EFFECTS OF ENDOSULFAN ON BIOENERGETIC PROPERTIES OF LIVER-MITOCHONDRIA FROM THE FRESH-WATER CATFISH CLARIAS-BATRACHUS

The effects of a sublethal concentration of an organochlorine pesticide endosulfan on fish liver mitochondrial oxidation of isocitrate and succinate in vivo and in vitro were investigated. Endosulfan depressed the phosphorylation efficiency of mitochondria as inferred from a decrease in RCR and ADP/O ratio with isocitrate; whereas endosulfan at this concentration reduced State 3 rates and RCR with succinate. The CCCP-uncoupled rates and State 4 rates of oxidation with succinate were unaffected. However, endosulfan-treated mitochondria exhibited a low rate of oligomycin-inhibited ADP dependent CCCP stimulation during the oxidation of succinate. The activity of the masked and activated ATPase was significantly increased in the presence of endosulfan. There was also a progressive stimulatory effect of endosulfan on mitochondrial ATPase activity. These results demonstrate that endosulfan exerts an inhibitory effect on electron transport and acts directly on ATP synthetase complex which leads to an impairment in mitochondrial bioenergetics Of the fish. (C) 1994 Academic Press, Inc.