肉碱/有机阳离子转运体OCTN1/2在眼表上皮细胞的定位及功能

Localization and Function of Carnitine/Organic Cation Transporter OCTN1/2 in Ocular Epithelium

目的检测肉碱/有机阳离子转运体1/2(carnitine/organic cation transporter 1/2,OCTN1/2)在眼表上皮细胞的表达定位及转运功能,为进一步阐明左旋肉碱在人眼表上皮细胞的转运机制提供实验依据。方法采用免疫细胞化学的方法分别检测人角膜缘上皮(human corneal limbal epithelia,HCLE)细胞和人结膜上皮(human conjunctival epithelia,HCjE)细胞以及兔眼角膜和结膜上皮组织中OCTN1和OCTN2的表达定位;利用Ⅰ型胶原蛋白包被的双层培养板培养HCLE和HCjE细胞,并使之建立紧密连结,采用放射摄入实验检测其基底端和顶端转运[3 H]-L-carnitine的功能。结果 OCTN1和OCTN2蛋白在HCLE和HCjE细胞及兔眼角膜和结膜上皮组织中均有表达,且主要分布在细胞膜上;放射摄入实验结果表明HCLE和HCjE细胞均可转运[3 H]-L-carnitine,且大部分的左旋肉碱分子通过上皮细胞顶端摄入细胞内。结论 OCTN1和OCTN2主要分布在人角膜和结膜上皮细胞的顶端,且具有转运左旋肉碱进入细胞内的功能。

Objective To investigate the localization and transport function of carnitine/organic cation transporter 1/2（OC‐TN1/2） in ocular epithelium ,and to provide a structural and functional basis for further study of transport mechanism of L‐carnitine in human ocular epithelium.Methods Immunofluorescence staining was performed to investigate the localization of OCTN1 or OCTN2 in human ocular epithelial cells or rabbit corneal and conjunctival epithelium.Apical or basal uptake of [3 H]‐L‐carnitine was determined by using the polarized epithelial cells grown onto collagen‐coated porous filter support.Results OCTN1 and OCTN2 proteins were detected in HCLE and HCjE cells ,rabbit corneal and conjunctival epithelium ,and they were predominately located in the membranes of the cells. HCLE and HCjE cells were able to transfer [3 H]‐L‐carnitine and most L‐carnitine was uptaken through the apical part of the cells.Conclusion OCTN1 and OCTN2 are mainly located in the apical part of human corneal and conjunctival epithelial cells ,and they are potentially involved in the transport of L‐carnitine in ocular tis‐sues.