Ischemic Preconditioning and Metabolism of Myocardial Adrenaline

We implanted under urethane narcosis microdialysis probes into myocardium of Wistar rats. In experimental group we used ischemic preconditioning. After this left descending coronary artery was occluded for 60 minutes and then reperfused for 60 min. In control group prolonged occlusion was preceded by 30 min of rest. Significant elevation of noradrenaline concentration in myocardial interstitium was noted at 20(th) and 10(th) minutes of testing ischemia in experimental and control groups respectively. From 20(th) minute to the termination of occlusion noradrenaline concentration in myocardial in animals of control group was significantly higher than that in preconditioned animals. Concentration of dihydroxyphenylglycol in interstitium reflecting noradrenaline metabolism in axoplasm fell during ischemia and rose when reperfusion was started. Elevation of dihydroxyphenylglycol was statistically significant compared with both baseline level and control (p<0.005) practically at all stages of reperfusion. Thus ischemic preconditioning inhibits effectively noradrenaline accumulation in myocardial interstitium during prolonged ischemia. After ischemic preconditioning normal mechanism of noradrenaline reuptake functions longer however because of impaired storage in vesicles substantial part of noradrenaline remains in free state in axoplasm to be subjected to deamination with participation of monoamine oxidase.