EFFECT OF IMMOBILIZATION STRESS ON ANTIOXIDANT ENZYMATIC ACTIVITIES IN LIVER AND HEART; POSSIBLE MODIFICATION BY USING ANTIOXIDANT VITAMINS C AND E.
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As oxidative stress is a cellular and physiological condition of elevated concentration of reactive oxygen species (ROS), it causes molecular damage to vital structures and functions. Several factors can affect the antioxidants status or free radical generation such as air pollution, alcohol, cigarette smoke, non ionizing radiation and psychological stress. Oxidative stress is viewed as a continuous battle between inducers (pnooxidants) and a vast array of different protective factors (antioxidants). There is an expanding list of antioxidants, which can be divided into enzymatic such as superoxide dismutase (SOD) , catalase (CAT) and glutathione peroxidase (GSHPx) and non enzymatic such as vitamin C and vitamin E. Tissues have different oxidative loads and aggregated antioxidant capacity differs as a result The aim of this work is to study the changes which can happen in the lipid peroxidation and enzymatic antioxidant defense of liver and heart as a result of immobilization stress; possible modification by vitamin C and E supplementation. The present study was conducted on 40 male albino rats. They were divided into 4 groups; group(Thcontrol of 10 rats , group (2);stressed of 10 rats subjected to immobilization stress for 4 hours, 4 group (3) of 10 rats which received an oily solution of alpha tocopherol orally at a dose of 10mg/Kg body weight for 2 weeks prior to immobilization and group (4) of 10 rats which received 0.5 mg/Kg body weight of ascorbic acid for 2 weeks dissolved in the drinking water before immobilization. After the experimental period, all rats were anaesthetized by ether then sacrificed by decapitation, liver and heart were separated, weighed, homogenized and centrifuged. The supernatant was separated for estimation of SOD, GSHPx, catalase activity and lipid peroxides level. The present study showed that, restraint stress significantly reduced the activity of the liver and heart antioxidant enzymes. The impairment of antioxidant defensive mechanisms was associated with increased levels of peroxides indicating the toxic effects of the unantagonized free radicals formed during immobilization stress. Fortifring the endogenous antioxidant defense mechanisms with exogenously administered free radical scavengers, ascorbic acid and a-tocopherol (VII. E) significantly reduced liver and heart peroxides. Moreover, the antioxidant enzymes which were decreased during stress showed significant increase. Such change may be due to stimulation of their synthesis or reduction of their consumption. In conclusion, The present study showed that the enzymatic antioxidant defensive mechanisms of rat liver and heart were impaired during exposure to restraint stress. Oxygen free radicals are formed during stress; attack all membranes producing peroxidation of phospholipids followed by membrane damage , scavenging the free radicals by the exogenously administered scavengers (ascorbic acid) or (a -tocopherol) offered organs protection. This may open the way for trying a new strategy for treatment of heart and liver affection depcnding on combination of classic drugs with antioxidants to obtain full protection.