SEASONAL VARIATIONS IN THE DOSE-RESPONSE RELATIONSHIP OF ACETYLCHOLINESTERASE ACTIVITY IN FRESHWATER FISH EXPOSED TO CHLORPYRIFOS AND GLYPHOSATE

DAISSY L. BERNAL-REY; RENATA J. MENÉNDEZ-HELMAN; MARIA DOS SANTOS AFONSO; CECILIA G. CANTERA; DAISSY L. BERNAL-REY; RENATA J. MENÉNDEZ-HELMAN; MARIA DOS SANTOS AFONSO; CECILIA G. CANTERA

ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY

ACADEMIC PRESS INC ELSEVIER SCIENCE

Lugar: Amsterdam; Año: 2019 vol. 187

0147-6513

The application of pesticides has been increased in Latin American countries. In particular, the herbicide glyphosate [N- (phosphonomethyl) glycine; PMG] and the insecticide chlorpyrifos [O, O-diethyl O- (3,5,6-trichloro-2-pyridinyl) -phosphorothioate, CPF] are widely used in the region. Therefore, it is necessary to characterize the toxicity of these pesticides on non-target species. The use of biomarkers as a tool to assess responses of organisms exposed to pollutants requires the understanding of the natural fluctuation and the dose-response relationship. In the present work, the effect of the exposure to PMG and CPF on the acetylcholinesterase activity (AChE, biomarker of neurotoxicity) in Cnesterodon decemmaculatus, a native teleost, was evaluated in different environmental conditions. Semi-static bioassays of acute toxicity were carried out under controlled conditions during the four weather seasons of the year using animals of homogeneous size. Circannual rhythms in the basal levels of AChE activity in homogenates of the anterior section were confirmed. Statistically significant average inhibition of AChE activity (47.1 ± 0.7% for 1 µg CPF × L-1; 69.7 ± 2.5% for 5 μg CPF × L-1; 23.1 ± 1.1% for 1 mg PMG × L-1 and 32.9 ± 3.3% for 10 mg PMG × L-1) was determined during summer, winter and spring weather seasons. On the other hand, a greater susceptibility of the animals to exposure to both pesticides during the autumn season was observed (inhibition of 55.4 ± 0.6% for 1 µg CPF × L-1; 81.9 ± 3.3% for 5 μg CPF × L-1; 41.4 ± 1.7% for 1 mg PMG × L-1 and 61.1 ± 0.3% for 10 mg PMG × L-1). A different sensitivity of the enzyme between seasons was evaluated by in vitro tests. The inhibition pattern for chlorpyrifos-oxon (CPF-oxon, the active metabolite of CPF) was not affected when test was performed using homogenates of unexposed specimens of summer or autumn. Otherwise, PMG in vitro inhibitory effect was not observed in a wide range of concentrations.The results confirm that AChE activity is a sensitive biomarker for exposure to CPF and PMG, even at environmentally relevant concentrations. Finally, this work highlights the existence of seasonal variations in the dose-response relationship, which could be due to variations in the metabolism of the pollutants.