The Role of Na-Ca Exchange in Heart
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.
KeywordsMembrane Potential Cardiac Cell Squid Giant Axon Squid Axon Gradient Difference
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- 5.Mullins LJ: Ion Transport in Heart. Raven Press, New York, 1981.Google Scholar
- 12.Eisner DA, Lederer WJ, Vaughan-Jones R: The dependence of sodium pumping and tension on intracellular sodium activity in voltage-clamped sheep Purkinje fibres. J Physiol (Lond) 317: 163–187, 1981.Google Scholar
- 13.Mullins LJ: The generation of electric currents in cardiac fibers by Na/Ca exchange. Am J Physiol 263: C103–C110, 1979.Google Scholar