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KMID : 0382619820020010099
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Hanyang Journal of Medicine
1982 Volume.2 No. 1 p.99 ~ p.110
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Changes in Activities of Cardiac ATPases and RNases in Ouabain Induced Cardiotoxicity
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李正浩/Lee, Jung Ho
金近鎬/高在炅/Kim, Kun Ho/Koh, Jai Kyung
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Abstract
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In order to elucidate the nature of cardiac toxicity induced by ouabain, activities of adenosine triphosphatases (ATPases) in heart and serum from rats treated with. ouabain were determined and they were compared with those from normal rats. Also determined were activities of acid and alkaline RNases from heart and serum from the rats using RNA, poly A or poly C as substrates. The results obtained. were as follows:
1) While the activity of Mg2+ -ATPase in heart homogenate was influenced by neither Na-,-, K+, nor ouabain, a distinct activity for Nat, K+-ATPase was observed in both the heart cell fractions of 104 x g supernatant and precipitate.
2) Activities of Na+, K+-ATPase in both mitochondrial and microsomal fractions? of heart tissues were significanlty decreased in ouabain treated rats as compared with those of control rats. While cardiac Na+ content was significantly increased, Kt content was significantly, decreased.
3) In in vitro experiments the activity of cardiac Mgt+-ATPase was not influenced. by ouabain added to the assay medium, but Mg 2+-ATPase activities in heart. homogenate and the cell fractions were :decreased in rats treated with ouabain, as compared with those in control rats. These results indicate that the administration of ouabain leads to changes in myocardial Nat and K+ contents? by inhibiting mitochondrial and microsomal Na+ and. K+ contents by inhibiting mitochondrial and microsomal Na+, K+-ATPase activities, which may in turn, result in the disturbance of myocardial contractility to induce cardiac toxicity. It can not be ruled out, however, the possibility that a decrease in. cardiac Mgz+-ATPase activity may be correlated, in part, with cardiotoxicity induced by ouabain.
4) Activities. of cardiac acid RNase was significantly decreased when measured. using RNA as the substrate and was increased using poly C as the substrate in rats treated with ouabain as compared with those in control rats. On the other hand, activities of cardiac alkaline RNase was significantly decreased when measured using RNA or poly A as the substrate. These results suggest that the administration of ouabain leads to damages in structural integrity of myocardium.
5) The mean values of activities of serum ATPases and RNases appeared to be higher in rats treated with ouabain than in control rats, but exhibited no statistical significance. The results mean that in ouabain cardiotoxicity the cardiac tissue enzymes may not be released into the blood stream or the amount of tissue enzymes released into the blood may not be large enough for giving rise significant changes in activities of the serum enzymes.
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