[Does altered regulation of Na+ cause reduced myocardial contractility in heart failure?].
BACKGROUND
Cardiac contractility is largely regulated through transients in intracellular Ca2+ concentration [Ca2+]i. [Ca2+]i is under the influence of the sarcolemmal Na+/Ca2+ exchanger that exchanges Ca2+ for Na+ and which is mainly regulated by the intracellular Na+ concentration ([Na+]i). Consequently, [Na+]i influences cardiac contractility. [Na+]i is regulated by numerous proteins: Na+/K+ adenosine triphosphatases (ATPases), Na+-channels and Na+/H+ exchangers that control and are controlled by [Na+]i. In particular, the Na+/K+ ATPase and its crosstalk with the other proteins controls the intracellular level of Na+.


METHODS
This review focuses on the significance of an efficient crosstalk between the topical proteins for control of [Na+]i.


RESULTS
Co-localised proteins will sense the same [Na+]i; this is important as [Na+]i seems to vary in different parts of the cell. Evidence suggests that the regulation of [Na+]i is altered in heart failure. Several transport proteins have altered activity and expression patterns and this could partially explain the reduced contractility in heart failure.


CONCLUSIONS
A better understanding of the control of [Na+]i may lead to a new therapy for heart failure.
Swift
Fredrik
F
Institutt for eksperimentell medisinsk forskning, Universitetet i Oslo. fredrik.swift@ioks.uio.no
Sjaastad
Ivar
I
Sejersted
Ole M
OM
D015220:Calcium Channels / Q000737:chemistry / Q000378:metabolism / Q000502:physiology; D002352:Carrier Proteins / Q000737:chemistry / Q000378:metabolism / Q000502:physiology; D006333:Heart Failure / Q000378:metabolism / Q000503:physiopathology*; D006801:Humans; D015394:Molecular Structure; D009200:Myocardial Contraction / Q000502:physiology*; D009206:Myocardium / Q000378:metabolism; D015222:Sodium Channels / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D000254:Sodium-Potassium-Exchanging ATPase / Q000737:chemistry / Q000378:metabolism / Q000502:physiology
D015220:Calcium Channels; D002352:Carrier Proteins; D015222:Sodium Channels; D000254:Sodium-Potassium-Exchanging ATPase