EFFECTS OF ENDOSULFAN ON BIOENERGETIC PROPERTIES OF SKELETAL-MUSCLE MITOCHONDRIA FROM THE FRESH-WATER CATFISH (CLARIAS-BATRACHUS)

The effects of a sublethal concentration of an organochlorine pesticid e endosulfan on fish skeletal muscle mitochondria oxidizing isocitrate and succinate in vivo and in vitro were investigated. The endosulfan depressed significantly State 3 rates and RCR with succinate, whereas it prevented completely the oxidation of isocitrate. The CCCP-uncouple d rates and State 4 rates of succinate oxidation remained unaffected b y endosulfan. The activity of masked ATPase was significantly increase d in presence of endosulfan. There was a progressive stimulatory effec t of endosulfan on mitochondrial ATPase. The skeletal muscle fibres of endosulfan exposed fish undergo ultrastructural changes that are char acterized by deformation of the myofibrils and disappearance of mitoch ondria. Summarizing, it can be stated that endosulfan exerts an inhibi tory effect on electron transport and affects ATP synthetase complex l eading to an impairment in mitochondrial bioenergetics, which can be c orrelated with marked ultrastructural alterations in the skeletal musc le fibres of the fish.