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 J Na ms was higher than J Na sm with J Na net absorption. Mucosal DMA inhibited transepithelial Na+ flux in a dose-dependent fashion, causing J Na ms equal to J Na sm and blocking J Na net absorption at 100 μm. Basal 22Na+ uptake rate was 10.9 ± 1.0 μmol · cm−2· hr−1 which was inhibited by ∼43% by mucosal DMA and ∼30% by mucosal HOE-694 at 100 μm. 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.
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Received: 9 February 2001/Revised: 11 April 2001
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Abedin, M., Giurgiu, D., Abedin, Z. et al. Characterization of Na+/H+ Exchanger Isoform (NHE1, NHE2 and NHE3) Expression in Prairie Dog Gallbladder. J. Membrane Biol. 182, 123–134 (2001). https://doi.org/10.1007/s00232-001-0038-9
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DOI: https://doi.org/10.1007/s00232-001-0038-9