Agu Remigius, Dang Hoang Vu, Jorissen Mark, Willems Tom, Vandoninck Sandy, Van Lint Johan, Vandenheede Jackie V, Kinget Renaat, Verbeke Norbert
Laboratory for Pharmacotechnology and Biopharmacy, K.U. Leuven, Campus Gasthuisberg O&N, Herestraat 49, B-3000 Leuven, Belgium.
Pharm Res. 2003 Aug;20(8):1125-32. doi: 10.1023/a:1025028410131.
The purpose of this study was to provide functional and molecular evidence to support the existence of large neutral amino acid transporters in human nasal epithelium using nasal primary cell culture model.
L-Phenylalanine was used as a model substrate to characterize carrier-mediated permeation of amino acids across human nasal epithelium. The influence of temperature, concentration, other amino acids, metabolic/transport inhibitors, and polarity/stereo-selectivity on transport of the model compound was investigated. Reverse transcriptase polymerase chain reaction was used for molecular characterization of the existence of the transporters.
The transport of L-phenylalanine across the human nasal epithelium was polarized (apical --> basolateral >> basolateral --> apical), saturable (Km = 1.23 mM; Vmax = 805.1 nmol/mg protein/min) and stereo-selective (permeation of L-phenylalanine >> D-Phenylalanine). Its permeation was significantly (< 0.05) reduced by cationic, small and large neutral amino acids, oubain, amiloride, sodium-free medium, and temperature lowering. Reverse transcriptase polymerase chain reaction revealed the presence of the broad-scope cationic-dependent amino acid transporter gene (y+LAT-2) in the human nasal epithelium.
Based on the results of this study, one may postulate that the human nasal epithelium expresses L-amino acid transporters. More studies are necessary for detailed characterization of the transporters.
本研究旨在利用鼻原代细胞培养模型，提供功能和分子证据，以支持人鼻上皮中存在大中性氨基酸转运体。
以L-苯丙氨酸作为模型底物，表征氨基酸通过人鼻上皮的载体介导转运。研究了温度、浓度、其他氨基酸、代谢/转运抑制剂以及极性/立体选择性对模型化合物转运的影响。采用逆转录聚合酶链反应对转运体的存在进行分子表征。
L-苯丙氨酸通过人鼻上皮的转运具有极性（从顶端到基底外侧>>从基底外侧到顶端）、可饱和性（Km = 1.23 mM；Vmax = 805.1 nmol/mg蛋白质/分钟）和立体选择性（L-苯丙氨酸的转运>>D-苯丙氨酸）。阳离子、小和大中性氨基酸、哇巴因、氨氯地平、无钠培养基和降温可使其转运显著降低（<0.05）。逆转录聚合酶链反应显示人鼻上皮中存在广泛的阳离子依赖性氨基酸转运体基因（y+LAT-2）。
基于本研究结果，可以推测人鼻上皮表达L-氨基酸转运体。对这些转运体进行详细表征还需要更多研究。
