Enzymatic activity measured in the freshwater snail Chilina gibbosa hemolymph is more sensitive to AZM than in whole tissue homogenates

COSSI, PAULA FANNY; LUQUET, CARLOS; HERBERT, LUCILA THOMSETT; KRISTOFF, GISELA

Córdoba

Congreso; VI Congreso Argentino de la Sociedad de Toxicología y Química Ambiental de Argentina (SETAC Argentina); 2016

Chilina gibbosa is a freshwater snail endemic to South America, found in rivers, lakes and reservoirs of the Río Negro and Neuquén provinces. It is a good model organism for ecotoxicity bioassays; adults are easy to collect and handle, it is found in shallow waters, it has an aggregated dispersion pattern, its reduced ability to excrete pollutants makes it susceptible to negative effects at low environmental concentrations of toxicants, and its limited mobility and restricted habitat mean that it is effectively exposed to any pollutant present in the environment. In the Upper Valley of Río Negro and Neuquén, agriculture is one of the main economic activities and large amounts of pesticides, such as the organophosphate azinphos-methyl (AZM), are applied on different crops and have been found in the surrounding water.In this study, our aim was to characterize the effect of an acute 48h exposure to 20 µg L-1 AZM on enzymatic activity in C. gibbosa hemolymph. We extracted the hemolyph with a syringe and measured the activity of cholinesterases (ChEs), carboxilestersases (CEs) using p-nitrophenyl acetate (p-NPA) and p-nitrophenyl butyrate (p-NPB) as substrates, and glutathione S-transferase (GST). ChE was strongly inhibited in hemolymph (94%) of exposed animals. CE activity measured with p-NPB and GST activity were 47% and 89% higher after AZM exposure, respectively. CE activity measured with p-NPA was not affected.We compared these results with previous studies from our laboratory that have focused on characterizing AZM effects in whole tissue homogenates. ChE inhibition is higher (94%) in hemolymph than in homogenates (85%). Remarkably, whilst we found higher activities for CE measured with p-NPB and GST in hemolymph of exposed animals, no differences were found in homogenates. No differences were found for CE activity measured with p-NPA in either homogenates or hemolymph.In conclusion, ChE, CE and GST enzymatic activity measured in C. gibbosa hemolymph is more sensitive to AZM than the same activities measured in whole tissue homogenates. On the one hand, this means that, together with ChE activity, CE and GST activities measured in hemolymph could be included as sensitive biomarkers for this species, as their induction implies they could be helping to remove available AZM. On the other hand, it indicates that techniques could be adapted to obtain snail hemolymph in such a manner and reduced volumes so as to allow the animals to recover after extraction.