Hyperkalaemic cardioplegic arrest and ischaemic preconditioning are two established techniques known to protect the heart against ischaemia and reperfusion injury. Inhibition of mitochondrial permeability transition pore has also been shown to be cardioprotective. The extent of the release of NAD+ during reperfusion has been used as a measure of mitochondrial pore opening. In this study we compared recovery and NAD+ release (measured using HPLC) from isolated Langendorff guinea-pig hearts following 30 minutes global ischemia with or without protection with either hyperkalemia (buffer containing 20mM K+)or two cycles (2+3 min) of ischaemic preconditioning.

Both treatments resulted in significant functional recovery (recovery in left ventricular developed pressure was 61±3% for control compared to 84±3 and 82±3% for hyperkalaemia and preconditioning, respectively). However, only hyperkalaemia was associated with marked and significant reduction in NAD+ loss upon reperfusion. This work shows that in guinea-pig isolated perfused hearts, hyperkalaemia but not ischaemic preconditioning is associated with inhibition of mitochondrial pore opening during reperfusion.