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Circulation. 1999 Nov 30;100(22):2260-6.

Classic preconditioning decreases the harmful accumulation of nitric oxide during ischemia and reperfusion in rat hearts.

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  • 1Departments of Biochemistry, Albert Szent-Györgyi University, Szeged, Hungary.

Abstract

BACKGROUND:

The role of NO in the mechanism of preconditioning is not understood. Therefore, we studied the effect of preconditioning and subsequent ischemia/reperfusion on myocardial NO content in the presence of an NO synthase (NOS) inhibitor.

METHODS AND RESULTS:

Isolated working rat hearts were subjected to preconditioning protocols of 3 intermittent periods of rapid pacing or no-flow ischemia of 5 minutes' duration each followed by a test 30 minutes of global no-flow ischemia and 15 minutes of reperfusion. Test ischemia/reperfusion resulted in a deterioration of myocardial function and a considerable increase in cardiac NO content as assessed by electron spin resonance. Preconditioning improved postischemic myocardial function and markedly decreased test ischemia/reperfusion-induced NO accumulation. In the presence of 4.6 micromol/L N(G)-nitro-L-arginine (LNA), basal cardiac NO content decreased significantly, although test ischemia/reperfusion-induced functional deterioration and NO accumulation were not affected in nonpreconditioned hearts. However, the protective effects of preconditioning on both test ischemia/reperfusion-induced functional depression and NO accumulation were abolished. When 4.6 micromol/L LNA was administered after preconditioning, it failed to block the effect of preconditioning. In the presence of 46 micromol/L LNA, ischemia/reperfusion-induced NO accumulation was significantly decreased and postischemic myocardial function was improved in nonpreconditioned hearts.

CONCLUSIONS:

Our results show that (1) although NO synthesis by the heart is necessary to trigger classic preconditioning, preconditioning in turn attenuates the accumulation of NO during ischemia/reperfusion, and (2) blockade of ischemia/reperfusion-induced accumulation of cardiac NO by preconditioning or by an appropriate concentration of NOS inhibitor alleviates ischemia/reperfusion injury as demonstrated by enhanced postischemic function.

PMID:
10578001
[PubMed - indexed for MEDLINE]
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