2,3,7,8-四氯二苯并二恶英对SD大鼠肝脏SOD、GST、MDA影响的实验研究

目的　研究 2 ,3 ,7,8 四氯二苯并二恶英 (TCDD)对SD大鼠肝脏SOD、GST、MDA的影响。方法　把 5 0只雌性SD大鼠随机分为 10组 :染毒 2 4h组 (染毒剂量为 :0 0 1、 0 1、 1、 10、 5 0 μg/kg)、染毒 2 4h对照组 ;染毒72h组 (染毒剂量为 :0 1、 1、 10 μg/kg)、染毒 72h对照组 ,每组 5只。采用一次性腹腔注射染毒 ,测定其肝脏中SOD、GST的活性和MDA的含量。结果　染毒 2 4h后 ,与对照组相比 ,各染毒组SOD活力有所下降 ,但差异无显著性 ;各染毒组GST活力都有所增加 ,但只有 5 0 μg/kg组差异有显著性 (P <0 0 5 ) ,且染毒剂量与GST活力之间有剂量 效应关系 ;各染毒组MDA含量都有所增加 ,其中 10、 5 0 μg/kg组差异有显著性 (P <0 0 5 ) ,且染毒剂量与MDA含量之间存在剂量 效应关系。染毒 72h后 ,与对照组相比 ,各染毒组SOD活力均显著下降 (P <0 0 5 ) ,且染毒剂量与SOD活力之间有剂量 效应关系 ;各染毒组GST活力都有所增加 ,但差异无显著性 ;各染毒组MDA含量都有所增加 ,其中 1、10 μg/kg组差异有显著性 (P <0 0 5 ) ,且染毒剂量与MDA含量之间存在剂量 效应关系。 结论　急性染毒后 ,TCDD对SD大鼠的肝脏具有脂质过氧化作用 ,引起MDA含量增加 ,SOD活力降低 ,TCDD能诱导GST的活力 ,但诱导作用     

哺乳期暴露2,3,7,8-四氯二苯并-p-二(噁)英的子代小鼠生殖发育以及肺组织CYP1A1水平

目的 探讨哺乳期暴露2,3,7,8-四氯二苯并-P-二(噁)英(TCDD)对子代小鼠生长发育及细胞色素P4501A1(CYP1A1)表达的影响.方法 采用清洁级昆明小鼠,设40μg/kg和20μg/kg TCDD染毒组,并分设相应的两个溶剂对照组及-个动物空白对照组.每组母鼠3只,仔鼠25～28只.母鼠分娩后的第1、3、5天腹腔注射TCDD,子代小鼠通过乳汁暴露于TCDD.观察不同生长期仔鼠的体重改变和生殖系统发育等.仔鼠生后第35天被处死,采用免疫组化法分析肺组织CYP1A1的表达.结果 TCDD染毒组的仔鼠体重明显降低,雌性仔鼠的阴道平均开放时间明显缩短,雄性仔鼠的睾丸平均下降时间明显延长.TCDD染毒组的肺泡结构紊乱,炎症细胞浸润,肺泡壁增厚水肿,CYP1A1表达量明显升高,并且雌性仔鼠的肺组织反应比雄性仔鼠严重.而对照组中雌雄间差异没有显著性.结论 单一哺乳期暴露于TCDD可使子代小鼠体重下降,雌性仔鼠性成熟提前,雄性仔鼠性成熟延缓.仔鼠肺组织CYP1A1表达明显增加,并存在性别差异.     

