Zusammenfassung
Die Wirkung der extracellulären pH-Erniedrigung (im Bereich von pH 7,3 bis pH 4,0 bei 15°C) auf die Membranströme durch den Ranvierschen Schnürring von Rana esculenta wird unter Voltage-Clamp-Bedingungen untersucht.
Die Strom-Spannungsbeziehungen der Natrium- und Kaliumsysteme werden bei verschiedenen pH-Werten analysiert. Die beiden Systeme werden vergleichend diskutiert.
Die pH- und die Spannungsabhängigkeit der relativen Stromwerte werden durch eine allgemeine Gleichung beschrieben. Diese Gleichung ist jeweils durch vier Parameter für jedes System bestimmt.
Beim Natriumsystem lassen sich die extrapolierten Verhältnisse der Extremwertströme aus den Strom-Spannungskurven (I peak gegenV) durch die Dissoziationskurve einer schwachen Säure mit einem pK von 5,15±0,05 beschreiben. Ferner lassen sich beim Kaliumsystem die Stromverhältnisse bei hohen Depolarisationen auf eine Dissoziationskurve mit einem pK von 4,63±0,05 eintragen.
Summary
The effect of reducing extracellular pH (in the range from pH 7.3 to pH 4.0 at 15°C) on the membrane currents of the Ranvier node dissected from Rana esculenta has been investigated under voltage-clamp conditions. The current-voltage relationships of the sodium and potassium systems are analyzed at different pH values. The two systems are compared.
The pH and voltage dependence of the relative current values of the sodium and potassium systems are described by a general equation. The equation has one set of four parameters for each of the two systems. In the sodium system the extrapolated ratios of the peak currents of the current-voltage curves (I peak vs.V) can be described as a dissociation curve of a weak acid with a pK a of 5.15±0.05 S.D. Furthermore, in the potassium system the current ratios at higher depolarizations can also be plotted on a dissociation curve with a pK a of 4.63±0.05 S.D.
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This investigation was partly sponsored by the Deutsche Forschungsgemeinschaft, Bad Godesberg.
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Drouin, H., The, R. The effect of reducing extracellular pH on the membrane currents of the Ranvier node. Pflugers Arch. 313, 80–88 (1969). https://doi.org/10.1007/BF00586331
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DOI: https://doi.org/10.1007/BF00586331