RESUMO
The aim of this work was to study the pharmacokinetic behavior and the inhibitory effect of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) activities of chlorpyrifos (CPF) in steer cattle after pour-on administration. Determination of cholinesterase activity in plasma and erythrocyte was carried out according to Ellman kinetic method. CPF was analyzed by gas chromatography. AChE was the predominant form of cholinesterase analyzed, with low levels of BChE in plasma. Following the treatment with CPF, the maximum inhibitory effect on AChE or BChE were 50.88 +/- 11.57 and 42.66 +/- 12.01%, respectively. The chlorpyrifos plasma concentrations observed were low and they presented a high variability. Chlorpyrifos peak plasma concentration (10.42 +/- 4.76 micro g/L) was reached at 8.42 +/- 13.97 h. The pesticide was not detected in plasma after 48 h post treatment. The values of area under the curve (AUC) were 118.48 +/- 87.46 micro g x h/L and mean resistance time (MRT) were 13.38 +/- 10.41 h. The pour-on exposure to the organophosphate chlorpyrifos significantly reduced AChE and BChE activity in steer cattle and the recovery was not reached on 50 days post-treatment.
Assuntos
Acetilcolinesterase/sangue , Administração Tópica , Butirilcolinesterase/sangue , Clorpirifos/administração & dosagem , Eritrócitos/efeitos dos fármacos , Inseticidas/administração & dosagem , Animais , Bovinos , Cromatografia Gasosa , Eritrócitos/enzimologia , Eritrócitos/metabolismo , CinéticaRESUMO
The aim of this work was to study the pharmacokinetic behaviour and the inhibitory effect on acetylcholinesterase and butyrylcholinesterase activities of chlorpyrifos in male and female cattle after pour-on administration. Determination of cholinesterase activity in plasma and erythrocyte was carried out according to Ellman kinetic method. The mean baseline activities were 9338.39 +/- 1331.61 and 13220.69 +/- 2274.18 to acetylcholinesterase and 624.65 +/- 39.32 and 641.68 +/- 88.08 IU/L to butyrylcholinesterase in females and males, respectively. Acetylcholinesterase was the predominant form of cholinesterase analyzed, with low levels of butyrylcholinesterase. The basal acetylcholinesterase activities of the bulls were significantly greater than those of cows. The inhibitory effect of topical chlorpyrifos administration was lower on butyrylcholinesterase than on acetylcholinesterase. Chlorpyrifos peak plasma concentration (male:10.920 +/- 4.18; female:12.12 +/- 3.88 microg/L) were reached at 11.92 +/- 9.19 and 8.17 +/- 7.67 h in male and female, respectively. The values of area under curve were 185.96 +/- 168.45 and 278.89 +/- 270.00 microg h/L and mean residence time were 13.95 +/- 8.10 and 14.90 +/- 9.80 h in male and female, respectively.