title: Acid incubation increases NHE-3 mRNA abundance in OKP cells.
abstract: With the use of degenerate primers based on conserved amino acid sequences in human, rat, and rabbit Na/H exchanger-3 (NHE-3), a polymerase chain reaction product was obtained from reverse-transcribed OKP (a clonal opossum kidney cell line) mRNA and used to screen an OKP cDNA library. The clone obtained predicted an amino acid sequence that was 86% identical to rat NHE-3, 33% to NHE-1, 35% to NHE-2, and 30% to NHE-4. Expression of the corresponding cRNA in Xenopus oocytes induced 22Na uptake with ethylisopropylamiloride. (EIPA) resistance similar to that of the OKP Na/H antiporter. On RNA blot, the cDNA labeled a 9.5-kb transcript whose abundance was increased 2.2-fold by 24-h incubation of OKP cells at pH 7.0 and 2.5-fold by 24-h incubation at pH 6.8. The acid-induced increase in NHE-3 mRNA was detectable at 12 h and increased further at 24 h. Incubation in acid media caused an increase in EIPA-resistant Na/H antiporter activity that preceded the increase in NHE-3 mRNA. In summary, OKP cells express an NHE-3 transcript that encodes an EIPA-resistant Na/H antiporter and is chronically regulated by acid.
authors.affiliation: Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas 75235-8856, USA.
authors.forename: M
authors.initials: M
authors.lastname: Amemiya
authors.forename: Y
authors.initials: Y
authors.lastname: Yamaji
authors.forename: A
authors.initials: A
authors.lastname: Cano
authors.forename: O W
authors.initials: OW
authors.lastname: Moe
authors.forename: R J
authors.initials: RJ
authors.lastname: Alpern
mesh_terms: D000143:Acids / Q000494:pharmacology*; D000584:Amiloride / Q000031:analogs & derivatives / Q000494:pharmacology; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D004351:Drug Resistance; D006863:Hydrogen-Ion Concentration; D007668:Kidney / Q000166:cytology / Q000378:metabolism; D015335:Molecular Probes / Q000235:genetics; D008969:Molecular Sequence Data; D009865:Oocytes / Q000378:metabolism; D009893:Opossums; D012333:RNA, Messenger / Q000378:metabolism*; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers / Q000235:genetics* / Q000378:metabolism; D014982:Xenopus laevis
chemical_list: D000143:Acids; D015335:Molecular Probes; D012333:RNA, Messenger; C000613385:SLC9A3 protein, human; C000613387:Slc9a3 protein, rat; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers; D000584:Amiloride; C039614:ethylisopropylamiloride