2,3,7,8-四氯二苯-p-二(口恶)英对雌性小鼠血浆维生素A、E的影响

目的了解2,3,7,8-四氯二苯-p-二(口恶)英(TCDD)对雌鼠血浆维生素A、E水平的影响.方法将实验昆明种雌性小鼠24只,随机分为染毒高(100 μg/kg)、中(10 μg/kg)、低(1 μg/kg)剂量和空白对照4组,腹腔注射染毒.48 h后对实验小鼠取血,离心后取上层血浆,用无水乙醇沉淀蛋白,加环己烷萃取后,使用荧光分光光度仪在不同波长下测定其荧光值,计算出维生素A、E浓度,进行统计分析.结果对照及染毒剂量低、中、高4组中小鼠血浆维生素A的平均水平差异无显著性(P＞0.05);血浆维生素E的平均水平差异有显著性(P＜0.05),对照组与低剂量组之间维生素E的浓度水平差异无显著性,但与中、高剂量组之间维生素E的浓度水平差异都有显著性(P＜0.05).结论在此实验条件下,尚不能够认为TCDD对雌鼠血浆维生素A的水平有影响,但对维生素E的水平有一定影响.     

邻苯二甲酸二丁酯和邻苯二甲酸二(2-乙基己基)酯联合染毒对雄性大鼠肝脏P450酶的影响

目的探讨邻苯二甲酸二丁酯(DBP)和邻苯二甲酸二(2-乙基己基)酯(DEHP)联合染毒对雄性大鼠肝脏P450酶的影响。方法将20只健康清洁级成年SD雄性大鼠随机分为4组,分别为阴性对照(玉米油)组、DBP(1/20LD50,1.0g/kg)染毒组、DEHP(1/20LD50,1.7 g/kg)染毒组和DBP(1.0 g/kg)+DEHP(1.7 g/kg)染毒组,每组5只。采用灌胃方式进行染毒,每天1次,连续染毒7 d。末次染毒24 h后测定细胞色素P450酶总活力、CYP1A1活力、CYP2E1活力、CYP3A活力。结果 DBP和DEHP联合染毒可使肝脏脏器系数升高,交互作用均有统计学意义(P0.05),表现为协同作用;均可诱导上述4种酶活力增加,对肝细胞色素P450酶总活力、CYP1A1活力、CYP3A均存在协同作用(P0.05);对CYP2E1活力存在拮抗作用(P0.05)。结论 DBP和DEHP联合染毒对雄性大鼠肝脏P450酶存在交互作用。     

氯化消毒饮用水有机提取物对大鼠肝脏芳香烃受体和相关基因表达的影响

目的探讨氯化消毒饮用水水样中有机提取物染毒对大鼠肝脏芳香烃受体(aryl hydrcarbon receptor,AhR)和相关基因表达的影响。方法于2012年7—9月(丰水期)采集贵阳市某地水厂的管网末梢水水样并制备有机提取物。将40只清洁级SD大鼠随机分为4组,分别为对照(玉米油)组和5、20、80 L/kg饮用水有机提取物染毒组,每组10只,雌雄各半。采用经口灌胃方式进行染毒,每天1次,连续染毒12周。采用实时荧光定量PCR法检测肝脏中Ah R、热休克蛋白(HSP90)、芳香烃受体核转位蛋白(ARNT)和细胞色素1A2(CYP1A2)mRNA的表达水平,采用Western Blot法检测肝脏中AhR、HSP90、ARNT与CYP1A2蛋白的表达水平。结果与对照组比较,5、20、80 L/kg饮用水有机提取物染毒组大鼠肝脏中HSP90的mRNA和蛋白表达水平均增高,20、80 L/kg组大鼠肝脏中AhR、ARNT与CYP1A2 mRNA和蛋白的表达水平均增高,差异有统计学意义(P0.05)。结论在本实验条件下,氯化消毒饮用水有机提取物暴露可活化AhR通路。     

2,3,7,8-四氯二苯-p-二英对雌性小鼠血浆维生素A、E的影响

目的了解2,3,7,8-四氯二苯-p-二(口恶)英(TCDD)对雌鼠血浆维生素A、E水平的影响.方法将实验昆明种雌性小鼠24只,随机分为染毒高(100 μg/kg)、中(10 μg/kg)、低(1 μg/kg)剂量和空白对照4组,腹腔注射染毒.48 h后对实验小鼠取血,离心后取上层血浆,用无水乙醇沉淀蛋白,加环己烷萃取后,使用荧光分光光度仪在不同波长下测定其荧光值,计算出维生素A、E浓度,进行统计分析.结果对照及染毒剂量低、中、高4组中小鼠血浆维生素A的平均水平差异无显著性(P＞0.05);血浆维生素E的平均水平差异有显著性(P＜0.05),对照组与低剂量组之间维生素E的浓度水平差异无显著性,但与中、高剂量组之间维生素E的浓度水平差异都有显著性(P＜0.05).结论在此实验条件下,尚不能够认为TCDD对雌鼠血浆维生素A的水平有影响,但对维生素E的水平有一定影响.     

