Evaluating reptile exposure to cholinesterase‐inhibiting agrochemicals by serum butyrylcholinesterase activity

Abstract

Blood samples from lizards (Gallotia galloti) collected from two agricultural areas (Las Galletas and Punta del Hidalgo) and two reference areas on the Island of Tenerife (Canary Islands, Spain) were analyzed for butyrylcholinesterase (BChE) activity. Serum BChE activity was characterized first by in vitro experiments using selective substrates and inhibitors. Of the total cholinesterase (ChE) activity, 74% could be attributed to BChE activity. This portion of the total ChE activity was inhibited dose dependently by tetraisopropyl pyrophosphoramide and hydrolyzed the substrate butyrylthiocholine iodide. No enzyme inhibition was observed at high substrate concentration. Twenty-one lizards collected from agricultural sampling sites showed significant inhibition (p < 0.001) of BChE activity (mean +/- standard deviation [SD] of 4.66 +/- 2.63 micromol/min/ml for lizards from Las Galletas and 5.13 +/- 1.48 for lizards from Punta del Hidalgo) compared with BChE activity for lizards from the reference sites (6.35 +/- 1.75 micromol/min/ ml). Las Galletas had the highest number of lizards (22%) with significantly inhibited BChE activity. In vitro assays showed that 10(-4) M pyridine-2-aldoxime methochloride (2-PAM) reactivated dichlorvos- or paraoxon-inhibited BChE activity within a 60-min incubation period. Almost all serum samples with depressed BChE activity that were collected from lizards from agricultural areas responded to 2-PAM reactivation of enzyme activity (8-60% increase in enzyme activity). Reactivation by treatment with 2-PAM confirmed that the depression of BChE activity was attributable to organophosphorus (OP) compounds. Evaluation of BChE activity levels and the chemical reactivation of serum BChE activity in G. galloti using 2-PAM was found to be a sensitive indicator of G. galloti exposure to OP compounds.

B-esterase activities and blood cell morphology in the frog Leptodactylus chaquensis (Amphibia: Leptodactylidae) on rice agroecosystems from Santa Fe Province (Argentina)

“…These authors reported that serum BChE activity of herpetofauna previously inhibited by OP did not recover totally in the presence of 2-PAM. Likewise, Sánchez-Hernández (2003) and Sánchez-Hernández et al (2004) observed similar increments of BChE activity reactivation after exposure to pesticides in Gallotia galloti (between 8 and 60%) and G. galloti palmae (between 5 and 53%) from agroecosystems. Accordingly, Parsons et al (2000) and Iko et al (2003) indicated that chemical reactivation of plasma phosphorylated ChE activity has been used for complementary diagnosis of OP intoxication.…”

Plasma B-esterase and glutathione S-transferase activity in the toad Chaunus schneideri (Amphibia, Anura) inhabiting rice agroecosystems of Argentina

“…This was corroborated by the 2-PAM reactivation assay, which enabled us to identify organophosphates (OPs) as the agrochemicals responsible for plasma BChE depression in the animals collected from the agricultural sites; this suggestion do not, however, rule out the possibility that carbamates (CBs) also were involved. Chemical reactivation of plasma phosphorylated ChE activity has been used for complementary diagnosis of OP intoxication in birds (Parson et al 2000;Iko et al 2003) and reptiles (Sánchez-Hernández, 2003;Sánchez-Hernández et al 2004) (Table 1). Our data show that OP pesticides are an important class of pesticide to amphibians in rice fields.…”

Development and validation of a simple assay for the determination of cholinesterase activity in whole blood of laboratory animals

“…BChE, mainly present in plasma, generally hydrolyzes butyrylthiocholine (BTC) at a higher rate than ATC and is not inhibited by excess substrate. AChE and BChE activities in blood are considered biomarkers of organophosphate (OP) pesticide or nerve agent exposure, because these agents inhibit both cholinesterases (ChEs; Coye et al ., ; Lotti, ; Sanchez‐Hernandez, ; Wilson et al ., ). Therefore, exposure to OP nerve agents and pesticides is normally assessed by measuring ChE activity in blood, and hence there is an urgent need for a simple, rapid, reliable and reproducible method for the accurate determination of both AChE and BChE activities in whole blood.…”