Adenosine Contributes to Neutrophil-mediated Loss of Myocardial Function in Post-ischemic Guinea-pig Hearts

Tissue injury associated with myocardial ischemia is assumed to largely result from the toxic effects of active oxygen species generated by accumulated polymorphonuclear leukocytes (PMNs). Recent reports have indicated that adenosine can interfere with the PMN function in vitro. The potential of adenosine to influence PMN-mediated myocardial tissue injury was assessed using a model of ischemia-reperfusion injury developed in the isolated working guinea-pig heart perfused with homologous PMNs. After an initial work phase, hearts were subjected to 30 min low-flow ischemia (1 ml/min) in the absence and presence of PMNs. Work was resumed after 15 min reperfusion in a non-working mode (Langendorff). Adenosine in the coronary effluent reached a maximum of 0.2 μM during low-flow ischemia. Recoveries of external heart work and cardiac output were reduced from about 80% to about 40% by PMNs. Infusion of adenosine deaminase (ADA, 5 U/ml), theophylline (50 μM) or the selective A1-antagonist dipropyl-8-cyclopentylxanthine (0.1 μM) prevented this effect. Furthermore, application of adenosine (0.1 μM) in combination with PMNs also resulted in a loss of pump function, even in the absence of a direct ischemic stimulus. The data indicate that adenosine contributes to post-ischemic, PMN-mediated damage in the isolate working guinea-pig heart model by a receptor-mediated action.