Smith Jordan Ned, Carver Zana A, Weber Thomas J, Timchalk Charles
Health Impacts and Exposure Science, Pacific Northwest National Laboratory (PNNL), Richland, Washington, USA.
Toxicol Sci. 2017 Jun 1;157(2):438-450. doi: 10.1093/toxsci/kfx055.
A combination experimental and computational approach was developed to predict chemical transport into saliva. A serous-acinar chemical transport assay was established to measure chemical transport with nonphysiological (standard cell culture medium) and physiological (using surrogate plasma and saliva medium) conditions using 3,5,6-trichloro-2-pyridinol (TCPy) a metabolite of the pesticide chlorpyrifos. High levels of TCPy protein binding were observed in cell culture medium and rat plasma resulting in different TCPy transport behaviors in the 2 experimental conditions. In the nonphysiological transport experiment, TCPy reached equilibrium at equivalent concentrations in apical and basolateral chambers. At higher TCPy doses, increased unbound TCPy was observed, and TCPy concentrations in apical and basolateral chambers reached equilibrium faster than lower doses, suggesting only unbound TCPy is able to cross the cellular monolayer. In the physiological experiment, TCPy transport was slower than nonphysiological conditions, and equilibrium was achieved at different concentrations in apical and basolateral chambers at a comparable ratio (0.034) to what was previously measured in rats dosed with TCPy (saliva:blood ratio: 0.049). A cellular transport computational model was developed based on TCPy protein binding kinetics and simulated all transport experiments reasonably well using different permeability coefficients for the 2 experimental conditions (1.14 vs 0.4 cm/h for nonphysiological and physiological experiments, respectively). The computational model was integrated into a physiologically based pharmacokinetic model and accurately predicted TCPy concentrations in saliva of rats dosed with TCPy. Overall, this study demonstrates an approach to predict chemical transport in saliva, potentially increasing the utility of salivary biomonitoring in the future.
开发了一种实验与计算相结合的方法来预测化学物质向唾液中的转运。建立了一种浆液性腺泡化学物质转运测定法，以测量在非生理条件（标准细胞培养基）和生理条件（使用替代血浆和唾液培养基）下使用农药毒死蜱的代谢物3,5,6 - 三氯 - 2 - 吡啶醇（TCPy）的化学物质转运。在细胞培养基和大鼠血浆中观察到高水平的TCPy蛋白结合，导致在两种实验条件下TCPy的转运行为不同。在非生理转运实验中，TCPy在顶侧和基底外侧腔室中达到等效浓度的平衡。在较高的TCPy剂量下，观察到未结合的TCPy增加，并且顶侧和基底外侧腔室中的TCPy浓度比较低剂量时更快达到平衡，表明只有未结合的TCPy能够穿过细胞单层。在生理实验中，TCPy的转运比非生理条件下慢，并且在顶侧和基底外侧腔室中以与先前在给予TCPy的大鼠中测量的相当的比例（0.034）在不同浓度下达到平衡（唾液：血液比例：0.049）。基于TCPy蛋白结合动力学开发了一种细胞转运计算模型，并使用两种实验条件下不同的渗透系数（非生理和生理实验分别为1.14和0.4 cm/h）对所有转运实验进行了合理的模拟。该计算模型被整合到基于生理学的药代动力学模型中，并准确预测了给予TCPy的大鼠唾液中TCPy的浓度。总体而言，本研究展示了一种预测唾液中化学物质转运的方法，可能会增加未来唾液生物监测的实用性。
