The possible role of adrenergic component in ischemic preconditioning.

The role of adrenergic mechanism in the cardioprotective effect of ischemic preconditioning against ischemia-reperfusion induced injury in in vivo dog heart and isolated rat heart was investigated. Anesthetized dogs were subjected to LAD coronary artery ligation for 60 min followed by reperfusion for 4 h. Preconditioning protocol was 5 min of ischemia followed by reperfusion for 10 min. Rat hearts were subjected to global ischemia for 30 min followed by reperfusion for 30 min. Preconditioning protocol was 5 min global ischemia followed by reperfusion for 5 min repeated four times. Infarct size, electrocardiographic changes and release of LDH were estimated to assess the extent of cardiac injury. Preconditioning reduced the infarct size, ST segment elevation and prevented the loss of R wave. Prazosin attenuated the cardioprotective effect of preconditioning in dog. Preconditioning conferred protection against ischemia-reperfusion induced cardiac injury and reperfusion-induced arrhythmias in isolated rat heart. Reserpine pretreatment attenuated this protective effect of preconditioning on reperfusion-induced arrhythmias. These observations suggest the involvement of adrenergic mechanism in the cardioprotective and antiarrhythmic effect of ischemic preconditioning in dog and rat species respectively.