Saito H, Inui K
Department of Hospital Pharmacy, School of Medicine, Tokyo Medical and Dental University, Japan.
Am J Physiol. 1993 Aug;265(2 Pt 1):G289-94. doi: 10.1152/ajpgi.1993.265.2.G289.
The localization and transport characteristics of dipeptide transporters of the intestinal epithelial cell line Caco-2 were examined by measuring the intracellular accumulation and transcellular flux of Bestatin, a dipeptide-like anticancer agent. When added to the apical surface of Caco-2 monolayers grown on microporous membrane filters, Bestatin was accumulated in the cells and was transported unidirectionally to the basolateral side. The cellular uptake of Bestatin from the basolateral as well as from the apical surface was inhibited by excess dipeptides. Bestatin accumulation from the apical surface was dependent on the pH of the incubation medium with an optimal pH of 6.0, whereas uptake from the basolateral surface was insensitive to the medium pH. Kinetic parameters for Bestatin uptake also indicated that the basolateral and apical dipeptide transporters could be distinguished from each other. A sulfhydryl reagent, p-chloromercuribenzene sulfonate, inhibited Bestatin accumulation from both surfaces, although the inhibitory effect on the basolateral transport was greater than that on the apical transport. These findings suggest not only that dipeptide transporters exist on both the apical and basolateral membranes of Caco-2 cells but also that the basolateral dipeptide transporter is distinct from the apical H(+)-dipeptide cotransporter.
通过测量二肽样抗癌剂贝司他汀（Bestatin）在细胞内的积累和跨细胞通量，研究了肠上皮细胞系Caco-2中二肽转运体的定位和转运特性。当将贝司他汀添加到生长在微孔膜滤器上的Caco-2单层细胞的顶端表面时，它会在细胞内积累，并单向转运至基底外侧。过量的二肽会抑制贝司他汀从基底外侧以及顶端表面的细胞摄取。从顶端表面摄取贝司他汀取决于孵育培养基的pH值，最佳pH值为6.0，而从基底外侧表面摄取则对培养基pH值不敏感。贝司他汀摄取的动力学参数也表明，基底外侧和顶端二肽转运体可以相互区分。一种巯基试剂对氯汞苯磺酸盐会抑制贝司他汀从两个表面的积累，尽管对基底外侧转运的抑制作用大于对顶端转运的抑制作用。这些发现不仅表明Caco-2细胞的顶端和基底外侧膜上都存在二肽转运体，而且基底外侧二肽转运体与顶端H(+)-二肽共转运体不同。
