Evaluation of dioxins contamination to the large field mouse, Apodemus speciosus

多氯二苯并-对二恶英(PCDDs)、多氯二苯并呋喃(PCDFs)和类二恶英多氯二苯并呋喃(Dioxine-like PCbs)，统称为二恶英，是一种剧毒、持久的亲脂性物质。这些化合物主要是在工业废物焚烧或在填埋后的土地上燃烧产生的，然后释放到土壤和空气中。众所周知，这些物质会在食物链上进行生物积累，并对食物链中较高消费者的生殖活动造成损害。然而，最近有报道称，在包括狐狸和黄鼠狼等消费水平较高的食物网络中，被视为消费水平相对较低的日本大田鼠是哺乳动物中二恶英积累量最高的物种，这意味着该物种成为评估二恶英污染对野生动物影响的有效生物标志物。二恶英引起多种生物和毒素…更常见的反应，在实验动物中表现为畸形、胸腺萎缩、严重的上皮性疾病、消瘦症状、肿瘤促进和药物代谢酶的诱导。此外，二恶英所表现出的激素行为会扰乱动物的内分泌系统，从而导致性腺异常和精子数量减少。为了阐明二恶英对野生种群的生理和生态影响，我们首先研究了土壤中二恶英浓度与其在小鼠肝脏中的积累水平之间的关系，以及二恶英在小鼠体内的积累与成年雄性大鼠精子活动或精子数量的关系。接下来，我们分析了广为人知的2，3，7，8-四氯二苯并-对-二恶英(TCDD)受体-大灵芝的芳香烃受体(AhR)的多态性及其功能差异。从七个点收集了老鼠和土壤；新泻县四个点，山形县一个点，崎玉县一个点，福冈县一个点。土壤中的二恶英浓度与小鼠体内的二恶英积累量之间没有明显的相关性，尽管小鼠的二恶英积累量随着土壤中的二恶英浓度的增加而增加。另一方面，除了二恶英污染最高的研究地点外，精子活力和精子数量都随着二恶英的积累而下降。A orosus AhR的一级结构变异极大。突变集中在两个区域，即Pas-A和Pas-B之间和反式激活区域。在对3mc的反应中，特殊拟南芥AhR具有较高的转录活性。一个Q799突变为R的反式激活结构域降低了活性。Pas结构域不同突变间转录活性无明显差异。因此，二恶英可能会扰乱种内分泌系统，种内变异较大的AhR可能成为在种群水平上评价二恶英作用的有效分子标记。较少

Polychlorinated dibezo-p-dioxins (PCDDs), polychrorinated dibenzofurans (PCDFs) and dioxin-like poly chrorinated dibenzofurans (dioxine-like PCBs), which are generically called as dioxins, are highly toxic and persistent lipophilic substances. These compounds are mainly produced in the process of incineration for industrial waste products or burning on the filled-up land for such products, and then are released into soil and air. These are known to bioaccumulate up the food chain and damage to reproductive activities of higher consumers in food web. Recently, however, it have been reported that the Japanese large field mouse, Apodemus speciosus, which have been regarded as comparatively lower consumer, had the highest accumulation of dioxins among mammals in a food web including higher consumers such as fox and weasel, which means that this species become an effective biomarker for evaluating an effect of dioxins contamination to wildlives. Dioxins cause various biological and toxicolo … More gical responses, typified by teratogenesis, thymic atrophy, severe epithelial disorders, wasting symdrome, tumore promotion, and induction of drug-metabolizing enzymes in experimental animals. Furthermore, the hormonal acts that dioxins exhibit make the endocrine system of animals disrupt and consequently cause abnormal sexual gland and decreased sperm counts.To clarify physiological and ecological effects of dioxins exposure on wild populations of A.speciosus, we firstly investigated the relationship between dioxins concentration in soil and its accumulation level in mouse liver, and the relationships between dioxins accumulation in mouse and sperm activity, or sperm counts, in adult male A.speciosus. Next, we analyzed polymorphism and its functional difference in aryl hydrocarbon receptor (AhR) of A.speciosus, which is well known as the receptor of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Mice and soils were collected from seven points ; four points in Niigata prefecture, one in Yamagata prefecture, one in Saitama prefecture, and one in Fukuoka prefecture. No significant correlation found between concentrations of dioxins in soils and dioxin accumulation levels in mice, although dioxin accumulations in mice tended to increase with dioxin concentrations in soils. On the other hand, the sperm activity and sperm count were decreased with dioxin accumulation, in the case except for the highest study site of dioxin contamination. Primary structure of A speciosus AhR was extremely variable. The mutations were concentrated in two regions, i.e. between PAS-A and PAS-B, and transactivation domain. A.speciosus AhR showed high transcriptional activity in response to 3MC. One mutation of Q799 to R in transactivation domain decreased activity. On the other hand, there was no difference in transcriptional activity among mutations in PAS domain.In conclusion, dioxins may disrupt the endocrine system of A.speciosus and AhR having high intraspecific variation may become an effective molecular marker to evaluate effect of dioxins at population level. Less