Graduate Program of Toxicology, Department of Soil Science, and Toxicology Group, University of Saskatchewan, Saskatoon, SK, S7N 5A8.
Environ Sci Technol. 2009 Nov 15;43(22):8652-7. doi: 10.1021/es900837y.
In vitro gastrointestinal models, used to measure the metal(loid) bioaccessibility for site specific risk assessment, are typically operated under fasted conditions. We evaluated the hypothesis that fed conditions increase arsenic bioaccessibility on three reference soils (NIST 2711, NIST 2709, and BGS 102) and the bulk and <38 mum size fractions of a mine tailing. The three nutritional states included a fed state with a carbohydrate mixture, a second fed state with homogenized crowberries (Empetrum nigrum), and a fasted state. The carbohydrate mixture increased arsenic bioaccessibility from four of five samples in the simulator of the human intestinal microbial ecosystem (SHIME) stomach but only three of five samples in the SHIME small intestine and colon. In contrast, crowberries increased arsenic bioaccessibility from four of five samples in the SHIME small intestine but had variable affects in the SHIME stomach and colon. The effect of nutritional status on arsenic bioaccessibility was potentially mediated via ligand-promoted dissolution in the SHIME stomach and small intestine. The displacement of arsenic with phosphate was potentially present in the SHIME small intestine but not the SHIME stomach. Microbial activity increased arsenic bioaccessibility relative to sterile conditions from four of five samples under fasted conditions and three of the five samples under fed conditions, which may suggest that in vitro gastrointestinal (GI) models operated under fed conditions and with microbes provide a more conservative estimate of in vitro bioaccessibility. However, for some samples, the arsenic bioaccessibility in the SHIME colon (with microbial activity) was equivalent to values observed in a separate physiologically based extraction test under small intestinal conditions (without microbial activity). These results suggest that the incorporation of microbial activity into in vitro GI models does not necessarily make estimates of arsenic bioaccessibility more protective than those generated using in vitro models that do not include microbial activity.
在用于进行特定部位风险评估的金属（类）生物可给性测量的体外胃肠道模型中，通常在空腹条件下运行。我们评估了这样一个假设，即在三种参考土壤（NIST 2711、NIST 2709 和 BGS 102）和尾矿的大块和<38 微米粒径部分，在进食条件下会增加砷的生物可给性。三种营养状态包括：一种是碳水化合物混合物喂养状态，另一种是用均匀化的越桔（Empetrum nigrum）喂养的状态，还有一种是空腹状态。碳水化合物混合物增加了模拟人类肠道微生物生态系统（SHIME）胃中的五种样本中的四种砷的生物可给性，但在 SHIME 小肠和结肠中仅增加了五种样本中的三种。相比之下，越桔在 SHIME 小肠中增加了五种样本中的四种砷的生物可给性，但在 SHIME 胃和结肠中的影响则不同。营养状态对砷生物可给性的影响可能是通过在 SHIME 胃和小肠中配体促进溶解来介导的。在 SHIME 小肠中可能存在砷与磷酸盐的置换，但在 SHIME 胃中则没有。在禁食条件下，微生物活性使四种样本中的砷生物可给性相对于无菌条件下增加，而在进食条件下则使五种样本中的三种增加，这可能表明，在进食条件下且含有微生物的体外胃肠道（GI）模型提供了更保守的体外生物可给性估计。然而，对于一些样本，在 SHIME 结肠（含微生物活性）中观察到的砷生物可给性与在另一个单独的生理相关提取测试中小肠条件（不含微生物活性）下观察到的值相当。这些结果表明，将微生物活性纳入体外 GI 模型不一定会使砷生物可给性的估计值比不包括微生物活性的体外模型生成的值更具保护性。
