Sodium extrusion by internally dialyzed squid axons.
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 (mM): 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.
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001120:Arginine / Q000378:metabolism; D001369:Axons / Q000378:metabolism*; D002297:Cardanolides / Q000494:pharmacology; D003593:Cytoplasm; D003956:Dialysis / Q000295:instrumentation*; D004558:Electric Stimulation; D008974:Mollusca; D010539:Permeability; D011188:Potassium / Q000378:metabolism; D011194:Potassium Isotopes; D012964:Sodium / Q000378:metabolism*; D012975:Sodium Isotopes
D002297:Cardanolides; D011194:Potassium Isotopes; D012975:Sodium Isotopes; D000255:Adenosine Triphosphate; D001120:Arginine; D012964:Sodium; D011188:Potassium