Cardiac bioenergetics as biomarkers for insecticides toxicity .2. In vivo effects of chlordecone on adenine nucleotide pool metabolism and cyclic-AMP levels in rat myocardium, liver, kidney, brain and skeletal muscle
Background: Chlordecone (kepone(11)), 1, 1a, 3, 3a, 5, 5a, 5, 5b, 6-deca chlorooctahydro 1, 3, 4-metheno-2H-cyclobutal (Cd)-pentalen-2-one, is an organochlorine insecticide which was extensively used to control fire ants in the southern regions of the United State. Accidental exposure to chlordecone resulted in severe tremors, incoordination, blurring vision and ataxia in humans. Despite of several reports, the mechanisms of toxic action of chlordecone has not elucidated. Chlordecone has been shown to be a potent inhibitor of several ATP-dependent reactions. In the preceding study, we found that chlordecone is a potent inhibitor of mitochondrial ATPase activity and the inhibition site was identified as the oligomycin-sensitivity conferring protein (OSCP).
Rationale: We tested whether administration of chlordecone affects tissue bioenergetics, i.e., ATP pool metabolism, by either inhibiting mitochondrial ATPase when catalyzes ATP synthesis or catalyses ATP hydrolysis or both, in vivo.
Methods: Rats received a single oral does of chlordecone (200 mg/kg in corn oil) by intubated lavage. Early signs of intoxication were recorded. After 6 hours, animals were decapitated and different tissues were quickly dissected and frozen in liquid nitrogen. Tissue samples were extracted and analyzed by the HPLC to measure ATP, ADP, AMP, adenosine, inosine, hypoxanthine, xanthine, cAMP and NAD(+) levels.
Results: Early signs of chlordecone-induced neurotoxicity were evident 2 hours following oral administration and characterized by severe and prolonged tremors upon anxiety or stimulation and muscular spasticity. In a preliminary study, a single oral dose of chlordecone (200 mg/kg) caused a 100% mortality after 24 hours of administration (n = 16). Despite of severe signs of chlordecone-induced neurotoxicity, none of the animals have died 6 hours after administration. Chlordecone induced significant loss of tissue ATP levels in rat myocardium (p < 0.001, n = 9), brain (p < 0.01, n = 16), liver (p < 0.05, n = 10). and kidney (p < 0.001, n = 9) compared to the untreated control-group. ATP levels were not significantly reduced in skeletal muscle. ADP levels were significantly reduced in the liver (p < 0.5), kidney (p < 0.001) and the brain (p < 0.01) compared to the control group. A significant decline in the level of cAMP was observed mainly in the liver (p < 0.005 vs the control group). Chlordecone differentially reduced the total adenine nucleotide, nucleoside, purine, cAMP and NAD(+) pool compared to the control group.
Conclusion: Chlordecone significantly reduced the steady state levels of adenine nucleotide pool suggesting that it is not only inhibit ATP utilization but also impairs ATP synthesis. Results from this study document that variable tissue sensitivity to chlordecone poisoning. These tissue-related differences may be due to variable energy requirements and reserve in different tissues as well as the number, size and the efficiency of mitochondria to produce ATP.
