Ion selectivity of the nerve membrane sodium channel incorporated into liposomes.
Tetrodotoxin-sensitive sodium channels of lobster nerve membranes were incorporated into soybean liposomes by the freeze-thaw-sonication procedure and their ionic selectivity was studied. Veratridine and grayanotoxin-I were used to activate the sodium channels and the increment of the ionic flux through them was specifically abolished by tetrodotoxin. The drug-sensitive 22Na+, 42K+, 86Rb+ and 137Cs+ influxes were measured. The permeability ratios calculated directly from ion fluxes showed that the channels preferably allow the passage of Na+. No anion influx ([32P]phosphate, [35S]sulfate, 36Cl) sensitive to the drugs was observed. The data reveal that the sodium channels incorporated into liposomes remain cation-selective and discriminate among different cations.
D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D002712:Chlorides / Q000378:metabolism; D007473:Ion Channels / Q000187:drug effects / Q000378:metabolism*; D008081:Liposomes; D008121:Nephropidae; D009474:Neurons / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism; D012413:Rubidium / Q000378:metabolism; D012964:Sodium / Q000378:metabolism*; D013779:Tetrodotoxin / Q000494:pharmacology
D002712:Chlorides; D007473:Ion Channels; D008081:Liposomes; D013779:Tetrodotoxin; D012964:Sodium; D012413:Rubidium; D011188:Potassium