Comparison of Ventricular Cell Action Potentials of Combined Irradiation-burn Injury with that of Radiationor Burn Injury / 第三军医大学学报

ABSTRACT

Fifty-seven rats were randomly divided into 6 groups. The ventricular cell action potentials of combined irradiation-burn injury in situ were compared with that of radiation or burn injury and the recovery process from the effect of combined injury on myocardium was observed by floating microelectrode. The results obtained were as follows.Similar to that of radiation or burn injury, both the depolarization and repo-larization of action potential were also changed by combined radiation-burn injury significantly, but there are some peculiar characteristics of its own. Twenty-four hours after combined injury, the amplitude of action potential (APA, -13.6%), maximum depolarization rate, (Vmax, -41.2%) , as compared with that of cort-rol. The changes of heart rate were different. In burn group.it increased by+9.8%; in radiation group, it decreased by -17.4%, however, it appoximated to control level in combined group at 24 hours after injury. Three days after combined injury, the HR was decreased by -12%, after 5 days, it only recovered slightly. Combined injury decreased the mean repolarization rate(MRR, -26.3%--13.2%)and prolonged the duration of action potential (APD), especially APD50 and APD90,( +33.7%-+ 22.9%) and( + 6.9%- + 18%)respectively.These results suggest that the effects of combined injury are not a simple algebraic sum of radiation and burn injury. In some aspects, such as Vmax, there is synergism between the effects of radiation and burn injury, but in other cases, e.g., HR, these effects seem to be counterblanced each other. These changes in ventricular action potentials of the combined radiation-burn injury are also a reversible process. In general, the earlier the response of injury (such as in APA and Vmax) appears, the faster the recovery occurs and vice versa (such as in Vmax and HR) .