Metabolical effects of Folidol 600 on the neotropical freshwater fish matrinxã, Brycon cephalus

The neotropical freshwater fish matrinxã, Brycon cephalus (Günther, 1869), was exposed to 1/3 of 96h-LC50 of Folidol 600 (methyl parathion) for 96 h and allowed to recover for 24, 48, 96, and 192 h. Acetylcholinesterase (AChE), alanine aminotransferase (ALAT), aspartate aminotransferase (AAT), lactate dehydrogenase (LDH), malate dehydrogenase (MDH), and glutamate dehydrogenase (GDH) were assayed in brain, liver, muscle, and plasma. Plasma and brain AChE activities were strongly inhibited (64% and 87%, respectively), remaining low in the brain during recovery. Liver ALAT decreased 59.4% and plasma ALAT increased 94.2%. This response, associated with GDH reduction during the recovery period, was attributed to impairment of amino acid metabolism and to liver damage. The increase of heart and plasma AAT suggested tissue injury. Liver and plasma LDH and MDH did not change during the exposure to Folidol, but liver MDH decreased 34% during recovery, indicating a failure of oxidative metabolism in such tissue. Hepatic glycogen and glucose levels decreased 80.4 and 55%, respectively, followed by glucose mobilization to the plasma. The hepatic and muscular profile of lactate after recovery suggested gluconeogenesis without tissue hypoxia. These results revealed that methyl parathion affects the intermediary metabolism of matrinxã and that the assayed enzymes can work as good biomarkers of organophosphorus pesticide contamination.