Effects of the type-1 Na+/H+-exchange inhibitor cariporide (Hoe 642) on cardiac tissue |
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Authors: | S Dhein Kathi Krüsemann Frank Engelmann Michaela Gottwald |
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Institution: | (1) Institute of Pharmacology, University of Cologne, Gleueler Strasse 24, D-50931 Cologne, Germany, DE |
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Abstract: | Ischemia leads to intracellular acidification which can be counteracted by the Na+/H+-exchange mechanism. A blockade of this exchanger has been hypothesized to cause stronger intracellular acidification in the
course of ischemia thereby protecting the heart from ischemic damage. The aim of our study was to find out (1) whether in
the course of ischemia areas become electrically silent, (2) whether this is enhanced by the Na+/H+-exchange inhibitor cariporide (4-Isopropyl-3-methylsulfonylbenzoyl-guanidine; Hoe 642) and whether cariporide has protective
effects. Therefore, we submitted isolated rabbit hearts, perfused according to the Langendorff technique to regional ischemia
(LAD occlusion) for 30 min followed by 30 min reperfusion with (n=7) or without (n=7) pre-treatment with 1 μM cariporide. Under these conditions 256-channel epicardial potential mapping was carried out. Under
non-ischemic conditions cariporide did not alter any of the parameters under observation. We found that ischemia led to marked
alterations of the activation pattern, to action potential shortening and a marked increase in the dispersion of refractoriness.
In the ischemic region there was a significant ST deviation from the isoelectrical line (control 32±10; 30 min ischemia: 290±35
arbitrary units a.u.]). This was markedly reduced by cariporide (control 39±10; 30 min ischemia: 170±25 a.u.). The increase
in dispersion by ischemia (by 50±5 ms) was significantly counteracted by cariporide (increased dispersion by 20±4 ms). In
a similar way the alteration of the activation pattern was antagonized. Under the influence of cariporide we found a lower
increase in the left ventricular enddiastolic pressure, and a significantly slower recovery of the action potential duration.
After 30 min of ischemia 24±5 (control series) 24.5±5 mm2 (cariporide) became electrically silent. In a second series of experiments the incidence of arrhythmia was assessed: we found
ventricular fibrillation in 6/7 untreated control hearts and in 4/7 cariporide treated hearts. In a third series of experiments
we determined the intracellular ATP] after 30 min of LAD occlusion using a histochemical method. We observed a decrease in
ATP] in the ischemic region as compared to the non-ischemic right ventricular wall, which was less pronounced in cariporide-treated
hearts. Thus, we conclude that (1) cariporide protects the heart from ischemic damage and (2) at least under these conditions
an enlargement of the electrically silent area did not occur.
Received: 8 August 1997 / Accepted: 23 March 1998 |
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Keywords: | Hoe 642 Cariporide Na+-H+-Exchange Intracellular pH Cardiac ischemia Reperfusion Epicardial mapping Arrhythmia |
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