Vasiluk Luba, Pinto Linda J, Walji Zahra A, Tsang Wing Shan, Gobas Frank A P C, Eickhoff Curtis, Moore Margo M
Department of Biological Sciences, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada.
Environ Toxicol Chem. 2007 Mar;26(3):387-93. doi: 10.1897/06-343r.1.
A major route of exposure to hydrophobic organic contaminants (HOCs), such as benzo[a]pyrene (BaP), is ingestion. Matrix-bound HOCs may become bioavailable after mobilization by the gastrointestinal fluids followed by sorption to the intestinal epithelium. The purpose of this research was to measure the bioavailability of [14C]-BaP bound to pristine soils or field-contaminated sediment using an in vitro model of gastrointestinal digestion followed by sorption to human enterocytes (Caco-2 cells) or to a surrogate membrane, ethylene vinyl acetate (EVA) thin film. Although Caco-2 cells had a twofold higher lipid-normalized fugacity capacity than EVA, [14C]-BaP uptake by Caco-2 lipids and EVA thin film demonstrated a linear relationship within the range of BaP concentrations tested. These results suggest that EVA thin film is a good membrane surrogate for passive uptake of BaP. The in vitro system provided enough sensitivity to detect matrix effects on bioavailability; after 5 h, significantly lower concentrations of [14C]-BaP were sorbed into Caco-2 cells from soil containing a higher percentage of organic matter compared to soil with a lower percentage of organic matter. The [14C]-BaP desorption rate from Caco-2 lipids consistently was twofold higher than from EVA thin film for all matrices tested. The more rapid kinetics observed with Caco-2 cells probably were due to the greater surface area available for absorption/desorption in the cells. After 5 h, the uptake of BaP into Caco-2 lipid was similar in live and metabolically inert Caco-2 cells, suggesting that the primary route of BaP uptake is by passive diffusion. Moreover, the driving force for uptake is the fugacity gradient that exists between the gastrointestinal fluid and the membrane.
接触疏水性有机污染物（HOCs）（如苯并[a]芘（BaP））的主要途径是摄入。与基质结合的HOCs在被胃肠液溶解并吸附到肠上皮细胞后可能会变得具有生物可利用性。本研究的目的是使用胃肠消化的体外模型，然后将其吸附到人肠上皮细胞（Caco-2细胞）或替代膜乙烯醋酸乙烯酯（EVA）薄膜上，来测量与原始土壤或现场污染沉积物结合的[14C]-BaP的生物可利用性。尽管Caco-2细胞的脂质标准化逸度容量比EVA高两倍，但在测试的BaP浓度范围内，Caco-2脂质和EVA薄膜对[14C]-BaP的摄取呈现线性关系。这些结果表明，EVA薄膜是BaP被动摄取的良好膜替代物。体外系统具有足够的灵敏度来检测基质对生物可利用性的影响；5小时后，与有机质含量较低的土壤相比，从有机质含量较高的土壤中吸附到Caco-2细胞中的[14C]-BaP浓度显著降低。对于所有测试的基质，[14C]-BaP从Caco-2脂质中的解吸速率始终比从EVA薄膜中的解吸速率高两倍。在Caco-2细胞中观察到的更快动力学可能是由于细胞中可用于吸收/解吸的表面积更大。5小时后，活的和代谢惰性的Caco-2细胞对BaP进入Caco-2脂质的摄取相似，这表明BaP摄取的主要途径是被动扩散。此外，摄取的驱动力是胃肠液和膜之间存在的逸度梯度。
