PRECONDITIONING BY BRIEF ISCHEMIC EPISODES IN THE ISOLATED RAT-HEART ASSESSED BY P-31 NMR-SPECTROSCOPY - DISSOCIATION BETWEEN METABOLIC ANDFUNCTIONAL RECOVERY

P-31 NMR spectroscopy was used to investigate whether improved functio nal recovery in ischaemic preconditioning was due to improved metaboli c recovery in isolated rat hearts. The preconditioning stimulus was gl obal ischaemia of 1 or 4 min followed by 12 min of reperfusion (Langen dorff mode). The hearts were then subjected to a main ischaemic period of 16 min and 40 min of reperfusion. Functional and metabolic recover ies of hearts were compared to a control group subjected only to the m ain ischaemia. Preconditioning improved recovery of contractile functi on during the final reperfusion. Thus left ventricular developed press ure (LVDP) and heart rate (HR) product after 40 min of reperfusion rec overed to 56, 67 and 68% in the control group, 1 min group and 4 min g roup, respectively. However, the metabolic recovery was comparable in all groups. CrP and ATP recovered to levels of 67-78% (CrP) and 35-41% (ATP), and pH to a level of 7.13-7.15 (not different from baseline va lues) at the end of the final reperfusion. We conclude that the improv ed functional recovery in preconditioning is not due to a higher level of high energy phosphates or less acidosis during the final reperfusi on.