Biophysical Journal 2: 257-274 (1962)
© 1962 the Biophysical Society

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Mullins, L. J. Articles by Sjodin, R. A. Search for Related Content PubMed PubMed Citation Articles by Mullins, L. J. Articles by Sjodin, R. A.

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

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 E_Na 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.

This article has been cited by other articles:

				W. J. Adelman Jr., F. M. Dyro, and J. P. Senft Internally Perfused Axons: Effects of Two Different Anions on Ionic Conductance Science, March 18, 1966; 151(3716): 1392 - 1394. [Abstract] [PDF]