title: Na⁺ transport in the normal and failing heart - remember the balance.
abstract: In the heart, intracellular Na(+) concentration ([Na(+)]i) is a key modulator of Ca(2+) cycling, contractility and cardiac myocyte metabolism. Several Na(+) transporters are electrogenic, thus they both contribute to shaping the cardiac action potential and at the same time are affected by it. [Na(+)]i is controlled by the balance between Na(+) influx through various pathways, including the Na(+)/Ca(2+) exchanger and Na(+) channels, and Na(+) extrusion via the Na(+)/K(+)-ATPase. [Na(+)]i is elevated in HF due to a combination of increased entry through Na(+) channels and/or Na(+)/H(+) exchanger and reduced activity of the Na(+)/K(+)-ATPase. Here we review the major Na(+) transport pathways in cardiac myocytes and how they participate in regulating [Na(+)]i in normal and failing hearts. This article is part of a Special Issue entitled "Na(+) Regulation in Cardiac Myocytes."
authors.affiliation: Department of Pharmacology, University of California, Davis, CA, USA. sdespa@ucdavis.edu
authors.forename: Sanda
authors.initials: S
authors.lastname: Despa
authors.forename: Donald M
authors.initials: DM
authors.lastname: Bers
mesh_terms: D000200:Action Potentials; D000818:Animals; D001692:Biological Transport; D006333:Heart Failure / Q000378:metabolism* / Q000503:physiopathology; D006801:Humans; D009200:Myocardial Contraction; D032383:Myocytes, Cardiac / Q000378:metabolism; D012964:Sodium / Q000378:metabolism*; D019831:Sodium-Calcium Exchanger / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D061566:Voltage-Gated Sodium Channels / Q000378:metabolism
chemical_list: D019831:Sodium-Calcium Exchanger; D061566:Voltage-Gated Sodium Channels; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase
keywords: AP; Ca(2+)/calmodulin dependent kinase II; CaMKII; DAD; FXYD; Heart failure; Intracellular Na(+) concentration; Myocyte; NBC; NCX; NHE; NKA; Na(+)/Ca(2+) exchanger; Na(+)/H(+) exchanger; Na(+)/HCO(3)(−) cotransporter; Na(+)/K(+)-ATPase; PLM; RyR; SR; TM; [Ca(2+)](i); [Ca(2+)](m); [Na(+)](i); action potential; concentration of free Ca(2+) in the cytosol; concentration of free Ca(2+) in the mitochondrial matrix; delayed afterdepolarization; family of proteins that are specific Na/K-ATPase regulators; intracellular Na(+) concentration; phospholemman; ryanodine receptor; sarcoplasmic reticulum; transmembrane domain