多环芳烃受体基因与细胞色素P4501A1/1B1基因表达的调控

目的 在体外人神经细胞瘤细胞株(SK-N-AS)中，以二恶英(TCDD)、三甲基胆蒽(3-MC)作为诱导化合物，探讨多环芳烃受体(AHR、ARNT)基因与细胞色素P4501A1／1B1(CYPlAl、CYPlBl)基因表达的调控，并研究其剂量反应关系和时间反应关系。方法 用常规的细胞培养方法，用二甲基亚砜(DMSO)、5．0、50．0、100．0nmol/L TCDD和0.1、1.0、10．0μmol/L 3-MC处理细胞12h、24h、48h、72h，利用提纯RNA和合成cDNA的药盒，合成cDNA，然后通过逆转录聚合跨反应(RT-PCR)表达AHR、ARNT和CYP1A1,CYP1B1基因，以β-actin作为内对照，分析不同处理剂量、时间时基因表达的强度。结果 4种基因在SK-N-AS中都有基本的表达，TCDD在50．0nmol/L以上，染毒处理48h、72h，对AHR、ARNT及CYPlAl基因表达都有上调作用；5．0nmol/L组在染毒处理72h后对AHR基因表达，50．0和100．0nmol/L组分别在染毒处理72h和48h时对CYPlBl基因表达也有上调作用；3-MCl．0、10.0umol/L在染毒72h后对AHR、ARNT、CYPlAl基因表达有上调作用，其中10．0μmol/L组在染毒48h后就有上调作用，但对CYPlBl基因表达上调仅仅在10．0μmol/L染毒48h组。结论 本研究结果提示，TCDD、3-MC两种多环芳烃类化合物在SK-N-AS中，在一定剂量和一定时间状态下对AHR、ARNT、CYPlAl及CYPlBl都有调控作用。     

二噁英对小鼠异位子宫内膜中IL-1β表达的影响

目的 探讨二噁英致子宫内膜异位症发病可能的作用机制.方法 ①60只小鼠建立子宫内膜异位症模型,分别给予二噁英(TCDD)灌胃染毒,每21天1次,于建模术后3、6、9周处死,鉴定异位病灶的形成,测量异位病灶面积;②按处死时间随机分为3周组、6周组、9周组,每组20只;每组再随机分成4个剂量组,分别是:对照组(给玉米油)、低剂量染毒组(1μg/kg TCDD)、中剂量染毒组(3μg/kg TCDD)和高剂量染毒组(10μg/kg TCDD);③采用半定量逆转录-聚合酶链反应检测不同染毒剂量组小鼠模型子宫内膜异位症异位病灶中白细胞介素-1β(IL-1β)mRNA的表达水平.结果 ①随TCDD染毒时间的延长和染毒剂量的增加,小鼠子宫内膜异位病灶面积相应增加,F值分别为107.349和171.408,均P<0.05;②小鼠子宫内膜异位病灶中白细胞介素-1β mRNA表达的上调,随TCDD染毒时间延长,F值分别为10.600、10.656和12.182,均P<0.05;随染毒剂量的增加,中剂量组和高剂量组F值分别为10.332和11.347,均P<0.05).结论 TCDD染毒促进了小鼠子宫内膜异位症模型异位病灶的发展,白细胞介素-1β表达上调可能是TCDD促异位病灶发展的作用机制之一.     

