Sallee V L, Wilson F A, Dietschy J M
J Lipid Res. 1972 Mar;13(2):184-92.
An in vitro method is presented which measures valid, unidirectional uptake rates for lipids across the intestinal brush border. This method combines analysis by a newly devised, double isotope counting system for solubilized tissue with the use of a nonabsorbable marker to correct gross uptake determinations for contamination by adherent mucosal fluid. Of seven markers, only [(3)H]inulin measured adherent mucosal fluid volumes as much as 20% greater than the other markers. Diffusion of the nonabsorbable marker, as well as of the compound being studied, into the unstirred layer made the time course of uptake critically important. The time lag for diffusion of marker invalidates the use of 1-min incubation periods; however, a linear time course of uptake that intercepts essentially at zero was found for taurocholate and octanoate for periods of from 2 to 5 min. Working within this critical time period with jejunum, it was shown that tissue dry weight was an appropriate measure of the amount of tissue and that uptake rates for taurocholic, octanoic, and lauric acids were linear with respect to concentration. Tissue binding of compounds was not significant. The results demonstrate that careful use of the described method yields accurate measurement of unidirectional uptake rates of lipids across the brush border that are of critical importance in defining the characteristics of membrane penetration and the rate-limiting steps in fat and sterol absorption.
本文介绍了一种体外方法，该方法可测量脂质跨肠刷状缘的有效单向摄取率。此方法将新设计的双同位素计数系统对溶解组织的分析与使用不可吸收标记物相结合，以校正因粘附粘膜液污染而导致的总摄取量测定结果。在七种标记物中，只有[³H]菊粉测量的粘附粘膜液体积比其他标记物大20%。不可吸收标记物以及所研究化合物向未搅拌层的扩散使得摄取的时间进程至关重要。标记物扩散的时间滞后使得1分钟孵育期的使用无效；然而，对于牛磺胆酸盐和辛酸，在2至5分钟的时间段内发现摄取的时间进程呈线性，且基本上在零处相交。在空肠的这个关键时间段内进行研究，结果表明组织干重是组织量的合适度量，并且牛磺胆酸、辛酸和月桂酸的摄取率与浓度呈线性关系。化合物的组织结合并不显著。结果表明，谨慎使用所描述的方法可准确测量脂质跨刷状缘的单向摄取率，这对于定义膜渗透特性以及脂肪和固醇吸收中的限速步骤至关重要。
