Inhibition of (Na/K)-ATPase by electrophilic substances: Functional implications |
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| Authors: | Albert Breier Attila Ziegelhöffer Tania Stankovičová Peter Dočolomanský Peter Gemeiner Alena Vrbanová |
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| Affiliation: | (1) Institute of Molecular Physiology and Genetics, Slovak Academy of Sciences, Dúbravská cesta 9, 842 38 Bratislava, Slovak Republic;(2) Institute for Heart Research, Slovak Academy of Sciences, 842 38 Bratislava, Slovak Republic;(3) Institute of Chemistry, Slovak Academy of Sciences, 842 38 Bratislava, Slovak Republic;(4) Present address: Faculty of Pharmacy, Department of Pharmacology and Toxicology, Comenius University, Bratislava, Slovak Republic |
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| Abstract: | The effect of electrophilic substances: p-bromophenylisothiocyanate (PBITC); fluoresceinisothiocyanate (FITC); [4-isothiocyanatophenyl-(6-thioureidohexyl)-carbamoylmethyl]-ATP (ATPITC); 2,4,6-trinitrobezenesulfonic acid (TNBS); 1-(5-nitro-2-furyl)-2-phenylsulfonyl-2-furylcarbonyl ethylene (FE1); 1-(5-phenylsulfonyl-2-furyl)-2-phenylsulfonyl-2-furylcarbonyl ethylene (FE2) and 1-(5-phenylsulfonyl-2-furyl)-2-phenylsulfonyl-2-tienocarbonyl ethylene (FE3) on the sarcolemmal (Na/K)-ATPase isolated from guinea-pig hearts was studied. FITC and PBITC were found to inhibit competitively the activation of (Na/K)-ATPase by ATP. Being for the enzyme inhibitor and substrate at the same time ATPITC does not offered clear kinetic behavior. However, the activation of (Na/K)-ATPase by sodium and potassium ions was inhibited non-competitively by all three isothiocyanates. These data indicated that isothiocyanates may interact predominantly in the ATP-binding site of the enzyme molecule. In contrary to isothiocyanates TNBS and FE1 (FE2 and FE3 were ineffective) inhibited the activation of (Na/K)-ATPase by ATP non-competitively i.e., their interaction in the ATP-binding site seemed to be improbable. Nevertheless, TNBS and FE1 both manifested affinities to that moiety of (Na/K)-ATPase molecule which is binding potassium. More specific was the effect of FE1 that showed clearly competitive inhibition of potassium-stimulation of the enzyme activity. FE1 exerted also an ouabain-like effect on the mechanical activity of isolated perfused guinea-pig heart. This result indicates that FE1 seems to exert a selective inhibition of the (Na/K)-ATPase not only in vitro but also in integrated cardiac tissue.Abbreviations and symbols PBITC p-bromophenylisothiocyanate - FITC fluoresceinisothiocyanate - ATPITC [4-isothiocyanatophenyl-(6-thioureidohexyl)-carbamoylmethyl]-ATP - TNBS 2,4,6-trinitrobenzenesulfonic acid - FE1 1-(5-nitro-2-furyl)-2-phenylsulfonyl-2-furylcarbonyl ethylene - FE2 1-(5-phenylsulfonyl-2-furyl)-2-phenylsulfonyl-2-furylcarbonyl ethylene - FE3 1-(5-phenylsulfonyl-2-furyl)-2-phenylsulfonyl-2-tienocarbonyl ethylene - DMSO dimethylsufoxide |
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| Keywords: | (Na/K)-ATPase electrophilic reagents cation binding site isolated perfused heart 5-nitrofurylethylene |
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