MODIFICATIONS OF ANTIOXIDANT CAPACITY AND HEART ELECTRICAL-ACTIVITY INDUCED BY HYDROPEROXIDE IN NORMAL AND VITAMIN-E-FED RATS

Wistar rats, fed control or vitamin E-supplemented diet, were subjecte d to oxidative stress by a ten day treatment with daily intraperitonea l dose of tert-butyl hydroperoxide (TBHP) (0.1 mu mol/100 g body weigh t). The effectiveness of both diet and hydroperoxide treatment was est ablished by determining the antioxidant capacity of blood, liver, and heart with an enhanced luminescence method. While the diet addition of vitamin E increased the antioxidant capacity of all the tissues in tr eated and untreated animals the hydroperoxide treatment failed to decr ease liver antioxidant capacity in control dieted animals. The effect of the reiterated production of free radicals on electrophysiological properties of myocardium was determined by studying the heart rate in vivo and the time course of the surface electrical activity in papilla ry muscle fibers in vitro. In vivo, a significant tachycardia was foun d only in TBHP-treated; normal diet fed rats. The duration of action p otential, recorded in Krebs' solution at 26 degrees C, was not affecte d by diet in untreated animals but was modified by hydroperoxide treat ment in a diet-dependent way: shortened in normal diet-fed rats and le ngthened in vitamin E-supplemented diet-fed rats. On the basis of anal ogies with the results of electrophysiological recordings on different preparations subjected to oxidative stress in vitro, we suggest that the changes of action potential duration might depend on relative leve ls of added pro-oxidant and cell antioxidants.