title: Reconstitution of carbamylcholine-dependent sodium ion flux and desensitization of the acetylcholine receptor from Torpedo californica.
abstract: Membranes rich in acetylcholine receptor were isolated from Torpedo californica by a modification of the procedure of Sobel et al. (Sobel, A., Weber, M., and Changeux, J.-P. (1977) Eur. J. Biochem. 80, 215-224). The receptor was extracted with 2% potassium cholate in the presence of 2.5% soybean phospholipids. After reconstitution by the cholate dialysis procedure, the vesicles exhibited a rapid, carbamylcholine-dependent uptake of 22Na+, which was inhibited by alpha-bungarotoxin and several other known inhibitors. At concentrations above 5 x 10(-5) M carbamylcholine, the fast phase of Na+ influx lasted less than 10 sec. At 5 x 10(-6)M, it lasted 30 sec but was only about 50% of the maximal total uptake observed at optimal agonist concentration. The phenomenon of desensitization was exhibited by the reconstituted vesicles. When 2 x 10(-4)M carbamylcholine was added, 15 sec before 22Na+, the rapid Na+ influx phase was no longer observed.
mesh_terms: D000109:Acetylcholine / Q000378:metabolism; D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D002038:Bungarotoxins / Q000494:pharmacology; D002217:Carbachol / Q000494:pharmacology*; D002462:Cell Membrane / Q000378:metabolism; D004229:Dithiothreitol / Q000494:pharmacology; D004557:Electric Organ / Q000378:metabolism*; D005399:Fishes; D007700:Kinetics; D011950:Receptors, Cholinergic / Q000187:drug effects / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism*
chemical_list: D002038:Bungarotoxins; D011950:Receptors, Cholinergic; D002217:Carbachol; D012964:Sodium; D000109:Acetylcholine; D004229:Dithiothreitol