Metabolic changes in the snake head fish Channa punctatus chronically exposed to endosulfan

Abstract

The chronic toxic effects of a commonly used pesticide endosulfan on the carbohydrate metabolism of the fresh water telcost fish Channa punctatus were investigated. The fish were exposed to a sub-lethal concentration (0.2 μg l−1) for 15, 30, and 60 days. The levels of glucose, total plasma proteins, lactic acid and haemoglobin in the blood, glycogen and lactic acid contents of liver and muscles were also measured. Alterations in the activities of hexokinase, lactate dehydrogenase and pyruvate dehydrogenase in the glycolytic pathway, and succinate dehydrogenase in the citric acid cycle were examined in the liver, kidney, intestine, brain, gills and muscles. The results showed that 30 and 60 days of exposure produced more significant changes in different parameters in comparison to 15 days. There was a decrease in blood glucose and total plasma proteins but lactic acid and haemoglobin levels were higher in endosulfan exposed fish than in control fish. Glycogen and lactic acid contents of the liver and muscles were depleted. The activity of hexokinase in liver, kidney and intestine was inhibited after 60 days of exposure but in muscles the enzyme activity was elevated. Glucose-6-phosphatasc was inhibited in all the tissues. Lactate dehydrogenase, pyruvate dehydrogenase and succinate dehydrogenase activities decreased in the liver, kidney, brain and gills after 30 and 60 days of exposure. In the muscles, the activities of lactate dehydrogenase and pyruvate dehydrogenase were elevated while succinate dehydrogenase was inhibited. The study showed that formation of glycogen and its breakdown were impaired in the liver. In the muscles, the rate of glycolysis increased probably due to pesticide induced muscular excitment.