Abstract
Electrogenic Na-Ca exchange has been known to act in the cardiac sarcolemma as a major mechanism for extruding Ca ions1–3. Ionic flux measurements in cardiac vesicles have recently suggested that the exchange ratio is probably 3 Na:l Ca (refs 4, 5), although a membrane current generated by such a process has not been isolated. Using the intracellular perfusion technique6,7 combined with the whole-cell voltage clamp8, we were able to load Na+ inside and Ca2+ outside the single ventricular cells of the guinea pig and have succeeded in recording an outward Na-Ca exchange current while blocking most other membrane currents. The current is voltage-dependent, blocked by La3+ and does not develop in the absence of intracellular free Ca2+. This report presents the first direct measurement of the cardiac Na-Ca exchange current, and should facilitate the study of Ca2+ fluxes during cardiac activity, together with various electrical changes attributable to the Na-Ca exchange9 and the testing of proposed models10–12.
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Kimura, J., Noma, A. & Irisawa, H. Na-Ca exchange current in mammalian heart cells. Nature 319, 596–597 (1986). https://doi.org/10.1038/319596a0
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DOI: https://doi.org/10.1038/319596a0
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