Abedin M Z, Giurgiu D I, Abedin Z R, Peck E A, Su X, Smith P R
Department of Surgery, MCP Hahnemann University, Philadelphia, PA, USA.
J Membr Biol. 2001 Jul 15;182(2):123-34. doi: 10.1007/s00232-001-0038-9.
Gallbladder Na+ absorption is linked to gallstone formation in prairie dogs. Na+/H+ exchange (NHE) is one of the major Na+ absorptive pathways in gallbladder. In this study, we measured gallbladder Na+/H+ exchange and characterized the NHE isoforms expressed in prairie dogs. Na+/H+ exchange activity was assessed by measuring amiloride-inhibitable transepithelial Na+ flux and apical 22Na+ uptake using dimethylamiloride (DMA). HOE-694 was used to determine NHE2 and NHE3 contributions. Basal JNams was higher than JNasm with JNanet absorption. Mucosal DMA inhibited transepithelial Na+ flux in a dose-dependent fashion, causing JNams equal to JNasm and blocking JNanet absorption at 100 microm. Basal 22Na+ uptake rate was 10.9 +/- 1.0 micromol. cm-2. hr-1 which was inhibited by approximately 43% by mucosal DMA and approximately 30% by mucosal HOE-694 at 100 microm. RT-PCR and Northern blot analysis demonstrated expression of mRNAs encoding NHE1, NHE2 and NHE3 in the gallbladder. Expression of NHE1, NHE2 and NHE3 polypeptides was confirmed using isoform-specific anti-NHE antibodies. These data suggest that Na+/H+ exchange accounts for a substantial fraction of gallbladder apical Na+ entry and most of net Na+ absorption in prairie dogs. The NHE2 and NHE3 isoforms, but not NHE1, are involved in gallbladder apical Na+ uptake and transepithelial Na+ absorption.
草原犬鼠胆囊钠吸收与胆结石形成有关。钠/氢交换（NHE）是胆囊中主要的钠吸收途径之一。在本研究中，我们测量了草原犬鼠胆囊中的钠/氢交换，并对其表达的NHE亚型进行了表征。通过使用二甲基氨氯吡脒（DMA）测量氨氯吡脒抑制的跨上皮钠通量和顶端22钠摄取来评估钠/氢交换活性。HOE-694用于确定NHE2和NHE3的作用。基础跨上皮钠通量（JNams）高于净钠吸收量（JNasm），存在净钠吸收（JNanet）。黏膜DMA以剂量依赖性方式抑制跨上皮钠通量，使JNams等于JNasm，并在100微摩尔时阻断JNanet吸收。基础22钠摄取率为10.9±1.0微摩尔·厘米-2·小时-1，在100微摩尔时，黏膜DMA抑制约43%，黏膜HOE-694抑制约30%。逆转录聚合酶链反应（RT-PCR）和Northern印迹分析表明胆囊中存在编码NHE1、NHE2和NHE3的mRNA表达。使用亚型特异性抗NHE抗体证实了NHE1、NHE2和NHE3多肽的表达。这些数据表明，钠/氢交换在草原犬鼠胆囊顶端钠进入中占很大比例，并且是净钠吸收的主要方式。NHE2和NHE3亚型而非NHE1参与胆囊顶端钠摄取和跨上皮钠吸收。
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