Expression of multiple Na+/H+ exchanger isoforms in rat parotid acinar and ductal cells.
Expression of multiple Na+/H+ exchanger isoforms in rat parotid acinar and ductal cells.
复制标题
大鼠腮腺腺泡和导管细胞中多种 Na /H 交换异构体的表达。
DOI：
10.1152/ajpgi.1999.276.2.g470
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发表时间：
1999
期刊：
影响因子：
--
通讯作者：
Melvin,JE
中科院分区：
文献类型：
--
作者：
Park,K;Olschowka,JA;Richardson,LA;Bookstein,C;Chang,EB;Melvin,JE
Na+/H+交换基因家族的几个成员（NHE 1、NHE 2、NHE 3和NHE 4）具有独特的功能特性，已从大鼠上皮组织中克隆。本研究探讨了大鼠腮腺细胞Na+/H+交换的分子和药理学特性。在用生理盐溶液（145 mM Na+）灌注的腺泡细胞中，低浓度的阿米洛利衍生物乙基异丙基阿米洛利（EIPA; IC 50 = 0.014 ± 0.005 μM）抑制Na+/H+交换活性，表明阿米洛利敏感亚型NHE 1和/或NHE 2的表达。半定量RT-PCR证实，NHE 1转录本是最丰富的这种细胞类型。相反，导管细胞对EIPA的中间敏感性表明，对EIPA敏感的和耐药的Na+/H+交换亚型共表达。导管细胞对EIPA的抗性（IC 50 = 0.754 ± 0.104 μM）比表达NHE 1或NHE 2的细胞系（IC 50分别为0.076 ± 0.013或0.055 ± 0.015 μM）高约一个数量级。相反，导管细胞对EIPA的敏感性比表达NHE 3亚型的细胞系高近一个数量级（IC 50 = 6.25 ± 1.89 μM）。半定量RT-PCR结果表明，NHE 1和NHE 3的转录本在导管中表达。NHE 1免疫定位于腺泡和导管细胞的基底外侧膜，而NHE 3仅见于导管细胞的顶膜。免疫印迹，免疫定位，和半定量RT-PCR实验未能检测到NHE 2的表达在任一种细胞类型。两者合计，我们的研究结果表明，NHE 1是占主导地位的功能Na+/H+交换器在大鼠腮腺腺泡细胞的质膜，而NHE 1和NHE 3的行动一致，以调节导管细胞内的pH值。
Several members of the Na+/H+exchanger gene family (NHE1, NHE2, NHE3, and NHE4) with unique functional properties have been cloned from rat epithelial tissues. The present study examined the molecular and pharmacological properties of Na+/H+exchange in rat parotid salivary gland cells. In acinar cells superfused with a physiological salt solution (145 mM Na+), Na+/H+exchanger activity was inhibited by low concentrations of the amiloride derivative ethylisopropyl amiloride (EIPA; IC50= 0.014 ± 0.005 μM), suggesting the expression of amiloride-sensitive isoforms NHE1 and/or NHE2. Semiquantitative RT-PCR confirmed that NHE1 transcripts are most abundant in this cell type. In contrast, the intermediate sensitivity of ductal cells to EIPA indicated that inhibitor-sensitive and -resistant Na+/H+exchanger isoforms are coexpressed. Ductal cells were about one order of magnitude more resistant to EIPA (IC50= 0.754 ± 0.104 μM) than cell lines expressing NHE1 or NHE2 (IC50= 0.076 ± 0.013 or 0.055 ± 0.015 μM, respectively). Conversely, ductal cells were nearly one order of magnitude more sensitive to EIPA than a cell line expressing the NHE3 isoform (IC50= 6.25 ± 1.89 μM). Semiquantitative RT-PCR demonstrated that both NHE1 and NHE3 transcripts are expressed in ducts. NHE1 was immunolocalized to the basolateral membranes of acinar and ductal cells, whereas NHE3 was exclusively seen in the apical membrane of ductal cells. Immunoblotting, immunolocalization, and semiquantitative RT-PCR experiments failed to detect NHE2 expression in either cell type. Taken together, our results demonstrate that NHE1 is the dominant functional Na+/H+exchanger in the plasma membrane of rat parotid acinar cells, whereas NHE1 and NHE3 act in concert to regulate the intracellular pH of ductal cells.