AJP - Cell Physiology, Vol 236, Issue 3 103-C110, Copyright © 1979 by American Physiological Society

ARTICLES

The generation of electric currents in cardiac fibers by Na/Ca exchange

L. J. Mullins

The presence of a detectable Ca current during the excitation of a cardiac fiber implies that the Ca lost during the resting interval of the duty cycle must also be detectable. Ca outward movement appears to be effected by Na/Ca exchange when more Na enters than Ca leaves per cycle, thus making the mechanism electrogenic. Since Na/Ca exchange can move Ca either inward or outward depending on the direction of the electrochemical gradient for Na, a potential exists where there is no electric current generated by the Na/Ca exchange mechanism, i.e., a reversal potential ER. Cardiac fibers appear to have a reversal potential that is about midway between their resting membrane potential and their plateau. Carrier currents both inward and outward are therefore generated during cardiac action potentials. The implications of the conditions stated above are explored.

This article has been cited by other articles:

				R. K. Dash and D. A. Beard Analysis of cardiac mitochondrial Na+-Ca2+ exchanger kinetics with a biophysical model of mitochondrial Ca2+ handing suggests a 3: 1 stoichiometry J. Physiol., July 1, 2008; 586(13): 3267 - 3285. [Abstract] [Full Text] [PDF]

				R. Dipolo and L. Beauge Sodium/Calcium Exchanger: Influence of Metabolic Regulation on Ion Carrier Interactions Physiol Rev, January 1, 2006; 86(1): 155 - 203. [Abstract] [Full Text] [PDF]

				J. A. Wasserstrom and G. L. Aistrup Digitalis: new actions for an old drug Am J Physiol Heart Circ Physiol, November 1, 2005; 289(5): H1781 - H1793. [Abstract] [Full Text] [PDF]

				J. G. J. Hoenderop, B. Nilius, and R. J. M. Bindels Calcium Absorption Across Epithelia Physiol Rev, January 1, 2005; 85(1): 373 - 422. [Abstract] [Full Text] [PDF]

				V. Lakireddy, P. Baweja, A. Syed, G. Bub, M. Boutjdir, and N. El-Sherif Contrasting effects of ischemia on the kinetics of membrane voltage and intracellular calcium transient underlie electrical alternans Am J Physiol Heart Circ Physiol, January 1, 2005; 288(1): H400 - H407. [Abstract] [Full Text] [PDF]

				A. G. KLEBER and Y. RUDY Basic Mechanisms of Cardiac Impulse Propagation and Associated Arrhythmias Physiol Rev, April 1, 2004; 84(2): 431 - 488. [Abstract] [Full Text] [PDF]

				Y.-W. Qian, R. J. Sung, S.-F. Lin, R. Province, and W. T. Clusin Spatial heterogeneity of action potential alternans during global ischemia in the rabbit heart Am J Physiol Heart Circ Physiol, December 1, 2003; 285(6): H2722 - H2733. [Abstract] [Full Text] [PDF]

				P. J. Cooper, M.-L. Ward, P. J. Hanley, G. R. Denyer, and D. S. Loiselle Metabolic consequences of a species difference in Gibbs free energy of Na+/Ca2+ exchange: rat versus guinea pig Am J Physiol Regulatory Integrative Comp Physiol, April 1, 2001; 280(4): R1221 - R1229. [Abstract] [Full Text] [PDF]

				K. M. Ito, M. Sato, K. Ushijima, M. Nakai, and K. Ito Alterations of endothelium and smooth muscle function in monocrotaline-induced pulmonary hypertensive arteries Am J Physiol Heart Circ Physiol, October 1, 2000; 279(4): H1786 - H1795. [Abstract] [Full Text] [PDF]

				M. P. Blaustein and W. J. Lederer Sodium/Calcium Exchange: Its Physiological Implications Physiol Rev, July 1, 1999; 79(3): 763 - 854. [Abstract] [Full Text] [PDF]

				M. Flesch, R. H.G. Schwinger, F. Schiffer, K. Frank, M. Sudkamp, F. Kuhn-Regnier, G. Arnold, and M. Bohm Evidence for Functional Relevance of an Enhanced Expression of the Na+-Ca2+ Exchanger in Failing Human Myocardium Circulation, September 1, 1996; 94(5): 992 - 1002. [Abstract] [Full Text]