Plasma B-Esterase Activities in European Raptors

Abstract

B-esterases are serine hydrolases composed of cholinesterases, including acetylcholinesterase (AChE) and butyrylcholinesterase (BChE), and carboxylesterase (CbE). These esterases, found in blood plasma, are inhibited by organophosphorus (OP) and carbamate (CB) insecticides and can be used as nondestructive biomarkers of exposure to anticholinesterase insecticides. Furthermore, B-esterases are involved in detoxification of these insecticides. In order to establish the level of these enzymes and to have reference values for their normal activities, total plasma cholinesterase (ChE), AChE and BChE activities, and plasma CbE activity were determined in 729 European raptors representing 20 species, four families, and two orders. The diurnal families of the Falconiforme order were represented by Accipitridae and Falconidae and the nocturnal families of the Strigiforme order by Tytonidae and Strigidae. Intraspecies differences in cholinesterase activities according to sex and/or age were investigated in buzzards (Buteo buteo), sparrowhawks (Accipiter nisus), kestrels (Falco tinnunculus), barn owls (Tyto alba), and tawny owls (Strix aluco). Sex-related differences affecting ChE and AChE activities were observed in young kestrels (2-3-mo-old) and age-related differences in kestrels (ChE and AChE), sparrowhawks (AChE), and tawny owls (ChE, AChE, and BChE). The interspecies analysis yielded a negative correlation between ChE activity and body mass taking into account the relative contribution of AChE and BChE to ChE activity, with the exception of the honey buzzard (Pernis apivorus). The lowest ChE activities were found in the two largest species, Bonelli's eagle (Hieraaëtus fasciatus) and Egyptian vulture (Neophron percnopterus) belonging to the Accipitridae family. The highest ChE activities were found in the relatively small species belonging to the Tytonidae and Strigidae families and in honey buzzard of the Accipitridae family. Species of the Accipitridae, Tytonidae, and Strigidae families were characterized by a BChE contribution that dominated the total ChE activity, while in the species of the Falconidae family, AChE activity dominated. With the exception of the barn owl, CbE activity (eserine-insensitive ␣-naphthyl acetate esterase [␣-⌵〈⌭] activity) in all species was almost absent or very low. The values obtained in this study for ChE, AChE, and BChE activities and the AChE:BChE ratios for buzzard, kestrel, barn owl, and tawny owl provide a good estimate of the normal values in free-living individuals of these European species. They can be used as a baseline to evaluate the effect of anticholinesterase insecticides in the field.

Serum and Plasma Cholinesterase Activity in the Cape Griffon Vulture (Gyps coprotheres)

“…Although the serum/plasma ChE activity was lower than that generally seen for mammals, the reference intervals we determined were similar to those for other vultures, including Lammergeier (Gypaetus barbatus) adults (6886195.1 U/L; Hernandez and Margalida 2010), and the Egyptian Vulture (Neophron percnopterus) (7096192 U/L; Roy et al 2005). Activities were also similar to those for Red-Tailed Hawks (Buteo jamaicensis) (7906162 U/L; Hooper et al 1989).…”

“…Van Wyk et al (1998) used the acetylthiocholine reaction, whereas we used the butyrylthiocholine method because it is readily available in South Africa. The results from the other bird species with similar activities were achieved using either the acetylthiocholine method (Hooper et al 1989;Roy et al 2005) or the butyrylthiocholine method (Hernandez and Margalida 2010). Another possible reason could be agerelated declines in plasma/serum ChE activity; a similar trend was reported for the Peregrine Falcon (Falco peregrinus; del Pilar Lanzarot et al 2001).…”

“…Brain ChE activity has typically been the assay used to establish diagnostic standards and determine poisoning due to ChE-inhibiting compounds postmortem; however, ChE activity can also be quantified using serum or plasma under clinical settings. Although in mammals the ChE is found within erythrocytes and plasma, in birds the enzyme is found within plasma and serum (Roy et al 2005). We estimated the plasma and serum activity of ChE in adult Cape Griffon Vulture (Gyps coprotheres), one of southern Africa's endangered vulture species.…”

Acute Toxicity and Cholinesterase Inhibition in Chicks Dosed Orally with Organophosphate Insecticides

“…The most important diagnostic or biomarker endpoint of OP exposure and poisoning is decreased ChE activity in the blood (erythrocytes, plasma or serum) and other tissues, brain in particular (3)(4)(5)(6)(7)(8). Birds have no ChE activity in erythrocytes; therefore, the extent of their exposure to and/or OP poisoning is based on ChE activity in plasma and nervous tissue (3,(9)(10)(11).…”

DEVELOPMENT OF REFERENCE RANGES FOR PLASMA TOTAL CHOLINESTERASE AND BRAIN ACETYLCHOLINESTERASE ACTIVITY IN FREE-RANGING CARNABY'S BLACK-COCKATOOS (CALYPTORHYNCHUS LATIROSTRIS)

“…Wide interspecies differences exist in avian plasma levels of AChE and other esterases (Roy et al 2005). It is recommended that species-specific reference ranges be used when attempting to diagnose anticholinesterase exposure and toxicoses (Hill 1988;Shimsoni et al 2012).…”