The cardioprotective effects of ischemic 'preconditioning' are not mediated by adenosine receptors in rat hearts

BACKGROUNDAdenosine receptor activation has been proposed to explain the cardioprotective effect of ischemic preconditioning in rabbit hearts. We tested this hypothesis in a rat model by assessing whether administration of an adenosine antagonist could block the protective effect of preconditioning and whether adenosine is able to reduce infarct size in rat hearts when given before sustained coronary occlusion.METHODS AND RESULTSWe assessed the effects of the adenosine antagonist 8-(p-sulfophenyl)theophylline (SPT) and adenosine on myocardial infarct size and the incidence of ventricular arrhythmias in five groups of rats: control (nonpreconditioned)+vehicle, control+SPT, preconditioned+vehicle, preconditioned+SPT, and control (nonpreconditioned)+adenosine. All rats underwent 90 minutes of coronary artery occlusion followed by 4 hours of reperfusion while preconditioned rats underwent three 3-minute episodes of ischemia, each separated by 5 minutes of reperfusion before sustained occlusion. The area at ri...