Membrane-limited expression and regulation of Na+-H+ exchanger isoforms by P2 receptors in the rat submandibular gland duct
Membrane-limited expression and regulation of Na+-H+ exchanger isoforms by P2 receptors in the rat submandibular gland duct
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DOI：
10.1111/j.1469-7793.1998.341bb.x
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发表时间：
1998-12-01
影响因子：
5.5
通讯作者：
Muallem, S
中科院分区：
文献类型：
--
作者：
Lee, MG;Schultheis, PJ;Muallem, S
1. 采用细胞特异性逆转录聚合酶链反应（RT-POR）、免疫定位和显微荧光法对颌下腺（SMG）腺泡和导管细胞中表达的Na+-H+交换剂（NHE）亚型进行了鉴定和定位，并对其进行了基底侧和腔内P-2受体的调控。分子和免疫荧光分析显示SMG腺泡和导管细胞在基底外侧膜（BLM）中表达NHE1。导管细胞在管腔膜（LM）中也表达NHE2和NHE3。NHE3基因敲除小鼠的SMG中没有染色，明确确定了NHE3的表达。NHE3在LM和管腔下区表达。用amiloride类似物ho694 （HOE）对NHE活性的抑制测量表明，nhe1样活性在BLM中表达，nhe2样活性在SMG导管LM中表达。测试的几种急慢性治疗未能激活NHE活性，与预期的NHE3一样，对HOE具有低亲和力。因此，NHE3在SMG导管中的生理功能和作用目前尚不清楚。P-2受体的激活导致一个不依赖于nhe的腔内H+运输途径的激活，该途径显著且迅速地使细胞酸化。该途径可被管腔而非基底外侧Ba2+阻断。刺激BLM中表达的P-2U受体可大量激活nhe1样活性，刺激LM中表达的P-2Z受体可大量激活nhe2样活性。基底外侧和腔内NHE活性之间的相互关系以及P-2U和P-2Z受体对它们各自的调节可用于协调SMG导管在活性Na+重吸收过程中LM和BLM中的膜运输事件。
1. Cell-specific reverse transcriptase-polymerase chain reaction (RT-POR), immunolocalization and microspectrofluorometry were used to identify and localize the Na+-H+ exchanger (NHE) isoforms expressed in the submandibular gland (SMG) acinar and duct cells and their regulation by basolateral and luminal P-2 receptors in the duct.2. The molecular and immunofluorescence analysis showed that SMG acinar and duct cells expressed NHE1 in the basolateral membrane (BLM). Duct cells also expressed NHE2 and NHE3 in the luminal membrane (LM).3. Expression of NHE3 was unequivocally established by the absence of staining in SMG from NHE3 knockout mice. NHE3 was expressed in the LM and in subluminal regions of the duct.4. Measurement of the inhibition of NHE activity by the amiloride analogue HOE 694 (HOE) suggested expression of NHE1-like activity in the BLM and NHE2-like activity in the LM of the SMG duct. Several acute and chronic treatments tested failed to activate NHE activity with low affinity for HOE as expected for NHE3. Hence, the physiological function and role of NHE3 in the SMG duct is not clear at present.5. Activation of P-2 receptors resulted in activation of an NHE-independent, luminal H+ transport pathway that markedly and rapidly acidified the cells. This pathway could be blocked by luminal but not basolateral Ba2+.6. Stimulation of P-2U receptors expressed in the BLM activated largely NHE1-like activity, and stimulation of P-2Z receptors expressed in the LM activated largely NHE2-like activity.7. The interrelation between basolateral and luminal NHE activities and their respective regulation by P-2U and P-2Z receptors can be used to co-ordinate membrane transport events in the LM and BLM during active Na+ reabsorption by the SMG duct.