[Receptor and signalling mechanisms of antiarrhythmic effects of ischemic pre-conditioning]

It has been established that ischemic preconditioning (IP) exerts significant antiarrhythmic effects, as revealed in experiments both in vivo and in vitro. Consequently, processes arising within the myocardium play a key role in adaptive tolerance to ischemia/reperfusion. Preconditioning enhances cardiac electrical stability both in animals and humans. The antiarrhythmic effect of preconditioning is transient, with enhanced tolerance to ischemia-reperfusion triggered arrhythmogenesis dissipating 2-3 after the IP stimulus. The basis of the antiarrhythmic and cardioprotective effects of IP may differ. Preconditioning improves conduction of the cardiac electrical impulse, thereby preventing occurrence of re-entrant arrhythmias. NO-synthase and peroxynitrite play an important role in evolution of the antiarrhythmic effects of IP. Furthermore, intracellular Ca2+ may be a trigger of improved cardiac electrical stability after IP. It has been established that G(i/o)-protein coupled receptors are not involved in antiarrhythmic effects of IP, whereas bradykinin B2 and alpha1 adrenergic receptor activities are involved in IP-dependent improvements in cardiac electrical stability. Adenosine receptors contribute only partially to these effects. In terms of signalling mechanisms, protein kinase C appears essential to the antiarrhythmic effects of IP, whereas PI3-kinase and cyclooxygenase do not appear to be significantly involved. It has also been established that cardiac mast cells are involved in IP effects. Some data indicate that increased cardiac electrical stability with preconditioning depends upon mitoK(ATP) channel opening. Other data provide evidence that antiarrhythmic effects of preconditioning depends upon sarcK(ATP) channel opening. Some data indicate that an increase in electrical stability of heart after preconditioning depends upon mitoK(ATP) channel opening. Other data are evidence that antiarrhythmic effect of preconditioning depends upon sarCK(ATP) channel opening. Further work is needed to fully delineate the mechanistic basis of antiarrhythmic effects of IP.