A comparative study of specific activities and in vitro inhibition of brain and serum acetylcholinesterase (AChE; EC 3.1.1.7) and serum butyrylcholinesterase (BChE; EC 3.1.1.8) by DDVP, an organophosphorus pesticide, was conducted in 11 freshwater teleost species belonging to four families (Cyprinidae: common carp Cyprinus cal;nio, bream Abramis brama, blue bream A. ballerus, white bream Blicca bjoerkna, roach Rutilus rutilus, bleak Alburnus alburnus, ide Leuciscus idus; Percidae: perch Perca fluviatilis, pikeperch Stizostedion lucioperca; Esocidae: pike Esox lucius and Coregonidae: whitefish Coregonus albula). Specific AChE and BChE activities in brain and serum of fish were determined. Brain AChE activity varied among fish species approximate to 10-fold, ranging from 192.6 to 1353.2 mu mol g(-1) h(-1): respectively in perch and whitefish. All cyprinids had higher brain AChE activity than those of other fish families. Serum AChE activity was 100-fold lower than in brain. Serum BChE activity was found only in cyprinids with the exception of the common carp. It varied from 163.8 to 970.3 mu mol g(-1) h(-1), respectively in roach and bleak. The bimolecular enzyme inhibition rate constants (k(II)s) and pI(50) values for DDVP were calculated. Sensitivity of fish AChEs both in brain and serum is similar to those of typical AChEs in mammals. The range of k(II)s was 3.4-51.7 x 10(3) mol(-1) 1 min(-1) (pI(50)s were 5.3-6.5), respectively in white bream and ide. In contrast, fish serum BChE was more sensitive to inhibition than typical BChE and AChE in mammals. Values of k(II) for BChE were 1.0-2.5 x 10(7) mol(-1) 1 min(-1) (pI(50) was 8.8-9.2), respectively in ide and bleak. (C) 2000 Elsevier Science Inc. All rights reserved.
