2,4-二氯苯氧乙酸对幼龄SD大鼠肝毒性的研究

Hepatotoxicity of 2,4-dichlorophenoxyacetic acid in young SD rats

目的:研究2,4-二氯苯氧乙酸(2,4-D)对幼龄SD大鼠肝毒性的影响及其相关机制。方法:SPF级刚断乳21 d的SD大鼠64只,随机分为3个2,4-D染毒组(18.125、36.250、72.500 mg/kg)和1个溶剂对照组(1%羧甲基纤维素溶剂),每天经口灌胃1次,连续染毒28 d。试验期间观察并记录大鼠的一般行为和体质量变化。染毒结束后,取肝脏计算湿质量及脏器系数;采用苏木精-伊红染色法(HE)对肝脏进行病理学检测;肝脏样品经处理后采用二硫二硝基苯甲酸(DTNB)直接法检测谷胱甘肽(GSH)活性,黄嘌呤氧化酶法检测总超氧化物歧化酶(T-SOD)活性,TBA法测定丙二醛(MDA)浓度;采用分光光度计测定肝组织细胞色素C浓度、Caspase-3、Caspase-9相对活性。结果:与对照组比较,72.500 mg/kg 2,4-D染毒组大鼠体质量增长下降(P<0.05),肝脏湿质量降低(P<0.05);病理结果显示72.500 mg/kg 2,4-D染毒组大鼠部分肝组织出现胆管增生,并伴有炎细胞浸润;与对照组相比,72.500 mg/kg 2,4-D染毒组肝匀浆中GSH活性降低(P<0.05),36.250和72.500 mg/kg 2,4-D染毒组T-SOD活性降低(P<0.05),肝匀浆MDA浓度升高(P<0.05);分光光度计检测结果显示36.250和72.500 mg/kg 2,4-D染毒组大鼠肝组织的细胞色素C含量升高(P<0.05),36.250和72.500 mg/kg 2,4-D染毒组Caspase-3、Caspase-9相对活性较对照组均增加(P<0.05)。结论:在本实验条件下,2,4-D可引起幼龄SD大鼠肝毒性的发生,其发生的途径可能是通过改变线粒体膜通透性,释放凋亡因子细胞色素C等来引发肝细胞凋亡,进而引起肝细胞的氧化损伤。

OBJECTIVE:To investigate the hepatotoxicity of 2,4-dichlorophenoxyacetic acid in young SD rats.METHODS:64 young SD rats with SPF grade were randomly divided into three 2,4-D inoculation groups(18.125,36.250,72.500 mg/kg)and a solvent control group(1%carboxymethyl cellulose).The rats were inoculated with the chemicals orally once a day for 28 days.After the exposure,their general behavior and weight changes were monitored,wet weights and viscera coefficients of the livers were calculated.Pathology of the livers were determined after their staining with hematoxylin-Eosin(HE).Activities of glutathione(GSH),total superoxide dismutase(T-SOD)and concentrations of malondialdehyde(MDA)were measured using the DTNB assay,and xanthine oxidase and TBA assays were conducted after liver samples were pretreated.Contents of cytochrome C,relative activities of Caspase-3 and Caspase-9 in liver tissues were determined by spectrophotometer.RESULTS:Compared with the control group,rats from the 72.500 mg/kg treatment group showed the following:body weight gains and liver wet weight were reduced significantly(P<0.05);parts of the livers had bile duct hyperplasia which were accompanied with inflammatory cell infiltration;GSH activities in the liver homogenates were decreased(P<0.05);and MDA concentrations were increased(P<0.05).In rats from both the 36.250 mg/kg and 72.500 mg/kg treatment groups,the activities of T-SOD were decreased(P<0.05);cytochrome C concentrations were increased(P<0.05);and the relative activities of caspase-3 and caspase-9 were increased(P<0.05).CONCLUSION:Under the conditions of this investigation,2,4-D was shown to induce hepatotoxicity in young SD rats.The toxicity was probably mediated by changing mitochondrial membrane permeability and releasing apoptotic factor to induce hepatocyte apoptosis,thereby causing oxidative damage to hepatocytes.