Department of Crop and Soil Sciences, Michigan State University, East Lansing, Michigan, USA.
Environ Toxicol Chem. 2011 Dec;30(12):2748-55. doi: 10.1002/etc.701.
2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a highly toxic environmental contaminant found in soils and sediments. Because of its exceptionally low water solubility, this compound exists predominantly in the sorbed state in natural environments. Clay minerals, especially expandable smectite clays, are one of the major component geosorbents in soils and sediments that can function as an effective adsorbent for environmental dioxins, including TCDD. In this study, TCDD was intercalated in the smectite clay saponite by an incipient wetness method. The primary goal of this study was to intercalate TCDD in natural K-saponite clay and evaluate its immunotoxic effects in vivo. The relative bioavailability of TCDD was evaluated by comparing the metabolic activity of TCDD administered in the adsorbed state as an intercalate in saponite and freely dissolved in corn oil. This comparison revealed nearly identical TCDD-induced suppression of humoral immunity, a well-established and sensitive sequela, in a mammalian (mouse) model. This result suggests that TCDD adsorbed by clays is likely to be available for biouptake and biodistribution in mammals, consistent with previous observations of TCDD in livestock exposed to dioxin-contaminated ball clays that were used as feed additives. Adsorption of TCDD by clay minerals does not appear to mitigate risk associated with TCDD exposure substantially.
2,3,7,8-四氯二苯并对二恶英(TCDD)是一种存在于土壤和沉积物中的高毒性环境污染物。由于其极低的水溶性,这种化合物主要以吸附状态存在于自然环境中。粘土矿物,特别是可膨胀的蒙脱石粘土,是土壤和沉积物中主要的成分之一,是环境中二恶英(包括 TCDD)的有效吸附剂。在这项研究中,TCDD 通过初始湿化学法插入到蒙脱石粘土皂石中。本研究的主要目的是将 TCDD 插入天然 K-皂石粘土中,并评估其体内的免疫毒性作用。通过比较以吸附状态作为皂石中的插层体和自由溶解在玉米油中的 TCDD 给药,评估 TCDD 的相对生物利用度。这种比较揭示了在哺乳动物(小鼠)模型中,TCDD 诱导的体液免疫抑制作用几乎完全相同,这是一种已确立且敏感的后果。这一结果表明,粘土吸附的 TCDD 可能会被生物吸收和在哺乳动物体内分布,这与先前在接触受二恶英污染的球粘土作为饲料添加剂的牲畜中观察到的 TCDD 一致。粘土矿物对 TCDD 的吸附似乎没有显著减轻与 TCDD 暴露相关的风险。