左旋肉碱在人角膜缘上皮细胞的转运特性

Transport of L-carnitine in human corneal epithelial cells

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[~3H]-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[~3H]-Lcarnitine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。

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[~3H]-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[~3H]-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.