title: Subcloning, localization, and expression of the rat intestinal sodium-hydrogen exchanger isoform 8.
abstract: Apically expressed intestinal and renal sodium-hydrogen exchangers (NHEs) play a major role in Na(+) absorption. Our previous studies on NHE ontogeny have shown that NHE-2 and NHE-3 are expressed at very low levels in young animals. Furthermore, single and/or double NHE-2 and NHE-3 knockout mice display no obvious abnormalities before weaning. These observations suggest that other transporter(s) may be involved in intestinal Na+ absorption during early life. The present studies were designed to clone the novel rat intestinal NHE-8 cDNA and to decipher the NHE-8 protein localization and gene expression pattern during different developmental stages. The rat NHE-8 cDNA has 2,160 bp and encodes a 575-amino acid protein. An antibody against NHE-8 protein was developed. Immunohistochemistry staining indicated apical localization of NHE-8 protein in rat intestinal epithelial cells. The apical localization of NHE-8 was also confirmed by its presence in brush-border membrane and its absence in basolateral membrane preparations. Northern blotting utilizing a NHE-8-specific probe demonstrated higher NHE-8 mRNA expression in young animals compared with adult animals. Western blot analysis revealed a similar pattern. Tissue distribution with multiple human tissue RNA blot showed that NHE-8 was expressed in multiple tissues including the gastrointestinal tract. In conclusion, we have cloned the full-length NHE-8 cDNA from rat intestine and further showed its apical localization in intestinal epithelial cells. We have also shown that NHE-8 gene expression and protein expression were regulated during ontogeny. Our data suggests that NHE-8 may play an important role in intestinal Na+ absorption during early life.
authors.affiliation: Department of Pediatrics, Steele Memorial Children's Research Center, 1501 N. Campbell Ave., Tucson, AZ 85724, USA.
authors.forename: Hua
authors.initials: H
authors.lastname: Xu
authors.forename: Rongji
authors.initials: R
authors.lastname: Chen
authors.forename: Fayez K
authors.initials: FK
authors.lastname: Ghishan
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D003001:Cloning, Molecular; D015723:Gene Library; D006859:Hydrogen; D007408:Intestinal Absorption / Q000235:genetics; D007413:Intestinal Mucosa / Q000502:physiology*; D008297:Male; D008969:Molecular Sequence Data; D051381:Rats; D017207:Rats, Sprague-Dawley; D012964:Sodium / Q000378:metabolism; D017923:Sodium-Hydrogen Exchangers / Q000235:genetics* / Q000378:metabolism*
chemical_list: C502388:Slc9a8 protein, rat; D017923:Sodium-Hydrogen Exchangers; D006859:Hydrogen; D012964:Sodium