The Role of Na-Ca Exchange in Heart

  • Lorin J. Mullins
Part of the Developments in Cardiovascular Medicine book series (DICM, volume 34)


Cardiac muscle cells differ from those of skeletal muscle in many respects; an important difference is that cardiac cells contract when placed in Na-free salines while skeletal muscle fibers do not. Since in many cardiac cells this sort of replacement does not change membrane potential, one must ask what is the signal for contraction produced by a reduction in external Na. It cannot be electrical since membrane potential does not change and, in spite of some rather exotic ideas that have been put forward, the most viable idea is that if Nao is made low, Cao can exchange for Nai and thus a flux of inward moving Ca is generated to provide for a contraction.


Membrane Potential Cardiac Cell Squid Giant Axon Squid Axon Gradient Difference 
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© Springer Science+Business Media Dordrecht 1984

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  • Lorin J. Mullins

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