Calcium ion binding to lobster nerve membranes.
The binding of 45Ca2+ to membrane material isolated from lobster walking leg nerves was studied using a rapid filtration technique. In solutions of high ionic strength (450 mM), the amount of 45Ca2+ bound to this membrane material was found to be highly dependent on the monovalent cation used in the incubating solution. The amount of 45Ca2+ bound was larger when the membranes were incubated in a KCl solution compared to when they were incubated in a NaCl solution. This difference was attributed to the ability of these closed membrane vesicles to accumulate Ca2+ into the vesicle when incubating in a KCl solution but not in a NaCl solution. This accumulation of Ca2+ was found to be independent of metabolic energy and depended primarily on the absence of Na+ from the incubation medium. At low ionic strength, the membranes formed open fragments and the amount of Ca2+ bound was no longer sensitive to the monovalent cation species in the incubation solution. The 45Ca2+ bound under these low ionic strength conditions was considered to be bound to anionic sites on the membranes.
D000818:Animals; D001665:Binding Sites; D002118:Calcium / Q000378:metabolism*; D002414:Cations, Monovalent / Q000494:pharmacology; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism*; D007700:Kinetics; D008121:Nephropidae; D009474:Neurons / Q000378:metabolism* / Q000648:ultrastructure; D009994:Osmolar Concentration; D012530:Saxitoxin / Q000494:pharmacology; D013347:Subcellular Fractions / Q000648:ultrastructure
D002414:Cations, Monovalent; D012530:Saxitoxin; D002118:Calcium