In Vivo Effects of Deltamethrin Exposure on Activity and Distribution of Molecular Forms of Carp AChE

The in vivo effects of the insecticide deltamethrin (DM) on the activity and molecular forms of acetylcholinesterase (AChE, EC 3.1.1.7) were examined in different organs (brain, blood serum, heart, liver, and skeletal muscle) of carp. The chosen exposure conditions were a DM concentration of 2 μg/liter in the water (12 ± 1°C) for 3 days. All the treated fish survived the experiment, though the effects of the treatment were very visible: the fish always turned on their side, and the skin/scales became infected during the exposure to DM. DM did not result in a significant change in the AChE activity in any of the studied organs except the blood plasma, where the exposure resulted in an AChE activity decrease of as much as 20%. The ratio of membrane-bound to salt-soluble AChE forms was determined in the control fish. This ratio increased in the sequence heart, skeletal muscle, liver, and brain. The distribution of the AChE molecular forms was studied in the above tissues. The brain and liver contained forms G1, G4, and A12, the heart and skeletal muscle G4, A4, and A12, and the blood serum G1 and G4. The exposure to 2 μg/liter DM for 3 days caused hardly any changes in the pattern of the different AChE molecular forms. A small, but significant (P < 0.05) increase in the proportion of the G4 form was observed in the liver, while G1 and A12 decreased by a few percent (but insignificantly). No other tissues investigated exhibited any changes in the distribution of the AChE molecular forms. The DM accumulation in the various organs was likewise examined. The DM content was lower in all tissues than the limit of detection, which was 0.002 mg/1000 g wet tissue for the brain and heart and 0.0005 mg/1000 g wet tissue for the other organs (fat, guts, kidney, liver, roe, and skeletal muscle), due to the differences in the available quantities of the different organs. This study demonstrates that DM has an effect on the distribution of the AChE molecular forms, even if its activity itself is not disturbed. However, this phenomenon is not manifested strongly at this present relatively low water temperature.