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KMID : 0382619830030010073
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Hanyang Journal of Medicine
1983 Volume.3 No. 1 p.73 ~ p.86
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Properties of Adenosine Triphosphatase in Rat Heart
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吳哲洙/Oh, Chull Soo
金近鎬/高在炅/Kim, Kun Ho/Koh, Jai Kyung
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Abstract
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In the present study a cell fraction which exhibited a distinct activity of Na+, K+ATPase was isolated in rat heart by sodium dodecyl sulfate (SDS) treatment and centrifugation. Properties of cardiac Na+, K+-ATPase were studied using the cell fraction isolated and the results obtained were as follows:
1) After the treatment of the enzyme preparation with SDS, activities of Na+, K+ -ATPase were observed in all the cell fractions including homogenate, the highest activity being found in SDS-104 xg supernatant fraction of heart.
2) Cardiac Mgt + + Na+, K+ -ATPase in the rat exhibited the highest activity against ATP and the lowest activity against pyrimidine ribonucleotides, the decreasing order of the activity being that measured with ATP, GTP, CTP and UTP, respectively. Studies on substrate specificity for cardiac ATPase revealed that nucleoside triphosphatases other than ATPase might be present in heart tissue of rat.
3) The activity of cardiac Na+, K+ -ATPase was found to be stimulated synergistically by Na+ and K+, and the degree of inhibition of the enzyme activity by ouabain was influenced by changes in the cocentrations of monovalent cations added to the incubation medium. The results suggested that inotropic effect of ouabain on the myocardium could be modified by changes in the concentrations of Na+ and K+.
4) The activity of cardiac Na+, K+-ATPase was inhibited by para-hydroxy mercuribenzoate (PHMB) which has been known as a compound exhibiting both the inhibiting effect of sulfhydryl reagents and positive inotropic effect, and the inhibition by PHMB was reversed by a sulfhydryl compound, glutathione. The results confirmed that there was a close relationship between the increase in myocardial contractility and inhibition of the activity of Na+, K+ -ATPase.
5) The activity of cardiac Na+, K+ -ATPase was inhibited by amiodarone, an antiarrhythmic drug with no inotropic action, and mechanism of inhibitory action of amiodarone on the enzyme appeared to be different from that of ouabain.
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