Effects of intracellular calcium on sodium current density in cultured neonatal rat cardiac myocytes

Nipavan Chiamvimonvat, M. E. Kargacin, R. B. Clark, H. J. Duff

Research output: Contribution to journalArticle

42 Scopus citations

Abstract

Na+ channel mRNA levels in the heart can be modulated by changes in intracellular Ca2+ ([Ca2+](i)). We have investigated whether this regulation of Na+ channel biosynthesis by cytosolic Ca2+ translates into functional Na+ channels that can be detected electrophysiologically. Whole-cell Na+ currents (I(Na)) were recorded using patch-clamp techniques from single ventricular myocytes isolated from neonatal rats and maintained in tissue culture for 24 h. Na+ current density, measured at a membrane potential of -10 mV, was significantly decreased in the cells which were exposed for 24 h to culture medium containing 10 mM of both external Ca2+ and K+ in order to raise [Ca2+](i) compared with control cells which were maintained in culture medium containing 2 and 5 mM of Ca2+ and K+, respectively. In contrast, Na+ current density (at -10 mV) was significantly increased in cells exposed for 24 h to 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetra-acetic acid tetraacetoxymethyl ester (BAPTA AM; a cell membrane-permeable Ca2+ chelator) which lowered the average [Ca2+](i) compared with control. Changes in current density were not associated with changes in the voltage dependence of activation and inactivation of I(Na). There were no changes in single-channel conductances. It is concluded that Na+ current density in neonatal rat cardiac myocytes is modulated by [Ca2+](i) The findings suggest that the differences in current density are attributable to a change in Na+ channel numbers rather than to changes in single-channel conductance or gating. These changes are consistent with the previously documented modulation of Na+ channel biosynthesis by cytosolic Ca2+

Original languageEnglish (US)
Pages (from-to)307-318
Number of pages12
JournalJournal of Physiology
Volume483
Issue number2
StatePublished - 1995
Externally publishedYes

ASJC Scopus subject areas

  • Physiology

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