Plasma phenylacetate and 1-naphthyl acetate hydrolyzing activities of wild birds as possible non-invasive biomarkers of exposure to organophosphorus and carbamate insecticides

Organophosphorus and carbamate insecticides inhibit the carboxylesterases found in plasma. Therefore, these carboxylesterases might be used as biomarkers of exposure to these insecticides. This work initiates the characterization of the phenylacetate (PA) and 1-nafthylacetate (NA) hydrolyzing activities (PAase and NAase) in the plasma of 11 different wild bird species and aims to determine their suitability as biomarkers of exposure. PAase activity values, expressed as μmol product/30 min/mL plasma, ranged between 38 ± 2.3 (black vulture) and 27 ± 0.85 (barn owl), while NAase values ranged between 6.0 ± 5.2 (griffon vulture) and 38 ± 0.85 (barn owl). In all assayed species, NAase was between 1.1 and 2.8 times higher than the corresponding PAase. PAase and NAase of chicken white stork were 1.6 and 1.7 times higher, respectively, than the corresponding activities of adult individuals. Nocturnal raptors, eagle owl and barn owl, exhibited PAase and NAase between 1.3 and 8.0 times higher than activities exhibited by diurnal raptors (Montagu's harrier, common buzzard, booted eagle, Spanish imperial eagle, black kite, griffon vulture and black vulture). Data presented in this work suggest that plasma PAase and NAase of the studied birds might be used as biomarkers of exposure to organophosphorus and carbamate insecticides, although further studies of inhibition of these activities are still needed.