Endosulfan effects on muscle malate dehydrogenase of the freshwater catfish Clarias batrachus

• Published in: Ecotoxicology and environmental safety Vol. 56; no. 3; pp. 425 - 433
• Main Authors: Mishra, Rajnikant, Shukla, S.P.
• Format: Journal Article
• Language: English
• Published: San Diego, CA Elsevier Inc 01.11.2003; Elsevier
• Subjects: Agnatha. Pisces; Animal, plant and microbial ecology; Animals; Applied ecology; Biological and medical sciences; Catfish; Catfishes - physiology; Clarias batrachus; Ecotoxicology, biological effects of pollution; Effects of pollution and side effects of pesticides on protozoa and invertebrates; Effects of pollution and side effects of pesticides on vertebrates; Endosulfan; Endosulfan - toxicity; Enzyme purification; Freshwater; Fundamental and applied biological sciences. Psychology; Hydrocarbons, Chlorinated; Insecticides - toxicity; Malate dehydrogenase; Malate Dehydrogenase - drug effects; Malate Dehydrogenase - pharmacology; Mitochondria; Muscle; Muscle, Skeletal - enzymology; Endosulfan; Malate dehydrogenase; Muscle; Catfish; Enzyme purification; Insecticide; Purification; Enzyme; Toxicity; Pesticides; Enzyme inhibitor; Clarias batrachus; Clariidae; Freshwater environment; Vertebrata; Organochlorine compounds; Pisces; Water pollution; Oxidoreductases
• ISSN: 0147-6513; 1090-2414
• DOI: 10.1016/S0147-6513(03)00006-X

The effects of a sublethal concentration of an organochlorine pesticide endosulfan were investigated on crude and purified forms of cytoplasmic malate dehydrogenase (cMDH) and mitochondrial malate dehydrogenase (mMDH) in the muscle of the freshwater catfish Clarias batrachus. Endosulfan treatment reduced significantly the activity and the specific activity of cMDH and mMDH but had no effect on total cytoplasmic and mitochondrial protein contents. This indicates a decline in the efficiency of aerobic energy metabolism in endosulfan-treated fish. The polyacrylamide gel electrophoresis showed two distinct isoforms (C1 and C2) of cMDH and only one form of mMDH. The inhibition produced by endosulfan in vivo was of mixed noncompetitive/uncompetitive type for crude as well as purified cMDH and mMDH. However, in vitro inhibition was of simple noncompetitive and mixed competitive/noncompetitive type for purified cMDH and mMDH, respectively. Citrate was found to be an uncompetitive inhibitor of cMDH and mixed noncompetitive/uncompetitve inhibitor of mMDH. The inhibitory patterns were modulated by endosulfan. These results demonstrate inhibitory effects of endosulfan on skeletal muscle MDH of the freshwater catfish Clarias batrachus and inhibition effects are mediated through enzyme/substrate/endosulfan complexing.