Nemcsok_1990_Pestic.Biochem.Physiol_37_140

The effects of the insecticide methidathion (MD) (S-2,3-dihydro-5-methoxy-2-oxo-1,3,4-thiodiazol-3-yl-methyl-O,O-dimethyl-phosphodithioate) were studied on the molecular forms of acetylcholinesterase (AChE, EC 3.1.1.7) in the brain and liver in carp. Both organs contain three different molecular forms: G1, G4, and A12. During exposure of fish to 2 ppm MD in vivo, the enzyme activity decreased significantly in the tissues investigated. Moreover, the relative distribution of the AChE molecular forms changed compared to that in the control animals. There was a significant decrease in the G1 form and an increase in the G4 form in the brain, while in the liver there was a decrease in the G4 form and an increase of about 50% in the G1 form. The results suggest that the investigation of fish AChE molecular forms could contribute to an understanding of fish AChE at a molecular level and emphasize the importance of in vivo and in vitro approaches in assessing chemical effects and their potential hazards in the aquatic environment.