Sodium Extrusion by Internally Dialyzed Squid Axons

F. J. Brinley; L. J. Mullins

doi:10.1085/jgp.50.10.2303

$A method has been developed which allows a length of electrically excitable squid axon to be internally dialyzed against a continuously flowing solution of defined composition. Tests showed that diffusional exchange of small molecules in the axoplasm surrounding the dialysis tube occurred with a half-time of 2–5 min, and that protein does not cross the wall of the dialysis tube. The composition of the dialysis medium was (m M ): K isethionate 151, K aspartate 151, taurine 275, MgCI 2 4–10, NaCl 80, KCN 2, EDTA 0.1, ATP 5–10, and phosphoarginine 0–10. The following measurements were made: resting Na influx 57 pmole/cm 2 sec ( n = 8); resting potassium efflux 59 pmole/ cm 2 sec ( n = 4); stimulated Na efflux 3.1 pmole/cm 2 imp ( n = 9); stimulated K efflux 2.9 pmole/cm 2 imp ( n = 3); resting Na efflux 48 pmole/cm 2 sec ( n = 18); Q 10 Na efflux 2.2 ( n = 5). Removal of ATP and phosphoarginine from the dialysis medium ( n = 4) or external application of strophanthidin ( n = 1) reversibly reduced Na efflux to 10–13 pmole/cm 2 sec. A general conclusion from the study is that dialyzed squid axons have relatively normal passive permeability properties and that a substantial fraction of the Na efflux is under metabolic control although the Na extrusion mechanism may not be working perfectly. Footnotes Submitted: 27 March 1967$

Sodium Extrusion by Internally Dialyzed Squid Axons

Brinley, F. J.; Mullins, L. J.

Follow The Journal of General Physiology , Volume 50 (10): 2303 Rockefeller University Press – Nov 1, 1967