4种鱼类肝脏细胞色素P450对毒死蜱、对硫磷及马拉硫磷的脱硫代谢

Desulfuration of Chlorpyrifos, Parathion, and Malathion by Hepatic Cytochrome P450 in Four Species of Fish

以毒死蜱、对硫磷及马拉硫磷为供试农药,以斑马鱼、剑尾鱼、麦穗鱼及太阳鱼为供试生物,研究了3种农药对4种鱼的急性毒性,4种鱼肝细胞色素P450对3种农药的脱硫代谢作用及两者之间的相关性。结果表明,毒死蜱对于上述4种鱼的96hLC50分别为1.94、0.171、0.0273、0.0681mg·L-1;对硫磷为2.6、0.0559、1.78、1.02mg·L-1;马拉硫磷为7.07、0.907、6.03、0.172mg·L-1。4种鱼肝脏P450对于毒死蜱代谢的Vmax/Km值分别为1.67×104、2×104、5×104、2×104min-1;对于对硫磷代谢的Vmax/Km值分别为2×104、5×105、1.11×105、1.43×105min-1;对于马拉硫磷的值分别为5×103、5×104、2.5×103、1.67×104min-1。96hLC50值与Vmax/Km值大体呈负相关,其中毒死蜱的相关性较弱,对硫磷及马拉硫磷的相关性较强(R2值分别为0.2181、0.8490、0.5102)。研究结果说明P450在鱼类耐药性形成过程中发挥了阻碍作用。

Fish is common in water and is suitable for identifying the presence of chemical pollutants in water bodies. For evaluating efficiency of oxidative metabolism in determination of sensitivity of fish to organothiophosphorus insecticides, in vitro desulfuration of three insecticides, i.e. chlorpyrifos, parathion, and malathion, by hepatic cytochrome P450 was measured using four species of fish, i.e. Danio rerio, Xiphophorus helleri, Pseudorasbora parva, and Lepomis gibbosus as surrogates, and the activity was compared with sensitivity of corresponding fish towards the insecticides. Result of the study indicated that 96 h LC50 of chlorpyrifos for the Danio rerio, the Xiphophorus helleri, the Pseudorasbora parva, and the Lepomis gibbosus was estimated to be 1.94, 0.171, 0.027 3 mg·L^-1 and 0.068 1 mg·L^-1, respectively, and 96 h LC50 of parathion for the four species of fish was estimated to be 2.6, 0.055 9, 1.78 mg·L^-1 and 1.02 mg·L^-1, respectively. As for malathion, the 96 h LC50 for the four species of fish was estimated to be 7.07, 0.907, 6.03 mg·L^-1 and 0.172 mg·L^-1 respectively. Desulfuration activity of hepatic cytochrome P450, as scaled with Vmax/Km, was estimated to be 1.67×10^4, 2×10^4, 5×10^4 min^-1 and 2×10^4 min^-1, respectively, for chlorpyrifos, and the activity was estimated to be 2×10^4, 5×10^5, 1.11×10^5 min^-1 and 1.43×10^5 min^-1, respectively, for parathion. For malathion the activity was estimated to be 5×10^3, 5×10^4, 2.5×10^3 min^-1 and 1.67×10^4 min^-1, respectively. A negative correlation was found between LC50 and Vmax/Km. The value of R2 was estimated to be 0.218 1, 0.894 0 and 0.510 1, respectively for chlorpyrifos, parathion, and malathion. Result of the study suggested that cytochrome P450 played a negative role in creating tolerance of fish to organothiophosphorus insecticides.