A second, slower inactivation process in acetylcholine receptor-rich membrane vesicles prepared from Electrophorus electricus.
An agonist such as carbamylcholine or phenyltrimethylammonium induced a second, slower complete inactivation of acetylcholine receptor prepared from Electrophorus electricus. The rate of this inactivation of the receptor followed first-order kinetics. The rate constant of the inactivation increased with the agonist concentration until it reached a plateau, the value of which was 0.19 h-1 at 4.5 degrees C. The reaction was also temperature dependent, and the activation energy of the inactivation caused by 1 mM carbamylcholine was estimated to be 7.6 kcal/mol. The inactive receptor was reconverted to the active form with a rate constant of about 0.015 h-1 at 4.5 degrees C when the carbamylcholine concentration (0.1 mM) was reduced by 15-fold dilution in eel Ringer's solution. These results can be interpreted by adding, to the minimal reaction scheme proposed by the Hess group, a second, slower, reversible inactivation process either through the intact form or through the first desensitized form of the receptor binding two agonist molecules.
D000818:Animals; D002217:Carbachol / Q000494:pharmacology*; D055598:Chemical Phenomena; D002621:Chemistry; D004557:Electric Organ; D004593:Electrophorus; D066298:In Vitro Techniques; D007700:Kinetics; D008433:Mathematics; D008956:Models, Chemical; D000644:Quaternary Ammonium Compounds / Q000494:pharmacology*; D011950:Receptors, Cholinergic / Q000187:drug effects*; D013997:Time Factors
D000644:Quaternary Ammonium Compounds; D011950:Receptors, Cholinergic; C009571:phenyltrimethylammonium; D002217:Carbachol