Inhibitors of the MPTP protect the adult heart against ischaemia and reperfusion injury with or without cardioplegic arrest. Opening of the MPTP is a critical event in some forms of myocardial necrotic and apoptotic cell death.We have recently shown that inhibition of the MPTP also protects the immature heart against ischaemia and reperfusion injury (Khan et al J Physiol 567P PC21, 2005). In this study we investigated the effect of MPTP inhibitors 0.2mM Cyclosporin A (CsA) and 1.0mM Sanglifehrin A (SfA), when used as an adjunct to cardioplegia. Functional activity was assessed in immature (14 days old) rat hearts that were perfused in the Langendorff mode, subjected to cardioplegic normothermic ischaemic arrest for 90 minutes with or without MPTP inhibitors, and followed by 50 minutes reperfusion. The time to ischaemic contracture was not affected by the drugs nor was the percentage recovery in rate pressure product affected compared to control hearts receiving cardioplegia alone. In contrast to adult hearts, MPTP inhibitors do not confer additional protection when added to cardioplegia in the immature heart. This suggests physiological and metabolic differences between the MPTP of adult and immature hearts.

Supported by the British Heart Foundation