[Analysis of the interaction between nicotinic acetylcholine receptor and Na+,K(+)-ATPase in the rat skeletal muscle and the Torpedo electric organ membrane preparation].
The interaction between the nicotinic acetylcholine receptor and Na+,K(+)-ATPase described previously was further studied in isolated rat diaphragm and in a membrane preparation of Torpedo californica electric organ. Three specific agonists of the nicotinic receptor: acetylcholine, nicotine and carbamylcholine (100 nmol/L each), all hyperpolarized the non-synaptic membranes of muscle fibers by up to 4 mV. Competitive antagonists of nicotinic acetylcholine receptor, d-tubocurarine (2 mcmol/L) or alpha-bungarotoxin (5 nmol/L) completely blocked the acetylcholine-induced hyperpolarization indicating that the effect requires binding of the agonists to their specific sites. The noncompetitive antagonist, proadifen (5 mcmol/L), exerted no effect on the amplitude of hyperpolarized but decreased K0.5 for this effect from 28.3 +/- 3.6 nmol/L to 7.1 +/- 2.3 nmol/L. Involvement of the Na+,K(+)-ATPase was suggested by data demonstrating that three specific Na+,K(+)-ATPase inhibitors: ouabain, digoxin or marinobufagenin (100 nmol/L each), all inhibit the hyperpolarizing effect of acetylcholine. Acetylcholine did not affectation either the catalytic activity of the Na+,K(+)-ATPase purified from sheep kidney or the transport activity of the Na+,K(+)-ATPase in the rat erythrocytes, i. e. in preparations not containing acetylcholine receptors. Hence, acetylcholine does not directly affect the Na+,K(+)-ATPase. In a Torpedo membrane preparation, ouabain (< or = 100 nmol/L) increased the binding of the fluorescent ligand: Dansyl-C6-choline (DCC). No ouabain effect was observed either when the agonist binding sites of the receptor were occupied by 2 mmol/L carbamylcholine, or in the absence Mg2+, when the binding of ouabain to the Na+,K(+)-ATPase is negligible. These results indicate that ouabain only affects specific DCC binding and only when bound to the Na+,K(+)-ATPase. The data obtained suggest that, in two different systems, the interaction between the nicotinic acetylcholine receptor and the Na+,K(+)-ATPase specifically involve the ligand binding sites of these two proteins.
Krivoĭ
I I
II
Drabkina
T M
TM
Vasil'ev
A N
AN
Kravtsova
V V
VV
Mandel
F
F
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D001692:Biological Transport; D002018:Bufanolides / Q000494:pharmacology; D002384:Catalysis; D002462:Cell Membrane / Q000502:physiology; D003619:Dansyl Compounds / Q000737:chemistry; D003964:Diaphragm / Q000502:physiology; D004077:Digoxin / Q000494:pharmacology; D004557:Electric Organ / Q000502:physiology* / Q000648:ultrastructure; D004912:Erythrocytes / Q000378:metabolism; D008024:Ligands; D008274:Magnesium / Q000502:physiology; D008297:Male; D008564:Membrane Potentials; D018482:Muscle, Skeletal / Q000502:physiology*; D009538:Nicotine / Q000494:pharmacology; D018722:Nicotinic Agonists / Q000494:pharmacology; D018733:Nicotinic Antagonists / Q000494:pharmacology; D010042:Ouabain / Q000494:pharmacology; D000644:Quaternary Ammonium Compounds / Q000737:chemistry; D051381:Rats; D011978:Receptors, Nicotinic / Q000502:physiology*; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000502:physiology*; D014101:Torpedo
D002018:Bufanolides; D003619:Dansyl Compounds; D008024:Ligands; D018722:Nicotinic Agonists; D018733:Nicotinic Antagonists; D000644:Quaternary Ammonium Compounds; D011978:Receptors, Nicotinic; C093896:marinobufagenin; D010042:Ouabain; C027933:(1-(5-dimethylaminonaphthalene)sulfonamido)-n-hexanoic acid-beta-N-trimethylammonium ethyl ester; D009538:Nicotine; D004077:Digoxin; D000254:Sodium-Potassium-Exchanging ATPase; D008274:Magnesium; D000109:Acetylcholine