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. 1962 May;2(3):257–274. doi: 10.1016/s0006-3495(62)86854-4

Sodium and Potassium Ion Effluxes from Squid Axons under Voltage Clamp Conditions

L J Mullins, W J Adelman Jr, R A Sjodin
PMCID: PMC1366371  PMID: 14477156

Abstract

Squid giant axons loaded with Na24 were subjected to short duration (0.5 msec.) clamped depolarizations of about 100 mv at frequencies of 20/sec. and 60/sec. while in choline sea water. Under such conditions the early outward current was just about maximal at the time of termination of the clamping pulse. An integration of the early current versus time record gave 1.2 μcoulomb/cm2 pulse, while a measurement of the extra Na24 efflux resulting from repetitive pulsing gave a charge transfer of 1.4 μcoulomb/cm2 pulse. In sodium-containing sea water and with pulses 50-75 mv more positive than ENa the Na24 efflux is about 3 times the measured charge transfer. The efflux of K42 from a previously loaded axon into normal sea water is only 50 per cent of the measured charge transfer when the membrane is held for about 5 msec. at a potential such that there is no early current, and such pulses are at 10-20/sec. The experiments appear to confirm the suggestion that the early current during bioelectric activity is sodium but provide unsatisfactory support for the identification of the delayed but sustained current solely with potassium ions. Resting Na+ efflux is 0.6 pmole/cm2 sec. mmole [Na]1, while the apparent K+ efflux is about 250 pmole/cm2 sec. and is little affected by hyperpolarization.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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