The role of adenosine in preconditioning by brief pressure overload in rats

Background/Purpose: Brief pressure overload of the left ventricle reduced myocardial infarct (MI) size in rabbits has been previously reported. Its effects in other species are not known. This study investigates effects of pressure overload and the role of adenosine in rats in this study. Methods: MI was induced by 40-minute occlusion of the left anterior descending coronary artery followed by 3-hour reperfusion. MI size was determined by triphenyl tetrazolium chloride staining. Brief pressure overload was induced by two 10-minute episodes of partial snaring of the ascending aorta. Systolic left ventricular pressure was raised 50% above the baseline value. Ischemic preconditioning was elicited by two 10-minute coronary artery occlusions. Results: The MI size (mean ± standard deviation), expressed as percentage of area at risk, was significantly reduced in the pressure overload group as well as in the ischemic preconditioning group (17.4 ± 3.0% and 18.2 ± 1.5% vs. 26.6 ± 2.4% in the control group, p <0.001). Pretreatment with 8-(p-sulfophenyl)-theophylline (SPT), an inhibitor of adenosine receptors, did not significantly limit the protection by pressure overload and ischemic preconditioning (18.3 ± 1.5% and 18.2 ± 2.0%, respectively, p <0.001). SPT itself did not affect the extent of infarct (25.4 ± 2.0%). The hemodynamics, area at risk and mortality were not significantly different among all groups of animals. Conclusion: Brief pressure overload of the left ventricle preconditioned rat myocardium against infarction. Because SPT did not significantly alter MI size reduction, our results did not support a role of adenosine in preconditioning by pressure overload in rats.