Van Itallie Christina M, Anderson James M
Methods Mol Biol. 2011;762:1-11. doi: 10.1007/978-1-61779-185-7_1.
Tight junctions restrict the paracellular movement of ions, solutes, drugs, and larger material across epithelia and endothelia. For practical purposes, the barrier can be modeled as having two components. The first is a system of small 4 Å radius pores lined or created by claudins. The pores show variable ionic charge selectivity and electrical resistance based on the pattern of claudin proteins expressed in a particular junction. Transport of compounds that are larger than 4 Å are not subject to discrimination based on size or charge; they are likely passing through transient breaks in the tight junction barrier. The magnitude of the first and second pathways varies among epithelia and is altered in response to physiological and pathological stimuli. Unfortunately, most studies of permeability use few tracer sizes and thus provide limited information on size-dependent changes in permeability. Here we describe a method for simultaneously measuring the size-dependence of apparent permeability using a continuous series of polyethylene polymers which allows quantification of both the pore and leak pathways.
紧密连接限制离子、溶质、药物及更大物质通过上皮细胞和内皮细胞的细胞旁移动。实际上，这种屏障可被模拟为具有两个组成部分。第一个是由紧密连接蛋白排列或形成的半径为4 Å的小孔系统。这些小孔基于在特定连接中表达的紧密连接蛋白模式表现出可变的离子电荷选择性和电阻。大于4 Å的化合物的转运不受基于大小或电荷的歧视；它们可能是通过紧密连接屏障中的瞬时间隙通过的。第一和第二途径的大小在上皮细胞之间有所不同，并会因生理和病理刺激而改变。不幸的是，大多数通透性研究使用的示踪剂大小很少，因此提供的关于通透性大小依赖性变化的信息有限。在此，我们描述了一种使用一系列连续的聚乙烯聚合物同时测量表观通透性大小依赖性的方法，该方法能够对孔道和渗漏途径进行量化。
