Intestinal distribution of human na+-h+ exchanger isoforms nhe-1,
nhe-2 and nhe-3 mrna.
Dudeja, Pradeep K., Donald D. Rao, Imran Syed, Virendra Joshi, Refka
Y. Dahdal, Crystal Gardner, Michael C. Risk, Larry Schmidt, Dipti
Bavishi, Karen E. Kim, James M. Harig, Jay L. Goldstein, Thomas J.
Layden, and Krishnamurthy Ramaswamy.
Section of Digestive and Liver Diseases, Dept. of Medicine, The
Univ. of Illinois at Chicago and Westside VA Medical Center, Chicago,
IL 60612
APStracts 3:0083G, 1996.
The identity of Na+-H+ exchanger (NHE) isoforms in the human small
intestine and colon and their role in vectorial Na+ absorption is not
known. The present studies were undertaken to examine the regional
and vertical axis distribution of NHE-1, NHE-2 and NHE-3 mRNA in the
human intestine. RNase protection assays were used to quantitate the
levels of mRNA of these isoforms in various regions of the human
intestine. In situ hybridization technique was performed to localize
NHE-2 and NHE-3 mRNA in the colon. The NHE-1 isoform message was
present uniformly throughout the length of the human intestine. In
contrast, the mRNA levels for human NHE-2 and NHE-3 isoforms
demonstrated significant regional differences. The NHE-3 abundance
was found in decreasing order: Ileum> jejunum>proximal
colon=distal colon. The NHE-2 message level in the distal colon was
significantly higher than in the proximal colon but was evenly
distributed in the small intestine. In addition, the NHE-2 mRNA was
existent in surface epithelial cells as well as in cells of the crypt
region, suggesting the presence of NHE-2 message throughout the
vertical axis of the colonic crypts. In contrast, the NHE-3 mRNA was
localized to the surface colonocytes in the proximal colon. Based on
this tissue specific localization of NHE-2 and NHE-3 mRNA, it can be
speculated that the relative contribution of NHE-2 and NHE-3 isoforms
in Na+ absorption in the human intestine may be region specific and
these putative apical isoforms may be differentially regulated.
Received 23 October 1995; accepted in final form 12 March 1996.
APS Manuscript Number G463-5.
Article publication pending Am. J. Physiol. (Gastrointest. Liver
Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 23 April 96