Comparative study of toxicity and biochemical responses induced by sublethal levels of the pesticide azinphosmethyl in two fish species from North-Patagonia, Argentina

GUERREÑO M.; LÓPEZ ARMENGOL M.F.; LUQUET C; VENTURINO A

AQUATIC TOXICOLOGY

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2016 vol. 177 p. 365 - 372

0166-445X

Biochemical effects of azinphosmethyl (AZM), anorganophosphate pesticide, were determined in gill, brain and muscle tissues ofOdontesthes hatcheri and Jenynsia multidentata. The 96-htoxicity was first assessed, estimating lethal concentrations fifty (LC50) of 7and 30 μg L-1 AZM for O.hatcheri and J. multidentata,respectively. Considering the LC50, sublethal 96-h static exposures weredesigned for O. hatcheri (0.1-0.5 μg L-1AZM) and J. multidentata (5-10 μg L-1AZM)to determine biochemical endpoints. Brain acetylcholinesterase (AchE) was inhibited by AZM in both species, while the buffer enzyme carboxylesterase(CarbE) was not affected in this tissue. Conversely, muscular AchE was notaffected but CarbE was augmented by AZM. The enzymesglutathione reductase, glutathione-S-transferase and CarbE were significantlyinhibited in O. hatcheri gills but none of them was affected by AZM in J. multidentata gills compared tocontrol. GSH levels were augmentedin gills of both species in exposed fish compared to controls and in addition,lipid peroxidation was significantly increased in O. hatcheri gills. Ex vivohistochemical analysis of ROS by fluorescence microscopy was also performed in J. multidentata gills, indicating a significantincrease upon exposure to 10 µg L-1 AZM. Principalcomponent analyses (PCA) were applied, both to the species together orseparately. The general analysis demonstrated a clear separation of responsesin the two species. For O. hatcheri,the variable that explains the major variation in PC1 is gill catalase andbrain AchE in PC2. In J. multidentatain turn, the variable that explains the major variation in PC1 is brain AchEand total oxyradical scavenging capacity in PC2. The toxicity data andbiomarker responses obtained for both species were compared to environmentalconcentrations of AZM detected in superficial water from different points inthe Alto Valle region and risk quotients (RQ) were calculated. This approachindicated probable acute effects for O.hatcheri in river and irrigation channels (RQ > 0.1), while the risk wasunacceptable in drainage superficial water (RQ > 1). In contrast, J. multidentata showed minimal risk inriver or channel water (RQ < 0.1) and probable risk in drainage water (RQ = 0.75).We conclude that not only the differential susceptibility of both species toAZM is environmentally relevant, but also that the different biomarkersresponding in each case underlie particular pathways stressed by this agrochemical.