Serum B Esterases as a Nondestructive Biomarker in the Lizard Gallotia Galloti Experimentally Treated With Parathion

Abstract

Abstract-Lizards (Gallotia galloti) were given either single or consecutive acute oral treatments of the organophosphorus (OP) insecticide parathion in two different experiments. Brain, serum, and liver microsomal esterase activities and liver microsomal monooxygenase activities were measured 6 and 24 h after the single acute treatment at each of four different doses (Experiment 1) or periodically up to 72 d after a number of consecutive acute treatments at two different doses (Experiment 2). Inhibition of serum butyrylcholinesterase (BChE) and carboxylesterase activities was observed in all treatment groups after 24 h and in the groups treated with 2.5, 5, and 7.5 mg/kg of parathion 6 h after treatment. Brain acetylcholinesterase (AChE) was inhibited at all doses after 6 h but only at the highest dose after 24 h. Highly significant nonlinear correlations, based on a piecewise linear regression model, were obtained between brain AChE activity and serum esterase activities at two sampling times after the single acute treatment. Liver microsomal carboxylesterase was found to be induced at the lower doses 6 and 24 h after treatment. Liver microsomal monooxygenase activity was higher 6 h after treatment than at 24 h, but the difference was not statistically significant. In Experiment 2, serum esterase activities recovered exponentially over a period of weeks. An increase in the recovery time to normal esterase activity was observed after each consecutive acute treatment. Brain AChE activity was inhibited at the end of consecutive administrations of parathion at the higher dose, and liver microsomal monooxygenase activity was inhibited at both doses. Symptoms of poisoning were observed in lizards treated with the higher dose of parathion, but no mortality was recorded. Two main conclusions can be drawn: (1) serum esterase activities recovered extremely slowly after acute treatment with parathion and even more slowly after consecutive acute treatments, and (2) there was a nonlinear correlation between the nondestructive biomarkers, serum ''B'' esterases, and the destructive biomarker, brain AChE, 6 and 24 h after exposure. These results suggest that G. galloti should be an ideal bioindicator organism to assess OP exposure in the Canary Islands instead of the birds commonly used for this purpose.

Lizard cholinesterases as biomarkers of pesticide exposure: Enzymological characterization

“…Serum BChE activity is suggested to be a better biomarker than serum AChE activity for assessing exposure to anti‐ChE pesticides. The high activity (on BuSCh) of serum BChE with respect to AChE, together with the previously reported [26] response to the inhibitory effect from OPs (high sensitivity and slow recovery rate after acute OP exposure), justify the use of serum BChE activity as an acceptable biomarker of pesticide exposure in G. galloti .…”

“…Furthermore, optimal conditions for ChE measurements in G. galloti are in the pH range of 7.5 to 8.0 and the substrate concentrations of 5 mM (serum and brain AChE) or 10 mM (serum BChE) (Table 2). Although not examined in this study, an incubation temperature of 25°C was considered as optimal for ChE measurements, as previously reported for this lizard species [26]. Likewise, data on the most favorable conditions for determining ChE activity in some species of aquatic invertebrates and fish are also reported in Table 2 for comparison.…”

“…Data on toxic effects of OP pesticides on the lizard Gallotia galloti provide evidence that this organism shows an array of desirable features that make it a suitable sentinel of pollution. Serum BChE activity of G. galloti is a very sensitive biomarker of pesticide exposure, with a slow recovery rate (over weeks) after acute OP exposure [26]. In addition, serum BChE activity shows a significant relationship with brain AChE activity after acute OP exposure, which appears to be dependent on the type of OP [27].…”

A logical starting point for developing priorities for lizard and snake ecotoxicology: A review of available data

“…In addition to some older studies, all of the recent studies on the effects and accumulation of pesticides on lizards have been conducted in Australia, Africa, and Europe [7,10,15, 25,26]. These recent studies are promising because the sublethal effects of organic contaminants were studied, and these effects were linked to exposure concentrations.…”

Reviews of Environmental Contamination and Toxicology

“…In addition, laboratory studies with Gallotia galloti found that carboxylesterase activity was inhibited for a longer duration than was brain acetylcholinesterase activity following parathion exposure, suggesting that carboxylesterase activity was a superior biomarker (Sanchez et al 1997b). However, field studies with Gallotia galloti in the Canary Islands found that carboxylesterase and acetylcholinesterase activity were essentially equally inhibited following exposure to the OP trichlorphon, whereas butyrylcholinesterase activity was only slightly affected (Fossi et al 1995).…”