Boron W F, Boulpaep E L
J Gen Physiol. 1983 Jan;81(1):29-52. doi: 10.1085/jgp.81.1.29.
Using pH-sensitive microelectrodes to measure intracellular pH (pHi) in isolated, perfused proximal tubules of the tiger salamander Ambystoma tigrinum, we have found that when cells are acid-loaded by pretreatment with NH+4 in a nominally HCO3--free Ringer, pHi spontaneously recovers with an exponential time course. This pHi recovery, which is indicative of active (i.e., uphill) transport, is blocked by removal of Na+ from both the luminal and basolateral (i.e., bath) solutions. Re-addition of Na+ to either the lumen or the bath results in a full pHi recovery, but at a lower-than-normal rate; the maximal rate is achieved only with Na+ in both solutions. The diuretic amiloride reversibly inhibits the pHi recovery when present on either the luminal or basolateral sides, and has its maximal effect when present in both solutions. The pHi recovery is insensitive to stilbene derivatives and to Cl- removal. A transient rise of intracellular Na+ activity accompanies the pHi recovery; there is no change of intracellular Cl- activity. These data suggest that these proximal tubule cells have Na-H exchangers in both the luminal and basolateral membranes.
我们使用对pH敏感的微电极来测量虎螈（Ambystoma tigrinum）分离灌注的近端小管中的细胞内pH（pHi），发现当细胞在名义上无HCO3-的林格氏液中用NH+4预处理进行酸负荷时，pHi会以指数时间进程自发恢复。这种表明主动（即向上）转运的pHi恢复，会因从管腔和基底外侧（即浴液）溶液中去除Na+而受阻。向管腔或浴液中重新添加Na+会导致pHi完全恢复，但速率低于正常水平；只有当两种溶液中都有Na+时才能达到最大速率。利尿剂氨氯吡脒存在于管腔或基底外侧时，会可逆地抑制pHi恢复，当两种溶液中都存在时效果最大。pHi恢复对芪衍生物和去除Cl-不敏感。细胞内Na+活性会伴随pHi恢复而短暂升高；细胞内Cl-活性没有变化。这些数据表明，这些近端小管细胞在管腔和基底外侧膜中都有Na-H交换体。
