HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) All Versions of this Article: 545/2/453    most recent 2002.025866v1 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 Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Hinata, M. Articles by Kimura, J. Search for Related Content PubMed PubMed Citation Articles by Hinata, M. Articles by Kimura, J.

Stoichiometry of Na⁺-Ca²⁺ exchange is 3:1 in guinea-pig ventricular myocytes

Masamitsu Hinata, Hisao Yamamura *, Libing Li, Yasuhide Watanabe †, Tomokazu Watano, Yuji Imaizumi * and Junko Kimura

In single guinea-pig ventricular myocytes, we examined the stoichiometry of Na⁺-Ca²⁺ exchange (NCX) by measuring the reversal potential (E_NCX) of NCX current (I_NCX) and intracellular Ca²⁺ concentration ([Ca²⁺]_i) with the whole-cell voltage-clamp technique and confocal microscopy, respectively. With given ionic concentrations in the external and pipette solutions, the predicted E_NCX were -73 and -11 mV at 3:1 and 4:1 stoichiometries, respectively. E_NCX measured were -69 ± 2 mV (n = 11), -47 ± 1 mV (n = 14) and -15 ± 1 mV (n = 15) at holding potentials (HP) of -73, -42 and -11 mV, respectively. Thus, E_NCX almost coincided with HP, indicating that [Ca²⁺]_i and/or [Na⁺]_i changed due to I_NCX flow. Shifts of E_NCX (E_NCX) were measured by changing [Ca²⁺]_o or [Na⁺]_o. The measured values of E_NCX were almost always smaller than those expected theoretically at a stoichiometry of either 3:1 or 4:1. Using indo-1 fluorescence, [Ca²⁺]_i measured under the whole-cell voltage-clamp supported a 3:1 but not 4:1 stoichiometry. To prevent Ca²⁺ accumulation, we inhibited I_NCX with Ni²⁺ and re-examined E_NCX during washing out Ni²⁺. With HP at predicted E_NCX at a 3:1 stoichiometry, E_NCX developed was close to predicted E_NCX and did not change with time. However, with HP at predicted E_NCX for a 4:1 stoichiometry, E_NCX developed initially near a predicted E_NCX for a 3:1 stoichiometry and shifted toward E_NCX for a 4:1 stoichiometry with time. We conclude that the stoichiometry of cardiac NCX is 3:1.

This article has been cited by other articles:

				H. E. D. J. ter Keurs and P. A. Boyden Calcium and Arrhythmogenesis Physiol Rev, April 1, 2007; 87(2): 457 - 506. [Abstract] [Full Text] [PDF]

				S. Yamanishi, K. Katsumura, T. Kobayashi, and D. G. Puro Extracellular lactate as a dynamic vasoactive signal in the rat retinal microvasculature Am J Physiol Heart Circ Physiol, March 1, 2006; 290(3): H925 - H934. [Abstract] [Full Text] [PDF]

				B. A. Ahlers, X.-Q. Zhang, J. R. Moorman, L. I. Rothblum, L. L. Carl, J. Song, J. Wang, L. M. Geddis, A. L. Tucker, J. P. Mounsey, et al. Identification of an Endogenous Inhibitor of the Cardiac Na+/Ca2+ Exchanger, Phospholemman J. Biol. Chem., May 20, 2005; 280(20): 19875 - 19882. [Abstract] [Full Text] [PDF]

				D. W. Hilgemann New insights into the molecular and cellular workings of the cardiac Na+/Ca2+ exchanger Am J Physiol Cell Physiol, November 1, 2004; 287(5): C1167 - C1172. [Abstract] [Full Text] [PDF]

				B. Bolck, G. Munch, P. Mackenstein, M. Hellmich, I. Hirsch, H. Reuter, N. Hattebuhr, H.-J. Weig, M. Ungerer, K. Brixius, et al. Na+/Ca2+ exchanger overexpression impairs frequency- and ouabain-dependent cell shortening in adult rat cardiomyocytes Am J Physiol Heart Circ Physiol, October 1, 2004; 287(4): H1435 - H1445. [Abstract] [Full Text] [PDF]

				C. R. Weber, K. S. Ginsburg, and D. M. Bers Cardiac Submembrane [Na+] Transients Sensed by Na+-Ca2+ Exchange Current Circ. Res., May 16, 2003; 92(9): 950 - 952. [Abstract] [Full Text] [PDF]