Summary
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1.
The membrane potential, the tension development and the42K-efflux were studied in the ear artery of the rabbit under different experimental conditions.
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2.
K-free solution depolarized the cells. Readmission of K in the external medium caused a transient hyperpolarization.
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3.
Ouabain 10−5 M also depolarized the cells. On washing out the ouabain the membrane potential gradually returned to its control value.
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4.
Tension development appeared simultaneously with the depolarization, but it subsided during prolonged depolarization.
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5.
K-free solution and ouabain induced a small increase of the rate coefficient of K-efflux from the ear artery. This effect appeared later than the depolarization or the tension development. These changes of42K-efflux make a rapid change of (Na)i unlikely.
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6.
It is concluded that the electrogenic Na-pump plays an important role in maintaining the membrane potential of arterial smooth muscle cells. All procedures which inhibit this pump, induce a depolarization of the cells and thereby a tension development. There is no experimental evidence in favour of the hypothesis that the inhibition of a Na−Ca exchange system would be the primary event in inducing contraction under our experimental conditions.
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Hendrickx, H., Casteels, R. Electrogenic sodium pump in arterial smooth muscle cells. Pflugers Arch. 346, 299–306 (1974). https://doi.org/10.1007/BF00596185
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DOI: https://doi.org/10.1007/BF00596185