Effect of pH on membrane potential and K+ conductance in cultured rat hepatocytes.
Effect of pH on membrane potential and K+ conductance in cultured rat hepatocytes.
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pH 对培养大鼠肝细胞膜电位和 K 电导的影响。
DOI：
10.1152/ajpgi.1989.257.6.g961
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发表时间：
1989
期刊：
影响因子：
--
通讯作者：
Scharschmidt,BF
中科院分区：
文献类型：
--
作者：
Fitz,JG;Trouillot,TE;Scharschmidt,BF
本文研究了原代培养大鼠肝细胞的细胞外pH（pHo）和细胞内pH（pHi）对膜电位差（PD）和细胞电导（gcell）的影响。在细胞外灌注液的pH或离子组成突然变化期间，分别通过使用细胞内微电极和pH敏感的荧光染料2 '，7'-双（2-羧乙基）-5（6）-羧基荧光素（BCECF）连续测量PD和pHi。在25 mM HCO 3-存在下，PD、gcell和pHi的平均值分别为（+/- SE）-32 +/- 1 mV、16.4 +/- 1.0 nS和7.32 +/- 0.01。K+的迁移数（tk+）反映了K+电导对gcell的贡献分数，平均为0.36 +/- 0.03。暴露于1 mM Ba 2+产生膜去极化，并使tK+降低约90%。在存在和不存在HCO 3的情况下，通过各种操作降低pHo-持续降低pHi，降低gcell（pHi每单位变化约30 nS）和去极化PD。增加pH值有相反的影响，但在gcell的变化一般是更大的细胞内酸化比碱化。通过降低pH值产生的PD减少与tK+减少73 +/- 2%相关，并被Ba 2+抑制。丁酸盐暴露或NH+4撤除均能降低pHi而不改变pHo，也能引起PD去极化和g细胞减少，而Ba ~（2+）则能抑制g细胞减少。这些观察结果表明，PD的肝细胞是强烈影响的pH值，有或没有变化的pH值，他们进一步表明，pH值对PD的影响是通过质膜K+电导的变化介导的。
We have investigated the effects of extracellular (pHo) and intracellular (pHi) pH on membrane potential difference (PD) and cell conductance (gcell) in rat hepatocytes in primary culture. PD and pHi were measured continuously by using intracellular microelectrodes and the pH-sensitive fluorochrome 2',7'-bis(2-carboxyethyl)-5(6)-carboxy fluorescein (BCECF), respectively, during abrupt changes in the pHo or ionic composition of extracellular perfusate. In the presence of 25 mM HCO3-, PD, gcell, and pHi averaged (+/- SE) -32 +/- 1 mV, 16.4 +/- 1.0 nS, and 7.32 +/- 0.01, respectively. The transference number for K+ (tk+), which reflects the fractional contribution of K+ conductance to gcell, averaged 0.36 +/- 0.03. Exposure to 1 mM Ba2+ produced membrane depolarization and decreased tK+ by approximately 90%. Lowering pHo by a variety of maneuvers in the presence and absence of HCO3- consistently decreased pHi, decreased gcell (approximately 30 nS per unit change in pHi), and depolarized PD. Increasing pHo had opposite effects, but the changes in gcell were generally greater with intracellular acidification than alkalinization. The decrease in PD produced by lowering pHo was associated with a decrease in tK+ of 73 +/- 2% and was inhibited by Ba2+. Exposure to butyrate or withdrawal of NH+4, which lowered pHi without changing pHo, also caused depolarization of PD and a decrease in gcell that was inhibited by Ba2+. These observations indicate that the PD of hepatocytes is strongly influenced by pHi, with or without changes in pHo, and they further suggest that the effects of pH on PD are mediated through changes in plasma membrane K+ conductance.