Duffey M E, Devor D C
Department of Physiology, School of Medicine, State University of New York, Buffalo 14214.
Am J Physiol. 1990 Feb;258(2 Pt 1):C336-43. doi: 10.1152/ajpcell.1990.258.2.C336.
Intracellular pH (pHc) was measured in the short-circuited epithelium of rabbit distal colon using H(+)-selective microelectrodes. pHc was 6.91 +/- 0.02 (SE) when the bath pH was 7.4. Intracellular HCO3- activity (acHCO3-) was estimated from these measurements to be 8 +/- 0 mM. When we replaced all Cl- in the tissue bathing solutions with the impermeant anion gluconate, pHc rose to 7.44 +/- 0.08 and acHCO3- increased to 30 +/- 6 mM. These results demonstrate that this tissue contains a Cl(-)-HCO3- exchange mechanism. During the Cl- replacement the apical membrane electrical potential difference hyperpolarized from -55 +/- 1 to -74 +/- 3 mV, suggesting that membrane ionic conductance had changed. Elevation of either the apical or basolateral membrane bathing solution K+ concentration produced a greater depolarization of membrane potential during Cl- replacement than when tissues were bathed in normal electrolyte solutions. In additional experiments, pHc was raised by lowering the bath CO2 concentration while the bath Cl- concentration was kept normal. Under these conditions, membrane potential hyperpolarized and was more sensitive to the elevation of bath K+ concentration than when pHc was normal. These results suggest that membrane K+ conductance in this tissue is increased by intracellular alkalinization.
使用H(+)选择性微电极测量了兔远端结肠短路上皮细胞内的pH值（pHc）。当浴液pH值为7.4时，pHc为6.91±0.02（标准误）。根据这些测量结果估计细胞内HCO3-活性（acHCO3-）为8±0 mM。当我们用不透性阴离子葡萄糖酸盐替代组织浴液中的所有Cl-时，pHc升至7.44±0.08，acHCO3-增加到30±6 mM。这些结果表明该组织存在一种Cl(-)-HCO3-交换机制。在Cl-替代过程中，顶端膜电位差从-55±1 mV超极化至-74±3 mV，提示膜离子电导发生了变化。顶端或基底外侧膜浴液K+浓度升高时，与组织在正常电解质溶液中浸泡相比，Cl-替代过程中膜电位的去极化程度更大。在另外的实验中，通过降低浴液CO2浓度使pHc升高，同时保持浴液Cl-浓度正常。在这些条件下，膜电位超极化，并且与pHc正常时相比，对浴液K+浓度升高更敏感。这些结果提示该组织中的膜K+电导通过细胞内碱化而增加。
