This Article Full Text Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Díaz, M.E. Articles by Eisner, D.A. Search for Related Content PubMed PubMed Citation Articles by Díaz, M.E. Articles by Eisner, D.A.

(Circulation Research. 1996;78:857-862.)
© 1996 American Heart Association, Inc.

Articles

Variability of Spontaneous Ca²⁺ Release Between Different Rat Ventricular Myocytes Is Correlated With Na⁺-Ca²⁺ Exchange and [Na⁺]_i

M.E. Díaz, S.J. Cook, J.P. Chamunorwa, A.W. Trafford, M.K. Lancaster, S.C. O'Neill, D.A. Eisner

From the Department of Veterinary Preclinical Sciences, University of Liverpool (UK).

Correspondence to Dr D.A. Eisner, Department of Veterinary Preclinical Sciences, University of Liverpool, Liverpool L69 3BX, UK. E-mail eisner@liverpool.ac.uk.

Abstract We have studied the factors responsible for the variation of the frequency of "waves" caused by spontaneous Ca²⁺ release in rat ventricular myocytes. The experiments were performed in isolated myocytes using the fluorescent indicators Indo-1 (to measure [Ca²⁺]_i) and SBFI (to measure [Na⁺]_i). After electrical stimulation (either with action potentials or voltage-clamp pulses), some cells showed spontaneous Ca²⁺ release. The frequency of this release, where present, was variable. The Ca²⁺ content of the sarcoplasmic reticulum (SR) was measured by applying caffeine (10 mmol/L). The resulting increase of [Ca²⁺]_i activated the electrogenic Na⁺-Ca²⁺ exchange, and the integral of this current was used to estimate the Ca²⁺ content of the SR. The SR Ca²⁺ content was significantly higher in cells that oscillated at high rates (>10·min^-1) than in those that were quiescent. The rate of removal of Ca²⁺ from the cytoplasm by non-SR mechanisms was measured by adding caffeine (10 mmol/L) and measuring the rate constant of decay of the resulting increase of [Ca²⁺]_i. Cells that had a high rate constant of decay of [Ca²⁺]_i had a low frequency of oscillations. Measurements of [Na⁺]_i showed a positive correlation between the frequency of spontaneous SR Ca²⁺ release and [Na⁺]_i. After cessation of stimulation, there was a gradual decrease of [Na⁺]_i, which was correlated with a parallel decrease of the frequency of oscillation rate. We conclude that the variability of frequency of spontaneous SR Ca²⁺ release is due to variations of the rate of Ca²⁺ removal from the cell, which are probably due to Na⁺-Ca²⁺ exchange. The variability of Na⁺-Ca²⁺ exchange rate, in turn, is likely to result from variations of [Na⁺]_i.

Key Words: Ca²⁺ • sarcoplasmic reticulum • Na⁺ • Na⁺-Ca²⁺ exchange

This article has been cited by other articles:

				T. Liu and B. O'Rourke Enhancing Mitochondrial Ca2+ Uptake in Myocytes From Failing Hearts Restores Energy Supply and Demand Matching Circ. Res., August 1, 2008; 103(3): 279 - 288. [Abstract] [Full Text] [PDF]

				G. Smith Matters of the heart: the physiology of cardiac function and failure Exp Physiol, November 1, 2007; 92(6): 973 - 986. [Abstract] [Full Text] [PDF]

				A. A. Werdich, F. Baudenbacher, I. Dzhura, L. H. Jeyakumar, P. J. Kannankeril, S. Fleischer, A. LeGrone, D. Milatovic, M. Aschner, A. W. Strauss, et al. Polymorphic ventricular tachycardia and abnormal Ca2+ handling in very-long-chain acyl-CoA dehydrogenase null mice Am J Physiol Heart Circ Physiol, May 1, 2007; 292(5): H2202 - H2211. [Abstract] [Full Text] [PDF]

				L. Hove-Madsen, A. Llach, A. Bayes-Genis, S. Roura, E. R. Font, A. Aris, and J. Cinca Atrial Fibrillation Is Associated With Increased Spontaneous Calcium Release From the Sarcoplasmic Reticulum in Human Atrial Myocytes Circulation, September 14, 2004; 110(11): 1358 - 1363. [Abstract] [Full Text] [PDF]

				A. Chorvatova, G. Hart, and M. Hussain Na+/Ca2+ exchange current (INa/Ca) and sarcoplasmic reticulum Ca2+ release in catecholamine-induced cardiac hypertrophy Cardiovasc Res, February 1, 2004; 61(2): 278 - 287. [Abstract] [Full Text] [PDF]

				B. Pieske and S. R Houser [Na+]i handling in the failing human heart Cardiovasc Res, March 15, 2003; 57(4): 874 - 886. [Abstract] [Full Text] [PDF]

				S. M Pogwizd, K. R Sipido, F. Verdonck, and D. M Bers Intracellular Na in animal models of hypertrophy and heart failure: contractile function and arrhythmogenesis Cardiovasc Res, March 15, 2003; 57(4): 887 - 896. [Full Text] [PDF]

				Y. Wu, R. J. Colbran, and M. E. Anderson Calmodulin kinase is a molecular switch for cardiac excitation -contraction coupling PNAS, February 27, 2001; 98(5): 2877 - 2881. [Abstract] [Full Text] [PDF]

				K. R. Sipido, P. G. A. Volders, S. H. M. de Groot, F. Verdonck, F. Van de Werf, H. J. J. Wellens, and M. A. Vos Enhanced Ca2+ Release and Na/Ca Exchange Activity in Hypertrophied Canine Ventricular Myocytes : Potential Link Between Contractile Adaptation and Arrhythmogenesis Circulation, October 24, 2000; 102(17): 2137 - 2144. [Abstract] [Full Text] [PDF]

				P. G.A. Volders, M. A. Vos, B. Szabo, K. R. Sipido, S.H.M. de Groot, A. P.M. Gorgels, H. J.J. Wellens, and R. Lazzara Progress in the understanding of cardiac early afterdepolarizations and torsades de pointes: time to revise current concepts Cardiovasc Res, June 1, 2000; 46(3): 376 - 392. [Full Text] [PDF]

				E. Carmeliet Cardiac Ionic Currents and Acute Ischemia: From Channels to Arrhythmias Physiol Rev, July 1, 1999; 79(3): 917 - 1017. [Abstract] [Full Text] [PDF]