ASSOCIATION OF PRE-ISCHAEMIC DISTURBANCES IN ENERGY METABOLISM WITH POSTISCHAEMIC DYSFUNCTION OF THE RAT ISOLATED WORKING HEART

1. Metabolic and functional effects of two protocols of preconditioning were compared in rat isolated hearts subjected to 20 min global ischaemia (37°C) and reperfusion (30 min Langendorff + 15 min working). Prior to the ischaemic period, hearts were perfused according to Langendorff (control group) or were preconditioned by three 5 min cycles or two 10 min cycles of ischaemia and reperfusion (PC-I and PC-II groups, respectively). 2. There was no difference in the contractile function between the two preconditioned groups at the onset of sustained ischaemia, although the PC-II group showed enhanced release of adenosine (Ado), inosine, hypoxanthine and xanthine into the interstitium accompanied by losses of tissue adenine nucleotides (ΣAN = ATP + ADP + AMP), total creatine (ΣCr = phosphocreatine + creatine) and activation of glycolysis following the preconditioning period. During reperfusion, the PC-I group showed enhanced functional recovery, higher contents of ΣAN and ΣCr, and the smallest lactate dehydrogenase release compared with these indices in the control and PC-II groups. Postischaemic myocardial dysfunction was similar in the control and PC-II groups. 3. Functional recovery of hearts in both preconditioned groups was positively correlated with myocardial contents of ATP, ΣAN and ΣCr at the end of reperfusion, but not with pre-ischaemic Ado release into the interstitium. The results suggest that pre-ischaemic disturbances of energy metabolism, rather than activation of Ado receptors or stunning, may contribute to efficacy of multiple preconditioning in the rat isolated heart.