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  • Title: Inhibition of (Na/K)-ATPase by NFE induces an increase in mechanical activity of perfused guinea-pig heart.
    Author: Vrbanová A, Stankovicová T, Docolomanský P, Stefko I, Ziegelhöffer A, Breier A.
    Journal: Gen Physiol Biophys; 1994 Oct; 13(5):433-41. PubMed ID: 7797051.
    Abstract:
    The effect of 1-(5-nitro-2-furyl)-2-(phenylsulfonyl)-2-(furylcarbonyl)- ethylene (NFE) on stimulation of (Na/K)-ATPase by sodium and potassium ions was tested in isolated, partially purified sarcolemmal preparation from guinea-pig hearts. NFE inhibited competitively the stimulation of the enzyme by increasing concentrations of potassium. This inhibition was characterized by a significant (p < 0.001) increase of the K0.5 value, a considerable decrease of the Hill's cooperativity constant n as well as by an insignificant diminution of the Vmax value. Contrary to the effect on stimulation by potassium, NFE inhibited non-competitively the stimulation of the ATPase by sodium ions with a significant (p < 0.001) depression of Vmax but without any considerable effect on the K0.5 and n values. These results indicated that NFE may interact with the molecule of (Na/K)-ATPase in a locus close to or identical with the potassium binding site of the enzyme, i.e., in a similar mode as it was well documented for ouabain. This possibility was strongly supported by the finding that NFE administered at the concentration of 0.1 mumol/l in the perfusion medium increased significantly (p < 0.01) the mechanical activity of isolated perfused guinea-pig heart (Langendorff preparation). Nevertheless, it also caused some adverse effects such as a slight increase in coronary flow resistance and in heart rate as well as in the left ventricular end-diastolic pressure.(ABSTRACT TRUNCATED AT 250 WORDS)
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