左旋肉碱在人角膜缘上皮细胞的转运特性

摘要

Objective To investigate the characteristics of L-carnitine (LC)import into human corneal limbal epithelia (HCLE)cells,and to provide an experimental basis for further study of transport mechanism of LC in human ocular epithelium.Methods The transport of [3 H ]-L-carnitine was determined using the radio uptake assay and the apparent kinetic parameters of carnitine uptake by HCLE were estimated by nonlinear regression curve fitting according to the Michaelis-Menten equation.Results The uptake of LC into HCLE cells was saturable and time-dependent,and it also required the presence of Na+ in the external medium.An Eadie-Hofstee plot showed two distinct components:a high-and a low-affinity carnitine transport system in HCLE cells.The unlabelled LC and acetyl-L-carnitine competitively inhibited the uptake of [3 H]-L-carnitine by HCLE cells.Conclusion L-carnitine is transported into HCLE cells from tears by an active carrier mediated transport system and exerts its biological function.%目的：检测左旋肉碱（L-carnitine，LC）在人角膜缘上皮（human corneal limbal epithelia，HCLE）细胞的转运特性，为进一步阐明 HCLE细胞对 LC的转运机制提供实验依据。方法采用放射摄入实验检测 HCLE细胞对[3 H]-L-carnitine的转运功能，并利用米氏方程（Michaelis-Menten equation）分析计算其动力学参数。结果HCLE细胞对 LC的转运过程具有饱和性和时间依赖性，并且反应体系中需要 Na＋的存在。Eadie-Hofstee作图提示 HCLE细胞存在高亲和力和低亲合力2个肉碱转运系统。非标记 LC和乙酰化左旋肉碱可竞争性抑制[3 H]-L-carnitine的转运过程。结论 HCLE细胞可通过主动转运过程将泪液中的左旋肉碱摄入细胞内，发挥其生物学功能。