Pesticides used in agricultural fields create a series of toxicological and environmental problems. Methyl parathion (MP)，an organophosphorus (OP) insecticide is a widelyused pesticide and is highly toxic to non-target organisms. Fish has been used as indicator speciesfor monitoring of pollution in the aquatic environment Mystus seenghala，an Indian major carp is an edible fish and is highly sensitive to slight stress. Recently, fish biomarkers are widely used to determine the internal and external health status caused by chemicals.
WhenM. seenghala were exposed to acute (0.09 ppm) and sub lethal (0.009 ppm) concentrations of MP to determine the alterations in antioxidant and metabolic enzyme activities in blood plasma. Intoxication with MP resulted in induction of oxidative stress which implies that fish utilizes enzymatic mechanisms to tolerate the effects caused by generated ROS due to MPaccumulation. Significant alterations in GOT and GPT activity in plasma during acute as well as sub lethal exposure might have resulted from the organ damage. Further, MP should be used with caution in order to protect natural waters and aquatic organisms