Thermodynamic studies with acetylthiocholine on nicotinic receptors of mammalian skeletal muscle in vitro.
The temperature dependency of binding of acetylthiocholine, a specific nicotinic agonist, to the nicotinic receptor of mammalian skeletal muscle was studied using isotonic contractions of the rat denervated diaphragm preparation in vitro. The dissociation constants at different temperatures (22-39 degrees) were determined by the Furchgott method using alpha-bungarotoxin as an irreversible antagonist. Both free energy of association (delta G zero = -22.93 kJ/mol at 37 degrees) and enthalpy of binding (delta H zero = -58.35 kJ/mol) calculated from Kd (dissociation constant) and slope of lnKd versus 1/T (van't Hoff plot) respectively were found to be negative. The negative entropy value (delta S zero = -0.113 kJ/mol/deg) obtained from the intercept of this van't Hoff plot differs from the large positive value obtained earlier employing radioligand binding studies of the nicotinic receptor of Electrophorus electricus.
Banerjee
B
B
Division of Pharmacology and Experimental Therapeutics, Indian Institute of Chemical Biology, Calcutta.
Ganguly
D K
DK
D000122:Acetylthiocholine / Q000494:pharmacology*; D000818:Animals; D002038:Bungarotoxins / Q000494:pharmacology; D066298:In Vitro Techniques; D007551:Isotonic Contraction; D009132:Muscles / Q000378:metabolism*; D018722:Nicotinic Agonists; D051381:Rats; D017207:Rats, Sprague-Dawley; D013696:Temperature; D013816:Thermodynamics
D002038:Bungarotoxins; D018722:Nicotinic Agonists; D000122:Acetylthiocholine