Hillenkamp Jost, Hussain Ali A, Jackson Timothy L, Cunningham Joanna R, Marshall John
Department of Ophthalmology, The Rayne Institute, St Thomas' Hospital, Lambeth Palace Road, London SE1 7EH, UK.
Exp Eye Res. 2006 Feb;82(2):258-64. doi: 10.1016/j.exer.2005.06.020. Epub 2005 Aug 18.
The purpose of this study was to assess the effect of taurine and apical potassium concentration modelling in vivo light evoked changes on the transepithelial potential (TEP) and the transepithelial resistance (TER) of isolated bovine retinal pigment epithelium (RPE). Isolated specimens of bovine non-tapetal RPE-Bruch's-choroid (RPE-BC) were mounted in modified Ussing chambers. The apical and the basolateral side of the preparations were exposed to 10 mm and 10 microm concentrations of taurine in Krebs' medium with either 6.04 or 2.2 mm potassium in the apical compartment. TEP and TER were recorded over 140 min. TEP and TER decreased with exposure to taurine over the course of 1 hr followed by a stabilisation. The degree of this response did not depend on the concentration of taurine but was more pronounced when taurine was added to the apical compartment. Lowering apical potassium from 6.04 to 2.2 mm further pronounced the decrease of TEP and TER. The data show that light-induced release of taurine from the outer retina and light-induced decrease of the potassium concentration in the subretinal space synergistically lead to a temporary decrease in TEP and TER. Thereby, taurine uptake into the RPE is reduced probably by a reduction of the activity of the electrogenic Na+/taurine co-transporter of the apical RPE cell membrane. The findings suggest a mechanism whereby the sustained presence of taurine in the interphotoreceptor matrix following exposure to light may protect photoreceptor outer segments from light-induced oxidative stress.
本研究的目的是评估牛磺酸和顶端钾离子浓度建模对离体牛视网膜色素上皮（RPE）的跨上皮电位（TEP）和跨上皮电阻（TER）的体内光诱发变化的影响。将牛非绒毡层视网膜色素上皮-脉络膜（RPE-BC）的离体标本安装在改良的Ussing小室中。制剂的顶端和基底外侧分别暴露于含有10 mM牛磺酸的Krebs培养基中，顶端隔室中的钾离子浓度分别为6.04 mM或2.2 mM。在140分钟内记录TEP和TER。在1小时内，TEP和TER随着牛磺酸的暴露而降低，随后趋于稳定。这种反应的程度不取决于牛磺酸的浓度，但当牛磺酸添加到顶端隔室时更为明显。将顶端钾离子浓度从6.04 mM降低到2.2 mM进一步加剧了TEP和TER的降低。数据表明，光诱导的牛磺酸从视网膜外层释放以及光诱导的视网膜下间隙钾离子浓度降低协同导致TEP和TER暂时降低。由此，可能通过降低顶端RPE细胞膜上的电中性Na+/牛磺酸共转运体的活性，减少了牛磺酸向RPE的摄取。这些发现提示了一种机制，即光照后感光细胞间基质中牛磺酸的持续存在可能保护光感受器外段免受光诱导的氧化应激。
