We have studied the synergistic effects of squalene and polyunsaturated fatty acids (PUFA concentrate) on isoprenaline-induced infarction in rats with respect to changes in the levels of plasma diagnostic marker enzymes and myocardial antioxidant defense system. Intraperitoneal injection of isoprenaline caused a significant elevation in the levels of diagnostic marker enzymes; alanine aminotranferase (ALT), aspartate aminotransferase (AST), lactate dehydrogenase (LDH) and creatine phosphokinase (CPK) in plasma of experimental rats. There was a significant rise in the level of lipid peroxidation with concomitant decline in the level of reduced glutathione (GSH) and in the activities of glutathione-dependent antioxidant enzymes; glutathione peroxidase (GPX) and glutathione-Stransferase (GST), and antiperoxidative enzymes; superoxide dismutase (SOD) and catalase (CAT) in heart tissue. Combined supplementation of squalene and PUFA concentrate significantly prevented the isoprenaline-induced elevations in the levels of diagnostic marker enzymes in plasma of experimental groups of rats. A tendency to counteract the isoprenaline induced lipid peroxidation was also noticed. Their combined administration maintained the level of GSH and the activities of glutathione-dependent antioxidant enzymes and antiperoxidative enzymes at near normalcy. The results of the present study indicated that the combined administration of squalene and PUFA concentrate exerted significantly better cardio-protection against isoprenaline-intoxication as compared to that of per second supplementation. © 2007 Academic Journals. © 2008 Elsevier B.V., All rights reserved.