Abstract
The Na/K pump usually pumps more Na+ out of the cell than K+ in, and so generates an outward component of membrane current1,2 which, in the heart, can be an important modulator of the frequency and shape of the cardiac impulse3–5. Because it is electrogenic, Na/K pump activity ought to be sensitive to membrane potential, and it should decline with hyperpolarization6–9. However, such voltage dependence of outward pump current has yet to be demonstrated6–10, one reason being the technical difficulty of accurately measuring pump current over a sufficiently wide voltage range. The whole-cell patch-clamp technique11 allows effective control of both intracellular and extracellular solutions as well as membrane voltage. Applying this technique to myocardial cells isolated from guinea pig ventricle, we have measured Na/K pump current between −140 mV and +60 mV, after minimizing passive currents flowing through Ca2+, K+ and Na+ channels. We report here that strongly activated pump current shows marked voltage dependence; it declines steadily from a maximal level near 0 mV, becoming very small at −140 mV. Pump current–voltage relationships will provide essential information for testing models of the Na/K pump mechanism and for predicting pump-mediated changes in the electrical activity of excitable cells.
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Gadsby, D., Kimura, J. & Noma, A. Voltage dependence of Na/K pump current in isolated heart cells. Nature 315, 63–65 (1985). https://doi.org/10.1038/315063a0
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DOI: https://doi.org/10.1038/315063a0
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