© 1995 by European Society of Cardiology
Copyright © 1995, European Society of Cardiology
Combined therapy with dimethylthiourea, diltiazem and amiloride/dimethylamiloride in the ischemic/reperfused heart
bieta Czarnowskab
aDepartment of Clinical Physiology, Medical Centre of Postgraduate Education, Marymoncka 99, 01-813 Warszawa, Poland
bDepartment of Pathomorphology, Child Health Center, Al. Dzieci Polskich 20, 04-736 Warszawa, Poland
* Corresponding author. Tel. (+48-22) 340367; Fax (+48-22) 340470.
Objectives: The relative contribution of oxygen free radicals, disturbances in calcium homeostasis and Na+/H+ exchange in the development of injury in the ischemic/reperfused bean was investigated. The study was designed to assess whether these factors initiate independent mechanisms of injury or, alternatively, they share a common mechanism of toxicity. Methods: Isolated working rat hearts were subjected to different periods (30–55 min) of global ischemia and then were reperfused for 30 min. We compared the effects of oxygen radical scavengers (10 mM dimethylthiourea, DMTU and 0.6 mM desferrioxamine), inhibitors of Na+/H+ exchange (0.15 mM amiloride and 15 µM dimethylamiloride, DMA) and of 0.1 µM diltiazem, which was used to limit calcium overload, given alone or in combination, on the rate of myocardial injury development (recovery of hemodynamic function, LDH release, incidence of severe arrhythmias and structural integrity of cardiomyocytes were estimated at reperfusion following different periods of ischemia). Results: All interventions studied, when given alone, provided nearly equivalent cardioprotection. DMTU or desferrioxamine when applied in combination with diltiazem provided additive cardioprotection, relatively limited, however, as compared to the remarkable cardioprotection achieved by DMTU or desferrioxamine in combination with amiloride. Conclusions: All mechanisms studied may contribute in an equal manner to the rate of injury development in the ischemic/reperfused heart. The oxygen free radicals-induced myocardial injury may be partially attributed to some disturbance in intracellular calcium homeostasis, possibly calcium overload, whereas the damaging effect of the Na+/H+ exchange activated upon reperfusion is probably largely related to some other mechanism.
KEYWORDS Myocardial ischemia; Reperfusion; Free radicals; Calcium overload; Na+/H+ exchange; Dimethylthiourea; Amiloride; Dimethylamiloride; Morphology; Rat heart; Calcium antagonists
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