title: Carbofuran and malathion inhibit nucleotide hydrolysis in zebrafish (Danio rerio) brain membranes.
abstract: Carbofuran and malathion are broad spectrum pesticides widely used in agricultural practice throughout the world. Toxicity of these pesticides has been correlated with their inhibitory effects on acetylcholinesterase activity. Nucleotides are extracellular signaling molecules, which trigger multiple biological effects. Studies have demonstrated the co-transmission of acetylcholine and ATP at the nerve endings. The control of neurotransmitter ATP levels is promoted by enzymes named ectonucleotidases, which include nucleoside triphosphate diphosphohydrolase (NTPDase) family and ecto-5'-nucleotidase. Since acetylcholine and ATP are co-released at the synapse and the acetylcholinesterase inhibition is an important target for pesticide action, here we verified the effect of exposure in vitro and in vivo to carbofuran and malathion on ectonucleotidase activities from brain membranes of zebrafish. To verify if carbofuran and malathion have a direct inhibitory effect on NTPDase and 5'-nucleotidase activities in brain membranes of zebrafish, we have tested in vitro concentrations of pesticides varying from 0.25 to 5 mM. Carbofuran, in vitro, inhibited ATP and ADP hydrolysis in an uncompetitive manner, but no effect was observed on AMP hydrolysis. Malathion decreased ATP and ADP hydrolysis in competitive and an uncompetitive manner, respectively, but not altered AMP hydrolysis. After exposure to carbofuran (50 and 500 microg/L) during 7 days, ADP hydrolysis was significantly decreased in both concentrations tested (by 19 and 24.5%, respectively). Malathion, at 500 microg/L, was able to inhibit ADP and AMP hydrolysis (by 28 and 58.5%, respectively). This study has shown that ectonucleotidases from brain membranes of zebrafish can be a potential target for pesticide neurotoxicity.
authors.affiliation: Laboratório de Pesquisa Bioquímica, Departamento de Ciências Fisiológicas, Faculdade de Biociências, Pontifícia Universidade Católica do Rio Grande do Sul. Avenida Ipiranga, 6681, 90619-900 Porto Alegre, RS, Brazil.
authors.forename: Mario Roberto
authors.initials: MR
authors.lastname: Senger
authors.forename: Eduardo Pacheco
authors.initials: EP
authors.lastname: Rico
authors.forename: Marcelo
authors.initials: M
authors.lastname: de Bem Arizi
authors.forename: Denis Broock
authors.initials: DB
authors.lastname: Rosemberg
authors.forename: Renato Dutra
authors.initials: RD
authors.lastname: Dias
authors.forename: Maurício Reis
authors.initials: MR
authors.lastname: Bogo
authors.forename: Carla Denise
authors.initials: CD
authors.lastname: Bonan
mesh_terms: D015720:5'-Nucleotidase / Q000378:metabolism*; D000244:Adenosine Diphosphate / Q000378:metabolism; D000249:Adenosine Monophosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001921:Brain / Q000187:drug effects* / Q000201:enzymology; D002235:Carbofuran / Q000633:toxicity*; D002800:Cholinesterase Inhibitors / Q000633:toxicity*; D006868:Hydrolysis; D066298:In Vitro Techniques; D007306:Insecticides / Q000633:toxicity*; D008294:Malathion / Q000633:toxicity*; D008566:Membranes / Q000187:drug effects / Q000201:enzymology; D043583:Nucleoside-Triphosphatase / Q000378:metabolism*; D015027:Zebrafish
chemical_list: D002800:Cholinesterase Inhibitors; D007306:Insecticides; D000249:Adenosine Monophosphate; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D015720:5'-Nucleotidase; D043583:Nucleoside-Triphosphatase; D002235:Carbofuran; D008294:Malathion