Resistance in cholinesterase activity after an acute and subchronic exposure to azinphos-methyl in the freshwater gastropod Biomphalaria straminea

BIANCO, K.; OTERO, S.; BALAZOTE OLIVER, A.; NAHABEDIAN, D.; KRISTOFF, G.

ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY

ACADEMIC PRESS INC ELSEVIER SCIENCE

Lugar: Amsterdam; Año: 2014 vol. 109 p. 85 - 92

0147-6513

Organophosphorous and carbamates insecticides are ones of the most popular classes of pesticides used in agriculture. Its success relies on their high acute toxicity and rapid environmental degradation. These insecticides inhibit cholinesterases (ChEs) and cause severe effects on aquatic non-target species, particularly in invertebrates. Since the properties of ChEs may differ between species, it is necessary to characterize them before they are used as biomarkers. Also organophosphorous and carbamates inhibit carboxylesterases (CES) and the use of both enzymes for biomonitoring has been suggested. Azinphos-methyl is an organophosphorous insecticide used in several parts of the word. In Argentina it is the most applied insecticide in the fruit production in the north Patagonian region. It was detected with the highest frequency in superficial and groundwater of the region. The aim of the present work was to characterize ChE and CE activities of Biomphalaria straminea, a freshwater gastropod native of South America. These enzymes, together with neurotoxicity, lethality an protein content, were evaluated herein after as sensitive biomarkers of acute and subchronic exposure to environmental concentrations of azinphos-methyl. As in most invertebrates, acetylthiocholine was the preferred hydrolyzed substrate of B. straminea ChE, followed by propionylthiocholine and being butyrylthiocholine hydrolysis very low. CES activity was one order of magnitude higher than ChE activity. A greater efficiency was obtained using acetylthiocholine (ChE) and p-nitrophenyl butyrate (CES). Acute exposure to azinphos-methyl did not cause any inhibition of ChE until 10 mg L-1 used. CES towards p-NPB was inhibited by azinphos-methyl protecting ChE and therefore, protecting the organism from neurotoxicity. Subchronic exposure to environmental concentrations of azinphos-methyl produced a decrease in survival, protein content and CES activity. This work confirms the advantages of measuring ChEs and CES jointly in aquatic biomonitoring of pesticide contamination. B. straminea ChE is not a sensible biomarker; however others toxic effect were produced mainly at subchronic exposure. This becomes relevant in order to find more sensitive biomarkers and new strategies to protect non-target aquatic organisms from pesticide contamination.