Na+ transport in cardiac myocytes; implications for excitation-contraction coupling

Donald M Bers, Sanda Despa

Research output: Contribution to journalArticle

21 Scopus citations

Abstract

Intracellular Na+ concentration ([Na+]i) is very important in modulating the contractile and electrical activity of the heart. Upon electrical excitation of the myocardium, voltage-dependent Na + channels open, triggering the upstroke of the action potential (AP). During the AP, Ca2+ enters the myocytes via L-type Ca 2+ channels. This triggers Ca2+ release from the sarcoplasmic reticulum (SR) and thus activates contraction. Relaxation occurs when cytosolic Ca2+ declines, mainly due to re-uptake into the SR via SR Ca2+-ATPase and extrusion from the cell via the Na +/Ca2+ exchanger (NCX). NCX extrudes one Ca2+ ion in exchange for three Na+ ions and its activity is critically regulated by [Na+]i. Thus, via NCX, [Na+] i is centrally involved in the regulation of intracellular [Ca 2+] and contractility. Na+ brought in by Na+ channels, NCX and other Na+ entry pathways is extruded by the Na +/K+ pump (NKA) to keep [Na+]i low. NKA is regulated by phospholemman, a small sarcolemmal protein that associates with NKA. Unphosphorylated phospholemman inhibits NKA by decreasing the pump affinity for internal Na+ and this inhibition is relieved upon phosphorylation. Here we discuss the main characteristics of the Na+ transport pathways in cardiac myocytes and their physiological and pathophysiological relevance.

Original languageEnglish (US)
Pages (from-to)215-221
Number of pages7
JournalIUBMB Life
Volume61
Issue number3
DOIs
StatePublished - 2009

Keywords

  • Na channels
  • Na/Ca exchanger
  • Na/K ATPase
  • Phospholemman

ASJC Scopus subject areas

  • Biochemistry
  • Cell Biology
  • Clinical Biochemistry
  • Molecular Biology
  • Genetics

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