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

HERBERT, L.; COSSI, P.; LUQUET, C.; KRISTOFF, G.

Córdoba

Congreso; VI Congreso SETAC Capítulo Argentino; 2016

SETAC Capítulo Argentina

Chilina gibbosa is a freshwater snail endemic to South America, especially abundant in southern Chile and Argentina that can be readily 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, found in shallow waters, in an aggregated dispersion pattern, its limited mobility and ability to excrete pollutants may result in several negative effects at low environmental concentrations of toxicants, and its reduced habitat ensures its effective exposure to any pollutant present in the environment. Precisely in the Upper Valley of Río Negro and Neuquén, agriculture is one of the main economic activities and large amounts of pesticides are applied on different crops and have been found in the surrounding water. Previous studies from our laboratory have focused on the characterization of C. gibbosa response to an acute exposure to azinphos-methyl (AZM, a pesticide used in the Upper Valley), based on the activity of cholinesterases (ChEs), carboxilestersases (CEs) measured using p-nitrophenyl acetate (p-NFA) and p-nitrophenyl butyrate (p-NFB) as substrates, and glutathione S-transferase (GST) activity. Measurements were carried out on whole tissue homogenates. In this study, our aim was to characterize the effect of an acute 48h exposure to AZM on enzymatic activity in C. gibbosa hemolymph. ChE activity was strongly inhibited in hemolymph (94%), as in homogenates (85%). CE activity measured with p-NFB was 47% higher in hemolymph of exposed animals. No differences had been found when measured in homogenates. No differences where found for CE activity measured with p-NFA, which coincides with homogenate results. GST activity in hemolymph, on the other hand, was 89% higher in exposed animals, whilst no differences had been found when measured in homogenates.In conclusion, ChE, CE and GST enzymatic activity measured in C. gibbosa hemolymph is more sensitive to AZM than the same enzymatic activity 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.