Preconditioning by brief ischaemic episodes in the isolated rat heart assessed by 31P NMR spectroscopy: dissociation between metabolic and functional recovery?

31P NMR spectroscopy was used to investigate whether improved functional recovery in ischaemic preconditioning was due to improved metabolic recovery in isolated rat hearts. The preconditioning stimulus was global ischaemia of 1 or 4 min followed by 12 min of reperfusion (Langendorff mode). The hearts were then subjected to a main ischaemic period of 16 min and 40 min of reperfusion. Functional and metabolic recoveries of hearts were compared to a control group subjected only to the main ischaemia. Preconditioning improved recovery of contractile function during the final reperfusion. Thus left ventricular developed pressure (LVDP) and heart rate (HR) product after 40 min of reperfusion recovered to 56, 67 and 68% in the control group, 1 min group and 4 min group, 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 values) at the end of the final reperfusion. We conclude that the improved functional recovery in preconditioning is not due to a higher level of high energy phosphates or less acidosis during the final reperfusion.