二噁英慢性低剂量暴露对雌性SD大鼠血清蛋白的影响

目的对慢性低剂量暴露于2,3,7,8-四氯二苯并二噁英(TCDD)的雌性SD大鼠血清蛋白改变进行研究,对TCDD毒性效应作进一步阐述。方法雌性SD大鼠随机分为3个染毒组和1个对照组[(n=8只/组,0 ng/(kg.d)、20 ng/(kg.d)、50 ng/(kg.d)、125 ng/(kg.d)],灌胃染毒29周,采用双向凝胶电泳和基质辅助激光解吸飞行时间串联质谱技术对大鼠血清进行蛋白组学研究,寻找差异蛋白点,并对其肝脏进行组织病理学检测。结果上调的蛋白包括补体C4,载脂蛋白A-Ⅳ前体和低分子量的激肽原前体;触珠蛋白和补体C3仅在染毒组大鼠凝胶中被识别,而对照组未见;而α-抑制因子Ⅲ前体只在对照组的胶上被识别。肝脏组织病理学检测显示染毒组大鼠肝脏出现肝细胞的脂肪变性、空泡形成、肝细胞坏死等改变,并且随染毒剂量的增加严重程度增加。结论慢性低剂量染毒使得血清蛋白谱发生改变,所改变的蛋白质与TCDD的免疫毒性、肝毒性、氧化应激等效应有关。血清差异蛋白可为TCDD毒作用分子标志物的筛选提供依据。     

亚慢性接触2,3,7,8-四氯二苯-并-二(口恶)英对成年雄性大鼠海马形态结构的影响

目的 研究亚慢性低剂量2,3,7,8-四氯二苯-并-二(口恶)英(2,3,7,8-tetrachlorodibenzo-p-dioxin,TCDD)染毒对SD雄性成年大鼠海马形态结构的影响.方法 将32只1月龄SPF级Sprague-Dawley雄性大鼠随机分为4组,分别为对照(玉米油)组和低(2 ng/kg)、中(1...     

Exposure to 3,3',4,4',5-pentachlorobiphenyl during embryonic development has a minimal effect on the cytochrome P4501A response to 2,3,7,8-tetrachlorodibenzo-p-dioxin in cultured chicken embryo hepatocytes

Concentrations of dioxin-like compounds in avian eggs can vary substantially between individuals, species, and collection sites. Although the inducibility of cytochrome P4501A (CYPIA) in hepatocyte cultures is commonly used to predict species sensitivity to environmental contaminants, it is not known how exposure to dioxin-like compounds during embryonic development might alter this biomarker response. To investigate this question, we injected vehicle or 0.4, 0.8, or 1.6 microg/kg of 3,3',4,4',5-pentachlorobiphenyl (PCB 126) into the air cell of fertilized chicken eggs before incubation, and we measured CYP1A endpoints in cultured hepatocytes of day-19 embryos from each treatment group. The CYP1A response to PCB 126 also was assessed in whole liver tissue. Embryonic exposure to the most environmentally relevant treatment, 0.4 microg/kg of PCB 126, increased CYPIA4 mRNA expression 29-fold compared to control values in whole liver tissue but only twofold compared to control values in cultured hepatocytes. The CYPIA response to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) was not altered in hepatocytes cultured from embryos treated with 0.4 microg/kg of PCB 126, but at 0.8 and 1.6 microg/kg of PCB 126, several concentration-dependent effects were observed. For example, embryos exposed to higher concentrations of PCB 126 in ovo were more responsive to CYP1A mRNA induction by TCDD in vitro. These findings suggest that exposure to environmental levels of dioxin-like compounds during incubation is not likely to alter species-sensitivity estimates derived from in vitro CYP1A data.     

