[Role of the alpha2-isoform of Na+, K(+)-ATPase in the positive inotropic effect of ouabain and marinobufagenin in the rat diaphragm].
It was shown that the specific inhibitors of Na+, K(+)-ATPase ouabain and marinobufagenin increased the contraction of an isolated rat diaphragm (positive inotropic effect) by up to approximately 15% in a dose-dependent manner with EC50 = 1.2 +/- 0.3 and 0.3 +/- 0.1 nM, respectively. The results indicate the involvement of the ouabain-sensitive alpha 2 isoform of Na+, K(+)-ATPase. The analysis of ouabain-resting membrane potential dose-response relationships in the presence and absence of hyperpolarizing concentration of acetylcholine (100 nM) suggests the existence of two pools of alpha 2 Na+, K(+)-ATPase with different affinities for ouabain. The pool with a higher ouabain affinity is involved in the hyperpolarizing effect of acetylcholine and, presumably, in the positive inotropic effect of ouabain, which might be a mechanism of regulation of muscle efficiency by circulating endogenous inhibitors of Na+, K(+)-ATPase.
Krivoĭ
I I
II
Drabkina
T M
TM
Kravtsova
V V
VV
Vasil'ev
A N
AN
Vashchinkina
E V
EV
Prokof'ev
A V
AV
Kubasov
I V
IV
D000818:Animals; D002018:Bufanolides / Q000494:pharmacology*; D003964:Diaphragm / Q000187:drug effects* / Q000502:physiology; D066298:In Vitro Techniques; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000502:physiology; D008297:Male; D008564:Membrane Potentials; D009119:Muscle Contraction / Q000187:drug effects; D010042:Ouabain / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors / Q000502:physiology*; D013268:Stimulation, Chemical
D002018:Bufanolides; D007527:Isoenzymes; C093896:marinobufagenin; D010042:Ouabain; D000254:Sodium-Potassium-Exchanging ATPase