Effect of Methyl Parathion on the Carbohydrate Metabolism of the Fish, Cirrhinus Mrigala

In general, any stress inducing substance will affect the respiratory metabolism of an animal. Any alteration in the intermediary metabolism due to stress is bound to affect the activity of oxidative enzymes like lactic dehydrogenase (LDH) and succinic dehydrogenase (SDH). Both enzymes are involved in carbohydrate metabolism and have been used as an indicative criterion of exposure to chemical stress. Several authors have reported that the disturbance in the oxidative metabolism which leads to an alteration in whole oxygen consumption in different species of fishes exposed to pesticides. Carbohydrates are the primary and immediate source of energy. In stressed condition, the carbohydrate reserve (glycogen) is depleted to meet the energy demand. Depletion of glycogen may be due to the direct utilization for energy generation, a demand caused by the pesticide induced hypoxia. Similar findings have been reported in frog Rana tigrina. Glycogenolysis seems to be the result of increased secretion of catecholamines due to stress. Pesticides also inhibit energy production by suppressing aerobic oxidation of carbohydrates leading to energy crisis in animals. LDH and SDH are widely used in toxicology and clinical chemistry to diagnose the cell, tissue and organ damage. In the present study, the toxicological effect of methyl parathion on the LDH and SDH activity has been made in the fish, Cirrihinus mrigala. The study revealed that the acute toxicity (TUa) of methyl parathion was 14 ppm.