title: A comparative study on the relationship between acetylcholinesterase activity and acute toxicity in Daphnia magna exposed to anticholinesterase insecticides.
abstract: Acetylcholinesterase (AChE) activity was measured in Daphnia magna that had been exposed to four organophosphates (OPs; parathion, chlorpyrifos, malathion, and acephate) and one carbamate (propoxur) for 48 h. These results were related to acute toxicity (median effective concentration [EC50] for immobility). For the four OPs, the EC50s were 7.03 pM, 3.17 pM, 10.56 pM, and 309.82 microM, respectively. The EC50 for propoxur was 449.90 pM. Reduction in AChE activity was directly related to an increase in immobility in all chemicals tested. However, the ratio between the EC50 and the AChE median inhibiting concentration ranged from 0.31 to 0.90. A 50% reduction in AChE activity generally was associated with detrimental effects on mobility. However, for acephate, high levels of AChE inhibition (70%) were observed in very low concentrations and were not associated with immobility. In addition, increasing the concentration of acephate further had a slight negative effect on AChE activity but a strong detrimental effect on mobility. Binding sites other than AChE possibly are involved in acephate toxicity to D. magna. Our findings demonstrate different associations between AChE inhibition and toxicity when different chemicals are compared. Therefore, the value of using AChE activity as a biomarker in D. magna will be dependent on the chemical tested.
authors.affiliation: Division of Zoology, School of Animal and Microbial Sciences, University of Reading, Whiteknights, P.O. Box 228, Reading, Berkshire RG6 6AJ, United Kingdom.
authors.forename: Liane Biehl
authors.initials: LB
authors.lastname: Printes
authors.forename: Amanda
authors.initials: A
authors.lastname: Callaghan
mesh_terms: D000110:Acetylcholinesterase / Q000187:drug effects / Q000378:metabolism*; D000818:Animals; D004390:Chlorpyrifos / Q000633:toxicity; D002800:Cholinesterase Inhibitors / Q000737:chemistry / Q000633:toxicity*; D003621:Daphnia / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D007306:Insecticides / Q000633:toxicity*; D007928:Lethal Dose 50; D008294:Malathion / Q000633:toxicity; D009946:Organothiophosphorus Compounds / Q000633:toxicity; D010278:Parathion / Q000633:toxicity; D063088:Phosphoramides; D001074:Propoxur / Q000633:toxicity; D023382:Toxicity Tests, Acute
chemical_list: D002800:Cholinesterase Inhibitors; D007306:Insecticides; D009946:Organothiophosphorus Compounds; D063088:Phosphoramides; C001969:acephate; D010278:Parathion; D001074:Propoxur; D000110:Acetylcholinesterase; D004390:Chlorpyrifos; D008294:Malathion