title: Characterization of NA+/H+ exchanger isoform (NHE1, NH32 and NHE3) expression in prairie dog gallbladder.
abstract: 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.
authors.affiliation: Department of Surgery, MCP Hahnemann University, Philadelphia, PA, USA.
authors.forename: M Z
authors.initials: MZ
authors.lastname: Abedin
authors.forename: D I
authors.initials: DI
authors.lastname: Giurgiu
authors.forename: Z R
authors.initials: ZR
authors.lastname: Abedin
authors.forename: E A
authors.initials: EA
authors.lastname: Peck
authors.forename: X
authors.initials: X
authors.lastname: Su
authors.forename: P R
authors.initials: PR
authors.lastname: Smith
mesh_terms: D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D001693:Biological Transport, Active; D015152:Blotting, Northern; D002769:Cholelithiasis / Q000378:metabolism*; D004195:Disease Models, Animal; D004594:Electrophysiology; D004847:Epithelial Cells; D005704:Gallbladder / Q000187:drug effects / Q000378:metabolism*; D006146:Guanidines / Q000494:pharmacology; D015151:Immunoblotting; D008297:Male; D020033:Protein Isoforms / Q000096:biosynthesis / Q000235:genetics; D012313:RNA / Q000302:isolation & purification; D012589:Sciuridae; D012964:Sodium / Q000378:metabolism*; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers / Q000096:biosynthesis* / Q000235:genetics; D013450:Sulfones / Q000494:pharmacology
chemical_list: D006146:Guanidines; D020033:Protein Isoforms; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers; D013450:Sulfones; C069139:growth factor-activatable Na-H exchanger NHE-1; C074107:3-methylsulfonyl-4-piperidinobenzoyl guanidine; D012313:RNA; D000584:Amiloride; D012964:Sodium