Is resting state HCO3- secretion in frog gastric fundus mucosa mediated by apical Cl--HCO3- exchange?
Is resting state HCO3- secretion in frog gastric fundus mucosa mediated by apical Cl--HCO3- exchange?
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DOI：
10.1113/jphysiol.1997.sp021967
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发表时间：
1997-03-15
影响因子：
5.5
通讯作者：
Curci, S
中科院分区：
文献类型：
--
作者：
Caroppo, R;Debellis, L;Curci, S
1. 我们测试了广泛接受的假设，即胃底粘膜静息态碳酸氢盐分泌是由表面上皮细胞（SEC）顶膜中的 Cl--HCO3- 交换介导的。为此，用双管微电极刺穿离体林蛙眼底粘膜的 SEC，测量细胞内 pH (pH(i))2。没有观察到响应管腔 HCO3- 和/或 Cl- 浓度变化的显着 pH(i) 变化。响应鲁米那氯化物替代的 pH(i) 变化 (Delta pH(i)) 平均为 0.00 +/- 0.01 pH 单位（平均值 +/-S.E.M.；n = 48），并且在阻断可能掩盖 pH(i) 响应的假定基底外侧酸/碱转运蛋白后没有变化。 3.另一方面，pH(i) 对低 pH (pH 2.5) 溶液（Delta pK(i) = 0.36 +/- 0.05；n = 4；P < 0.01）或不含 CO2 的 HCO3- Ringer 溶液（Delta pH(i) = +0.10 +/- 0.01；n = 29；P < 0.001）的管腔灌注有容易且可逆的反应。这些观察结果表明，溶液更换在 1 分钟内有效且完成，并表明 SEC 的顶膜可渗透 CO2.4。青蛙 SEC 的顶膜不能用针对小鼠 Cl--HCO3-交换异构体 AE2 的 C 末端的抗体进行染色，尽管该抗体很容易对泌酸细胞 (OC) 的基底外侧膜进行染色。5。总之，不能证实静息状态下蛙胃底粘膜SEC顶膜中存在Cl--HCO3-交换剂，但不能完全排除其他HCO3-分泌模型。电测量的观察结果支持传导性 HCO3- 分泌模型，指出 OC 而不是 SEC 作为 HCO3- 分泌的起源位点。
1. We have tested the widely accepted hypothesis that resting-state bicarbonate secretion of gastric fundus mucosa is mediated by Cl--HCO3- exchange in the apical membrane of surface epithelial cells (SECs). To this end, SECs of isolated fundus mucosa of Rana esculenta were punctured with double-barrelled microelectrodes to measure intracellular pH (pH(i))2. No significant pH(i) changes were observed in response to changing luminal HCO3- and/or Cl- concentrations. The change in pH(i) (Delta pH(i)) in response to luminal chloride substitution averaged 0.00 +/- 0.01 pH units (mean +/-S.E.M.; n = 48), and did not change after blocking putative basolateral acid/base transporters which could have masked the pH(i) response.3. On the other hand, pH(i) responded readily and reversibly to luminal perfusion with either low-pH (pH 2.5) solution (Delta pK(i) = 0.36 +/- 0.05; n = 4; P < 0.01) or CO2-free HCO3- Ringer solution (Delta pH(i) = +0.10 +/- 0.01; n = 29; P < 0.001). These observations demonstrate that the solution change was effective and complete within 1 min and show that the apical membrane of SECs is permeable to CO2.4. The apical membrane of frog SECs could not be stained with an antibody against the C-terminal end of the mouse Cl--HCO3- exchanger isoform AE2, although this antibody readily stained the basolateral membrane of the oxyntopeptic cells (OCs).5. In conclusion, the presence of a Cl--HCO3- exchanger in the apical membrane of SECs of frog gastric fundus mucosa in the resting state could not be confirmed, but other models of HCO3- secretion cannot be fully excluded. Observations from electrical measurements, favouring a model of conductive HCO3- secretion, point to the OCs rather than the SECs as a site of origin of HCO3- secretion.