Accumulation of extracellular ATP protects against acute reperfusion injury in rat heart endothelial cells

Objective: Ischemia-reperfusion provokes barrier failure of the coronary microvasculature, leading to myocardial edema development that jeopardizes functional recovery of the heart during reperfusion. Here, we tested whether adenosine 5 '-triphosphate (ATP), either exogenously applied or spontaneously released during reperfusion, protects the endothelial barrier against an imminent reperfusion injury and whether interventions preventing ATP breakdown augment this protective ATP effect. Methods: Cultured microvascular coronary endothelial monolayers and isolated-perfused hearts of rat were used. Results: After ischemic conditions were induced, reperfusion of endothelial monolayers activated the endothelial contractile machinery and caused intercellular gap formation. It also led to the release of ATR When its breakdown was inhibited by 6-N,N-diethyl-beta, gamma-dibromomethylene-D-ATP (ARL 67156; 100 mu M), a selective ectonucleotidase inhibitor, contractile activation and gap formation were significantly reduced. Reperfusion in the presence of exogenously added ATP (10 mu M) plus ARL caused an additional reduction of both aforementioned effects. In contrast, elevation of ATP degradation by apyrase (I U/ml), a soluble ectonucleotidase, or addition of adenosine (10 mu M) provoked an increase in gap formation during reperfusion that could be completely inhibited by 8-phenyltheophylline (8-PT; 10 PM), an adenosine receptor antagonist. In Langendorff-perfused rat hearts, the reperfusion-induced increase in water content was significantly reduced by ARL plus ATP. Under conditions favouring ATP degradation, an increase in myocardial edema was observed that could be blocked by 8-PT. Conclusion: ATP, either released from cells or exogenously applied, protects against reperfusion-induced failure of the coronary endothelial barrier. Inhibition of ATP degradation enhances the stabilizing effect of ATP on barrier function. (c) 2006 European Society of Cardiology. Published by Elsevier B.V. All rights reserved.