Moschèn I, Setiawan I, Bröer S, Murer H, Lang F
Physiologisches Institut, Universität Tübingen, Germany.
Pflugers Arch. 2001 Mar;441(6):802-6. doi: 10.1007/s004240000481.
Extracellular pH has been shown previously to influence transport via type-II Na+/phosphate (NaPi) transporters by modifying the affinity of the carrier for Na+ and by altering the availability of divalent and monovalent phosphate. As the transport of monovalent phosphate would be expected to acidify, and that of divalent phosphate to alkalinize the cell interior, the effect of phosphate transport on cytosolic pH was studied using ion selective microelectrodes in Xenopus oocytes expressing NaPi-3 or NaPi-5. At an alkaline extracellular pH (pHe) of 8.0, addition of phosphate elicited a strong inward current, depolarization of the cell membrane and cytosolic alkalinization. At pHe 6.0 the phosphate-induced inward current and depolarization were reduced and the alkalinization completely abolished. In conclusion, at alkaline pHe phosphate transport is enhanced and the transport of divalent phosphate prevails. At pHe 6.0, phosphate transport is attenuated and is accomplished by transport of both divalent and monovalent phosphate.
先前的研究表明，细胞外pH可通过改变载体对Na+的亲和力以及改变二价和一价磷酸盐的可用性，来影响II型Na+/磷酸盐（NaPi）转运体的转运。由于一价磷酸盐的转运预计会使细胞内酸化，而二价磷酸盐的转运则会使细胞内碱化，因此我们使用离子选择性微电极，在表达NaPi-3或NaPi-5的非洲爪蟾卵母细胞中，研究了磷酸盐转运对细胞溶质pH的影响。在细胞外碱性pH（pHe）为8.0时，添加磷酸盐会引发强烈的内向电流、细胞膜去极化和细胞溶质碱化。在pHe 6.0时，磷酸盐诱导的内向电流和去极化减弱，碱化完全消失。总之，在碱性pHe条件下，磷酸盐转运增强，且以二价磷酸盐转运为主。在pHe 6.0时，磷酸盐转运减弱，且由二价和一价磷酸盐的转运共同完成。
