation of the heart (author's transl)

Klinische Wochenschrift
M Kohlhardt

Abstract

During excitation of the myocardial cell 2 transmembrane inward currents occur. The initial fast Na current is responsible for the upstroke of the normal action potential. The slow inward current is triggered at a threshold potential of about -40 mV and causes the plateau phase of action potential. Under physiological conditions Ca ions are the main charge carriers of the slow inward current. Both inward currents are mediated by 2 membrane channels which are independent from each other. The normal excitability of the myocardial cell depends upon the availability of the fast Na channel but the transmembrane Ca supply will be determined by the Ca conductance of the slow channel. After inactivation of the fast Na channel the excitability of the myocardial cell does not disappear completely. In this situation the slow inward current can mediate action potentials (so called Ca action potentials). The slow inward current can be considered as the predominant mediator of the excitation process in the pacemaker cells of the sinoatrial node and the av node. Specific inhibitors of the slow membrane channel (verapamil, D 600, Ni, Co, and Mn ions) block the transmembrane Ca current leading to excitation contraction uncoupling. The excitatio...Continue Reading

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Citations

Jan 1, 1984·Acta Medica Scandinavica. Supplementum·K E Andersson, E D Högestätt
Nov 1, 1977·British Heart Journal·T Pop, D Fleischmann
Jan 1, 1981·Acta Medica Scandinavica. Supplementum·K E Andersson
Jan 8, 2021·The Journal of General Physiology·Jose MilletAriel L Escobar

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