Catecholamine-induced free radicals in myocardial cell necrosis on experimental stress in pigs

Normal pigs, crossbreeds of Swedish Landrace and Yorkshire, about 6 months old, were subjected to experimental stress, induced by the myorelaxant succinylcholine, for 12 min. Besides one group of control pigs, one group of pigs were pretreated with alpha-tocopherol (vitamin E) combined with selenium (Tokosel Vet) injected i.m. every second day for 11 days, and another group was given zinc (ZnSO4.7H2O) in the fodder for 1 month plus one injection i.p. 2 days before the stress. The stress-induced heart lesions, morphologically graded according to evaluation scores, were significantly reduced in both the pretreated groups when compared with the control pigs. The blood levels of catecholamines (CA) were increased to about the same degree in the three groups during the stress. The protection observed is suggested to be due to the fact that vitamin E, selenium and zinc are involved in systems acting as scavengers of free radicals. The present results together with earlier ones are discussed to support the CA-hypothesis for stress-induced heart lesions: some types of stress can increase the sympathetic activity to such an extent that released CA, via beta-adrenoceptor mechanisms affects the cell metabolism to such a degree that cytotoxic free radicals are formed, producing myocardial cell necrosis.