Esterase inhibition in tadpoles of Scinax fuscovarius (Anura, Hylidae) as a biomarker for exposure to organophosphate pesticides.
OBJECTIVE
Organophosphate pesticides (OPs) are among the most used insecticides in agriculture, causing the inhibition of esterases like acetylcholinesterase (AChE), butyrylcholinesterase (BChE) and carboxylesterase (CbE). Pesticides can reach the aquatic environment, posing risks to non-target organisms, including tadpoles.


METHODS
In this work, we characterized the activities of AChE, BChE and CbE in tadpoles of the snouted treefrog Scinax fuscovarius, and verified their in vitro sensibility to different inhibitors [phenylmethane sulfonyl fluoride (PMSF), tetra-isopropylpyrophosphamide (iso-OMPA) and the OP diazinon]. In vivo effects of diazinon and esterase recovery after 2-pyridine-aldoxime (2-PAM) treatment of the protein extract were also studied in tadpoles with distinct stages of development exposed to 1 and 3 mg/l for 2 and 7 days.


RESULTS
Optimal conditions were established for AChE and CbE; BChE activity was negligible. PMSF affected esterase activities and is not recommended for homogenization buffers. Iso-OMPA treatment caused no changes in AChE and CbE activities, but diazinon inhibited these enzymes in a dose-responsive manner. In vivo, CbE activity was insensitive to diazinon in younger tadpoles, but inhibited after 2 days of exposure in more developed tadpoles. AChE activity was inhibited after 2 and 7 days of exposure, in a dose-responsive manner. Esterase reactivation by 2-PAM was obtained both in vitro and in vivo.


CONCLUSIONS
(1) Tadpoles can be adequate sentinel organisms in biomonitoring studies of OP contamination; (2) AChE was more sensitive than CbE to diazinon; (3) tadpoles from earlier developmental stages seems to be less responsive to OPs; (4) AChE activity was sensitive to diazinon in both development stages, being a better OP biomarker.
Leite
Patricia Zazeri
PZ
Departamento de Química e Ciências Ambientais, Instituto de Biociências, Letras e Ciências Exatas, Universidade Estadual Paulista, Rua Cristóvão Colombo 2265, CEP 15054-000, São José do Rio Preto, Brazil.
Margarido
Tatiana Cristina Stefani
TC
de Lima
Daína
D
Rossa-Feres
Denise de Cerqueira
Dde C
de Almeida
Eduardo Alves
EA
D000110:Acetylcholinesterase / Q000187:drug effects; D000818:Animals; D001001:Anura / Q000254:growth & development / Q000378:metabolism*; D015415:Biomarkers / Q000378:metabolism; D002091:Butyrylcholinesterase / Q000187:drug effects; D043182:Carboxylesterase / Q000037:antagonists & inhibitors; D003976:Diazinon / Q000633:toxicity; D004791:Enzyme Inhibitors / Q000633:toxicity*; D004950:Esterases / Q000037:antagonists & inhibitors*; D007814:Larva / Q000187:drug effects / Q000201:enzymology; D010755:Organophosphates / Q000633:toxicity*; D010575:Pesticides / Q000633:toxicity*; D013770:Tetraisopropylpyrophosphamide / Q000633:toxicity; D014105:Tosyl Compounds / Q000633:toxicity; D014874:Water Pollutants, Chemical / Q000633:toxicity*
D015415:Biomarkers; D004791:Enzyme Inhibitors; D010755:Organophosphates; D010575:Pesticides; D014105:Tosyl Compounds; D014874:Water Pollutants, Chemical; C003614:4-toluenesulfonyl fluoride; D013770:Tetraisopropylpyrophosphamide; D004950:Esterases; D043182:Carboxylesterase; D000110:Acetylcholinesterase; D002091:Butyrylcholinesterase; D003976:Diazinon
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