Newman E A, Astion M L
Eye Research Institute, Boston, Massachusetts 02114.
Glia. 1991;4(4):424-8. doi: 10.1002/glia.440040411.
An electrogenic Na+/HCO3- cotransport system was identified and characterized in freshly dissociated salamander Müller (glial) cells. Under voltage-clamp, these cells generated an outward current when external HCO3- concentration [( HCO3-]o) was raised. This current was Na(+)-dependent, Cl(-)-independent, and was blocked by the stilbenes 4,4'-diisothiocyanato-stilbene-2,2'-disulfonate (DIDS) and 4,4'-dinitrostilbene-2,2'-disulfonate (DNDS), and by harmaline, demonstrating that the current was generated by a Na+/HCO3- cotransport system. Substantially larger currents were evoked when [HCO3-]o was raised at the Müller cell endfoot as compared to other cell regions, indicating that cotransporter sites are localized preferentially to the endfoot. The reversal potential of the current, which varied as a function of HCO3- and Na+ transmembrane gradients, indicated that the cotransporter has a HCO3-:Na+ stoichiometry of 3:1.
在新鲜分离的蝾螈米勒（神经胶质）细胞中鉴定并表征了一种生电的Na⁺/HCO₃⁻共转运系统。在电压钳制下，当细胞外HCO₃⁻浓度[（HCO₃⁻）ₒ]升高时，这些细胞产生外向电流。该电流依赖于Na⁺，不依赖于Cl⁻，并被芪类化合物4,4'-二异硫氰酸根合芪-2,2'-二磺酸盐（DIDS）、4,4'-二硝基芪-2,2'-二磺酸盐（DNDS）以及骆驼蓬碱阻断，表明该电流由Na⁺/HCO₃⁻共转运系统产生。与其他细胞区域相比，当在米勒细胞终足处升高[HCO₃⁻]ₒ时，诱发的电流要大得多，这表明共转运体位点优先定位于终足。电流的反转电位随HCO₃⁻和Na⁺跨膜梯度而变化，表明共转运体的HCO₃⁻:Na⁺化学计量比为3:1。
