THE ANTIOXIDANT EFFECT OF SELENIUM ON MALATHION TOXICITY ON THE BRAIN OF MALE WISTAR RAT.
1.1. Background to the Study
The single-dose acute oral toxicity test is used in preliminary evaluation of virtually all substances of suspected biological activity. The test is based on administration of graded dosage of chemical in relation to body mass. Malathion is an organophosphate insecticide which is registered for agricultural uses and for landscape maintenance, vector control, and structural pest control (Cheeseman et al., 2004). This assessment of potential dietary exposures addresses the residues that may occur as a result of agricultural uses of malathion. Organophosphate compounds inhibit the activity of cholinesterase which is an enzyme present in several body tissues and essential for the normal function of nerves.
Selenium belongs to essential microelements. Being a constituent of one of the main antioxidant enzymes – glutathione peroxidase – it is considered to be an antioxidant (Cheeseman et al., 2004). Its possible application as a protective agent against toxic metals and compounds as well as against oxidative stress have already been studied and the outcomes have seemed to be encouraging (Brugh, 2008). Selenium alone or in combination with vitamin E has already been found to prevent oxidative stress in brain of animals exposed to cigarette smoke (Tiwaryand, 2005) chromium (Chowdhury et al., 2005) and mercury (Oser, 2005).
In living systems, oxidation is a basic part of the normal metabolic process, in which reactive oxygen species (hydrogen peroxide and hypochlorous acid) and many free radicals (hydroxyl radical (OH) and superoxide anion) are generated. Rapid production of free radicals may cause alteration in the structure and function of cell constituents and membranes and can results in human neurologic and other disorders such as cancer, diabetes, inflammatory disease, asthma, cardiovascular, neurodegenerative diseases, and premature aging. Therefore, the prevention of the above conditions requires the presence of antioxidants or the free radical scavenging molecules in the body.