Department of Veterinary Medicine and Public Health, Sokoine University of Agriculture, Morogoro, Tanzania.
Ecotoxicology. 2010 Jun;19(5):855-63. doi: 10.1007/s10646-010-0466-3. Epub 2010 Feb 19.
The objective of this study was to investigate the response of acetylcholinesterase (AChE) activities in Clarias gariepinus in response to Organophosphates (Ops) and carbamate exposure. The AChE activities were determined in plasma, and eye and brain homogenates of unexposed and exposed fish using Ellman's method and 5,5'-dithiobis-2-nitrobenzoic acid (DTNB) chromophore. The baseline AChE activities in plasma, eyes and brain tissues in unexposed fish were comparable between males and females (P > 0.05). Concentrations of pesticides that inhibited 50% (IC(50)) of AChE activities in brain homogenates following in vitro exposures were 0.003, 0.03, 0.15, 190, 0.2, 0.003 and 0.002 microM for carbaryl, chlorfenvinphos, diazinon, dimethoate, fenitrothion, pirimiphosmethyl and profenofos, respectively. The in vivo dose-effect relationships were assessed using chlorfenvinphos and carbaryl at different concentrations that ranged from 0.0003 to 0.06 microM and 0.0005 to 0.05 microM, respectively. Acetylcholinesterase activities were comparable in plasma, and eye and brain homogenates from control and carbaryl-exposed fish. Following exposure of fish to chlorfenvinphos at concentrations above 0.03 microM, a significant inhibition of AChE activities in plasma (84%) and eye homogenate (50%) was observed. The AChE activities in brain homogenate were comparable between chlorfenvinphos-exposed fish and controls. Because carbaryl cause reversible inhibition of AChE activities was found to be more potent than chlorfenvinphos that cause irreversible inhibition following in vitro exposure. Contrary, carbaryl was less potent than chlorfenvinphos after in vivo exposure possibly due to more rapid biotransformation of carbaryl than chlorfenvinphos. Findings from this study have demonstrated that inhibition of AChE activity in C. gariepinus is a useful biomarker in assessing aquatic environment contaminated by anticholinesterases.
本研究旨在探讨鱼类乙酰胆碱酯酶（AChE）对有机磷（Ops）和氨基甲酸酯暴露的反应。采用 Ellman 法和 5,5'-二硫代双-2-硝基苯甲酸（DTNB）显色法，在未暴露和暴露鱼类的血浆、眼睛和脑匀浆中测定 AChE 活性。未暴露鱼的血浆、眼睛和脑组织中的基线 AChE 活性在雄性和雌性之间无差异（P > 0.05）。体外暴露后，抑制脑匀浆 AChE 活性 50%（IC（50））的农药浓度分别为 0.003、0.03、0.15、190、0.2、0.003 和 0.002μM，用于甲萘威、氯芬磷、二嗪农、乐果、毒死蜱、丙溴磷和丙硫磷。使用不同浓度的氯芬磷和甲萘威（分别为 0.0003 至 0.06μM 和 0.0005 至 0.05μM）评估体内剂量-效应关系。与甲萘威暴露的鱼相比，暴露于氯芬磷的鱼的血浆和眼匀浆中的 AChE 活性相当。在鱼类暴露于 0.03μM 以上的氯芬磷后，血浆（84%）和眼匀浆（50%）中的 AChE 活性受到显著抑制。氯芬磷暴露鱼与对照组之间的脑匀浆 AChE 活性相当。由于甲萘威引起的 AChE 活性的可逆抑制比体外暴露后引起不可逆抑制的氯芬磷更为有效。相反，在体内暴露后，甲萘威的效力比氯芬磷低，可能是因为甲萘威比氯芬磷更容易生物转化。本研究结果表明，抑制鱼类 AChE 活性是评估受抗胆碱酯酶污染的水生环境的有用生物标志物。