烟焦油对小鼠肺多环芳烃受体和细胞色素P4501 A1基因mRNA水平的影响

目的研究烟焦油对小鼠肺多环芳烃化合物受体(AHR)、细胞色素P4501A1(CYP1A1)基因表达的影响.方法以5.29、10.58、15.87 mg/kg的烟焦油腹腔注射分别染毒小鼠,用提纯RNA试剂盒提取小鼠肺脏的RNA,用逆转录聚合酶链反应(RT-PCR)检测AHR和CYP1A1基因的表达,以β-actin作为内对照,分析不同处理剂量和不同处理时间后AHR和CYP1A1基因表达情况.结果以5.29 mg/kg烟焦油染毒小鼠72 h,AHR基因表达量的相对值为0.554±0.023,与吐温-80组(0.484±0.045)比较,差异有统计学意义(P＜0.05).以10.58、15.87 mg/kg的烟焦油染毒小鼠48和72 h,AHR基因表达量的相对值分别为0.555±0.014、0.606±0.051和0.566±0.014、0.684±0.069,分别与吐温-80组(0.486±0.060、0.484±0.045)比较,差异有统计学意义(P＜0.05或P＜0.01).CYP1A1基因表达量的相对值分别为1.535±0.021、1.643±0.046和1.624±0.056、1.739±0.038,分别与吐温-80组(1.436±0.016、1.404±0.036)比较,差异有统计学意义(P＜0.01).结论烟焦油在一定的浓度和时间内可使AHR和CYP1A1基因的表达增加,烟焦油对AHR基因表达的调控早于CYP1A1基因.     

Dose response for TCDD promotion of hepatocarcinogenesis in rats initiated with DEN: histologic, biochemical, and cell proliferation endpoints.

The present study examines the dose-response relationship for 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) promotion of histologic and biochemical parameters by using a two-stage model for hepatocarcinogenesis in female Sprague-Dawley rats initiated with a single intraperitoneal dose of 175 mg of diethylnitrosamine (DEN)/kg body weight at 70 days of age. Starting 2 weeks after initiation, treatment groups of 8-10 rats were given TCDD by gavage in corn oil once every 2 weeks for 30 weeks. Doses were 3.5, 10.7, 35.7, and 125 ng TCDD/kg body weight/day. A significant body weight reduction was present in the noninitiated group that received 125 ng TCDD. Relative liver weight was statistically increased in initiated rats treated with > or = 10.7 ng TCDD and in noninitiated rats treated with > or = 35.7 ng TCDD. Histopathologic evidence of cytotoxicity was dose-related in all TCDD-treated groups. There was a statistically significant dose response in the bromodeoxyuridine (BrdU) S-phase labeling index (LI) in the DEN-initiated rats (p < 0.01) and a marginally significant trend in the saline-treated rats (p = 0.10), but proliferating cell nuclear antigen S-phase LI and growth fraction within altered hepatic foci showed no increase. Among the DEN-initiated groups there was a significant increase in glutathione S-transferase altered hepatic foci stereological parameters in the 125 ng TCDD group. This study demonstrates that dose-response relationships for TCDD's effects on cell proliferation growth of altered hepatic foci are different from previously reported effects on P450 gene expression, indicating that different biological or biochemical responses may exhibit different dose-response relationships.(ABSTRACT TRUNCATED AT 250 WORDS)     

二(噁)英对星形胶质细胞和神经母细胞瘤细胞线粒体的影响

目的 探讨2,3,7,8-四氯二苯并二(噁)英(TCDD)的神经毒性.方法 选择人星形胶质细胞和人神经母细胞瘤细胞(SH-SY5Y),4个染毒组和对照组分别暴露于1、10、50、100 nmol/L TCDD和二甲基亚砜(DMSO)24 h.用透射电镜观察细胞线粒体超微结构,用RT-PCR检测细胞的线粒体相关基因mRNA表达水平.结果 透射电镜观察到TCDD染毒组细胞线粒体嵴数目减少,出现空泡化.RT-PCR结果显示,与对照组相比,染毒组两种细胞HSPD1、MFN1、MFN2、SLC25A10mRNA的表达水平下降,TSPO和SLC25A 27 mRNA的表达水平升高,差异均有统计学意义(P＜0.05).结论 TCDD对星形胶质细胞和SH-SY5Y细胞具有损伤作用,可以影响神经细胞线粒体的正常形态、正常转运功能和动力学过程.     

