NHE-3 isoform of the Na+/H+ exchanger in human gallbladder. Localization of specific mRNA by in situ hybridization.
OBJECTIVE
Electroneutral absorption of NaCl by the gallbladder mucosa is likely to depend at least in part on a Na+/H+ exchanger. In intestine and colon, absorption due to Na+/H+ exchanger is explained by the presence of specific isoforms of the exchanger, the NHE-3 isoform and possibly the NHE-2 isoform. The aim of the present work was to determine whether the mRNAs coding for NHE-2 and NHE-3 are expressed in epithelial cells of human gallbladder.


METHODS
Total RNAs from human gallbladder were subjected to reverse transcription-polymerase chain reaction using specific primers. No message was observed with NHE-2 specific primers, showing that NHE-2 isoform plays no role in gallbladder absorption. With NHE-3 specific primers, a 239 bp cDNA fragment was obtained and showed a high homology with the NHE-3 isoform, confirming the presence of NHE-3 in the gallbladder wall. This fragment was cloned in a pLitmus vector in order to produce cRNA probes by in vitro transcription. Cellular localization of the NHE-3 mRNA was studied on cryostat sections using the cRNA probes labeled with Digoxigenin-11-UTP, controls included assays with sense probe, antibodies without probe and RNaseA treated tissue. A specific staining of the NHE-3 mRNAs was found to be strictly localized to the gallbladder epithelial cells.


CONCLUSIONS
Expression of NHE-3 in the gallbladder was found only in the absorptive epithelial cells. The NHE-3 isoform of the Na+/H+ exchanger is likely to be involved in water and electrolyte absorption from bile.
Silviani
V
V
INSERM U.260, Faculté de Médecine, Marseilles, France.
Gastaldi
M
M
Planells
R
R
Marteau
C
C
Massacrier
A
A
Cohen
P
P
Cau
P
P
Gerolami
A
A
D001483:Base Sequence; D017931:DNA Primers; D018076:DNA, Complementary; D004848:Epithelium / Q000378:metabolism; D005704:Gallbladder / Q000378:metabolism*; D006801:Humans; D017403:In Situ Hybridization; D008969:Molecular Sequence Data; D009092:Mucous Membrane / Q000378:metabolism; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000096:biosynthesis; D012689:Sequence Homology, Nucleic Acid; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers / Q000096:biosynthesis* / Q000235:genetics; D014158:Transcription, Genetic
D017931:DNA Primers; D018076:DNA, Complementary; D012333:RNA, Messenger; C000613385:SLC9A3 protein, human; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers