ABSTRACT
The antioxidant effect of dl-alpha-tochopherol acetate [vitamin E], ascorbic acid [Vitamin C] and reduced glutathione [GSH] were studied in-vivo and in vitro peroxidizing system of fish hepatic microsomes. Lipid peroxidation [LP] measured as malondialdehyde [MDA] compound, was not significant altered and inhibited until the concentrations of these antioxidant reached a critical level which depend on the effectiveness of the oxidative stress. Combination between these antioxidants [dl-alpha-tochopherol and GSH] or [dl-alpha-tochopherol and ascorbic acid] are elicit a marked and ascorbic acid] are elicit a marked and progressive reduction to lipid peroxidation. The rational of the cooperation was discussed on the basis of the hydroperoxyl radical scavenging capacity of vitamin E and the reduction of membrane hydroperoxide by glutathione and ascorbic acid. The inhibition of LP by dl-alpha-tochopherol acetate and glutathione was found concomitantly with a decrease in the concentration of its reduced form and a corresponding increase in oxidized tochopherol and glutathione disulfide levels. The study also investigated the relationship between LP and some enzyme inactivation in fish hepatic microsomes. In microsomes incubated with iron as [ferric chloride], glucose-6-phosphatase [G6P-ase] and cytochrome P-450 [Cyt. P-450] levels were decreased rapidly and concurrently with increased level of thiobarbituric acid-reactive substances. Microsomal nicotinamide adenine dinucleotide phosphate cytochrome-c reductase [Cyt-cRas] little affected during incubation period. Addition of antioxidant partially protected against inactivation of G6P'ase and Cyt P-450, as well as LP induced by ferric chloride