Evaluation of Placentation and the Role of the Aryl Hydrocarbon Receptor Pathway in a Rat Model of Dioxin Exposure

Background: Our environment is replete with chemicals that can affect embryonic and extraembryonic development. Dioxins, such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), are compounds affecting development through the aryl hydrocarbon receptor (AHR).Objectives: The purpose of this investigation was to examine the effects of TCDD exposure on pregnancy and placentation and to evaluate roles for AHR and cytochrome P450 1A1 (CYP1A1) in TCDD action.Methods: Actions of TCDD were examined in wild-type and genome-edited rat models. Placenta phenotyping was assessed using morphological, biochemical, and molecular analyses.Results: TCDD exposures were shown to result in placental adaptations and at higher doses, pregnancy termination. Deep intrauterine endovascular trophoblast cell invasion was a prominent placentation site adaptation to TCDD. TCDD-mediated placental adaptations were dependent upon maternal AHR signaling but not upon placental or fetal AHR signaling nor the presence of a prominent AHR target, CYP1A1. At the placentation site, TCDD activated AHR signaling within endothelial cells but not trophoblast cells. Immune and trophoblast cell behaviors at the uterine–placental interface were guided by the actions of TCDD on endothelial cells.Discussion: We identified an AHR regulatory pathway in rats activated by dioxin affecting uterine and trophoblast cell dynamics and the formation of the hemochorial placenta. https://doi.org/10.1289/EHP9256     

CYP2E1在大蒜油拮抗正己烷神经损伤中的作用

目的 研究CYP2E1在大蒜油(garlic oil,GO)阻止正己烷(n-hexane)致大鼠周围神经损伤的作用及其机制.方法 雄性Wistar大鼠50只,随机分为正常对照组、GO对照组、正己烷模型组、GO低剂量加正己烷组和高剂量加正己烷组(n=10).模型组及GO低、高剂量组大鼠分别给予2000 mg/kg正己烷灌胃;GO低、高剂量组大鼠在正己烷灌胃前1h分别给予40、80 mg/kg GO灌胃,GO对照组给予80 mg/kg,每周6次,持续10周.每2周测步态评分,监测大鼠周围神经损伤情况.于第10周末,断头处死大鼠,检测肝组织中CYP2E1表达及活力的改变,以及血清中2,5-己二酮(2,5-HD)含量的变化.结果 与正常对照组相比,GO对照组大鼠肝脏中CYP2E1含量及活力分别下降83.1％和48.3％,且差异均有统计学意义(P＜0.01);与正常对照组相比,模型组大鼠肝脏中CYP2E1含量及活力分别升高122.5％和72.2％,且差异均有统计学意义(P＜0.01);与模型组相比,GO低、高剂量组大鼠肝脏中CYP2E1含量分别降低32.9％和39.1％,且CYP2E1活力分别降低27.4％和44.5％,差异均有统计学意义(P＜0.01);与模型组相比,GO低、高剂量组大鼠血清中2,5-HD含量分别下降47.7％和78.7％,且差异均有统计学意义(P＜0.01).各组步态评分显示,模型组及GO低、高剂量组均明显高于对照组,但GO低、高剂量组低于模型组,差异有统计学意义(P＜0.05).结论 GO能够有效拮抗正己烷的外周神经损伤,其机制可能与肝脏中CYP2E1含量及活力降低,使正己烷代谢为2,5-HD减少有关.     

人参低聚肽对急性酒精性肝损伤大鼠的保护作用

目的 探讨人参低聚肽（GOP）对酒精诱导的大鼠急性肝损伤的保护作用及其可能机制。方法 采用SPF级SD雄性大鼠,随机分为7组,每组10只,包括,1个空白对照组、1个模型对照组、1个乳清蛋白对照组（0.250 0 g/kg）和4个GOP剂量组(0.062 5、0.125 0、0.250 0、0.500 0 g/kg)。连续灌胃30d后,采用体积分数 50%的酒精以 7g/(kg·BW)剂量灌胃造成大鼠急性酒精性肝损伤模型,测定大鼠血清ALT、AST活性和肝脏SOD、GSH、GSH-PX及MDA含量。结果 与模型对照组相比,GOP干预可以显著降低大鼠血清ALT、AST和肝组织MDA(P<0.05或P<0.01)的水平,增加肝组织SOD 、GSH和GSH-PX的活性（P<0.05或P<0.01)。结论 GOP对酒精诱导引起的大鼠急性肝损伤具有保护作用,其机制可能与提高机体抗氧化水平有关。     

