Differential effects of α- and γ-tocopherol on low-density lipoprotein oxidation, superoxide activity, platelet aggregation and arterial thrombogenesis

OBJECTIVES This study was designed to examine the differential effects of α- and γ-tocopherol on parameters of oxidation-antioxidation and thrombogenesis. BACKGROUND Experimental studies have shown that antioxidants, such as vitamin E (α-tocopherol), improve atherosclerotic plaque stability and vasomotor function, and decrease platelet aggregation and tendency to thrombus formation. METHODS Sprague Dawley rats were fed chow mixed with α- or γ-tocopherol (100 mg/kg/day) for 10 days. filter soaked in 29% FeCl3 was applied around the abdominal aort to study the patterns of arterial thrombosis. The aortic blood flow was observed and continuously recorded using an ultrasonic Doppler flow probe. ADP-induced platelet aggregation, low-density lipoprotein oxidation induced by phorbol 12-myristate 13-acetate (PMA)-stimulated leukocytes, superoxide anion generation and superoxide dismutase (SOD) activity were also measured. RESULTS Both α- and γ-tocopherol decreased platelet aggregation and delayed time to occlusive thrombus (all p < 0.05 vs. control). Both α- and γ-tocopherol decreased arterial superoxide anion generation, lipid peroxidation and LDL oxidation (all p < 0.05 vs. control), and increased endogenous SOD activity (p < 0.05). The effects of γ-tocopherol were more potent than those of α-tocopherol (p < 0.05). CONCLUSIONS This study indicates that both α- and γ-tocopherol decrease platelet aggregation and delay intraarterial thrombus formation, perhaps by an increase in endogenous antioxidant activity. γ-Tocopherol is significantly more potent than α-tocopherol in these effects.