Incubation increases nhe-3 mrna abundance in okp cells.
Amemiya, Morimasa, Yasuyoshi Yamaji, Adriana Cano, Orson W. Moe, and
Robert J. Alpern.
Department of Internal Medicine, University of Texas Southwestern
Medical Center at Dallas, Dallas, TX 75235-8856
APStracts 2:0124C, 1995.
Using degenerate primers based on conserved amino acid sequences in
human, rat, and rabbit NHE-3, a PCR 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 labelled 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
ethylisopropylamiloride-resistant Na/H antiporter and is chronically
regulated by acid.
Received 22 November 1994; accepted in final form 13 January
1995.
APS Manuscript Number C689-4.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 10 March 1995.