Effects of Dietary Exposure to 2,3,7,8-Tetrachlorodibenzo-p-dioxin in Adult Female Mink (Mustela vison)

Adult female mink were fed diets supplemented with 0, 0.001, 0.01, 0.1, 1, 10, or 100 ppb 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) for up to 125 days. There was a dose-dependent decrease in feed consumption and body weights indicative of the “wasting syndrome” previously reported for mink and other species exposed to chlorinated hydrocarbon compounds. Mortality reached 12.5, 62.5, and 100% by day 28 in the 1-, 10-, and 100-ppb groups, respectively, and by day 125, mortality increased to 62.5 and 100% in the 1- and 10-ppb groups, respectively. Adrenal gland weights were significantly greater in the three highest dose groups compared to the control group. The percentage of band neutrophils was also significantly greater in the TCDD-treated groups compared to the control. LC₅₀ (±SE) values for 28 and 125 days of dietary exposure to TCDD were calculated to be 4.8 ± 4.99 ppb and 0.85 ± 0.64 ppb, respectively. Based on feed consumption of control mink, these LC₅₀ concentrations approximate 0.264 and 0.047 μg TCDD/kg body weight/day for the 28- and 125-day exposure periods, respectively. These results confirm the sensitivity of mink to TCDD. Received: 4 August 1997/Accepted: 5 February 1998     

Flow cytometric analysis of lymphocyte subpopulations in the spleen and thymus of mice exposed to an acute immunosuppressive dose of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)

The objective of the present studies was to determine if acute exposure to an immunotoxic dose of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) produces alterations in the expression of lymphocyte surface markers as measured by multiparameter flow cytometry. The immunotoxicity of a single oral dose of TCDD was assessed by the anti-SRBC PFC response; an ED50 of 0.74 micrograms/kg was determined. Subpopulations in the spleen and thymus of C57B1/6 mice were analyzed 2 days following exposure to 2 micrograms/kg TCDD. In addition, splenic lymphocyte subsets were examined on Days 1-4 following SRBC challenge of mice treated with 0, 2, or 5 micrograms/kg TCDD. T and B cells were identified by single parameter analysis of Thy 1.2 and Ig expression. T cell subsets were defined by dual parameter analysis of CD4 and CD8 expression. In TCDD-treated mice, the percentage and the total number of double-positive CD4+ CD8+ thymocytes were significantly decreased while the percentage but not the total number of double-negative CD4- CD8- thymocytes was significantly increased. No changes in the percentage or total number of single positive (CD4+ CD8- or CD4- CD8+) thymocyte subsets were observed. In contrast to the thymus, lymphocyte subsets in the spleen were not significantly altered in percentage or total number 2 days following acute TCDD exposure. When splenic lymphocytes were analyzed daily following SRBC challenge, Ig+, Thy 1.2+, and CD4+ CD8- subpopulations remained relatively unchanged in both control and TCDD-treated animals. A small but significant decrease in the percentage of CD4- CD8+ T cells was observed on Day 3 in mice treated with 2 or 5 micrograms/kg TCDD when compared to that of vehicle-treated mice. The total number of CD4- CD8+ splenocytes was also significantly lower in the 5-micrograms/kg group on Day 3. However, this effect appeared to result from an elevation of the CD4- CD8+ subset in the controls rather than from a reduction in the TCDD-treated groups. Double-positive (CD4+ CD8+) lymphocytes were not detected in either control or TCDD-treated spleens. These results indicate that an acute dose of TCDD which reduced the splenic anti-SRBC response by 65-80% did not cause detectable changes in major splenic lymphocyte subpopulations. This is an important finding from the standpoint of utilizing lymphocyte subset analysis to screen for potential immunotoxic effects of TCDD. Specifically, the absence of subset changes does not preclude the presence of functional immunosuppression.