Function and regulation of taurine transport at the inner blood–retinal barrier

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• 作者：Masatoshi Tomi ; Tomoyuki Terayama ; Tomoyuki Isobe ; Fuminobu Egami ; Akihisa Morito ; Michio Kurachi ; Sumio Ohtsuki ; Young-Sook Kang ; Tetsuya Terasaki ; Ken-ichi Hosoya
• 关键词：Inner blood– ; retinal barrier ; Taurine ; Transporter ; Retina ; Endothelial cells
• 刊名：Microvascular Research
• 出版年：2007
• 期刊代码：301_00262862
• 类别：med
• 出版时间：March 2007
• 卷：73
• 期：2
• 页码：100-106
• 文件大小：379 K

摘要

In the retina, taurine exerts a number of neuroprotective functions as an osmolyte and antioxidant. The purpose of the present study was to elucidate the taurine transport system(s) at the inner blood–retinal barrier (BRB). [³H]Taurine transport at the inner BRB was characterized using in vivo integration plot analysis and a conditionally immortalized rat retinal capillary endothelial cell line (TR-iBRB2 cells). The expression of the taurine transporter (TauT) was demonstrated by RT-PCR and immunoblot analyses. The apparent influx permeability clearance of [³H]taurine in the rat retina was found to be 259 μL/(ming retina), supporting carrier-mediated influx transport of taurine at the BRB. [³H]Taurine uptake by TR-iBRB2 cells was Na⁺-, Cl⁻- and concentration-dependent with a K_m of 22.2 μM and inhibited by TauT inhibitors, such as β-alanine and hypotaurine. RT-PCR and immunoblot analyses demonstrated that TauT is expressed in TR-iBRB2 and primary cultured human retinal endothelial cells. The uptake of [³H]taurine and the expression of TauT mRNA in TR-iBRB2 cells increased under hypertonic conditions but decreased following pretreatment with excess taurine. In conclusion, TauT most likely mediates taurine transport and regulate taurine transport at the inner BRB.