SERUM-B ESTERASES AS A NONDESTRUCTIVE BIOMARKER IN THE LIZARD GALLOTIA-GALLOTI EXPERIMENTALLY TREATED WITH PARATHION

Lizards (Gallotia galloti) were given either single or consecutive acu te oral treatments of the organophosphorus (OP) insecticide parathion in two different experiments. Brain, serum, and liver microsomal ester ase activities and liver microsomal monooxygenase activities were meas ured 6 and 24 h after the single acute treatment at each of four diffe rent doses (Experiment 1) or periodically up to 72 d after a number-of consecutive acute treatments at two different doses (Experiment 2). I nhibition of serum butyrylcholinesterase (BChE) and carboxylesterase a ctivities was observed in all treatment groups after 24 h and in the g roups treated with 2.5, 5, and 7.5 mg/kg of parathion 6 h after treatm ent. Brain acetylcholinesterase (AChE) was inhibited at all doses afte r 6 h but only at the highest dose after 24 h. Highly significant nonl inear 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 statistic ally significant. In Experiment 2, serum esterase activities recovered exponentially over a period of weeks. An Increase in the recovery tim e to normal esterase activity was observed after each consecutive acut e treatment. Brain AChE activity was inhibited at the end of consecuti ve administrations of parathion at the higher dose, and liver microsom al monooxygenase activity was inhibited at both doses. Symptoms of poi soning were observed in lizards treated with the higher dose of parath ion, 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 nond estructive biomarkers, serum ''B'' esterases, and the destructive biom arker. brain AChE, 6 and 24 h after exposure. These results suggest th at G. galloti should be an ideal bioindicator organism to assess OP ex posure in the Canary Islands instead of the birds commonly used for th is purpose.