Cellular and regional expression of transcripts of the plasma
membrane calcium pump pmca1 in rabbit intestine.
Freeman, Tom C., Alison Howard, Beint S. Bentsen, Stephen Legon, and
Julian R. F. Walters.
The Sanger Centre, Hinxton Hall, Hinxton, Cambs. CB10 1RQ, U.K.,
Gastroenterology Unit, Departments of Medicine & Chemical
Pathology, Royal Postgraduate Medical School, London W12 0NN,
U.K.
APStracts 2:0041G, 1995.
The plasma membrane calcium-pumping adenosinetriphosphatase (Ca2+
-ATPase, PMCA) is the energy-dependent step in the active, vitamin D
-dependent absorption of dietary calcium by the enterocyte. Studies of
the various PMCA genes and splicing variants in humans and rats have
indicated that the isoform known as PMCA1b is the predominant form
expressed in small intestine. We have now studied the regional and
cellular distribution of PMCA1 transcripts in rabbit intestinal
tissues by in situ hybridization using an oligonucleotide probe. On
small intestinal RNA blots, this hybridized to similar sized species
as those detected by PMCA1-specific cDNA probes; an additional larger
transcript was present in rabbit compared to rat or human. In situ
hybridization signals were principally in the enterocyte population
of the mucosa and were maximal in differentiating enterocytes on the
lower part of the villus, a pattern similar to that previously
demonstrated for other nutrient transporters. Reflecting the capacity
of the different small intestinal segments to transport calcium, much
higher levels of transcripts were detected by both methods proximally
(in duodenum) compared to distally (in jejunum and ileum), and were
also higher in cecum and ascending colon mucosa than in descending
colon. We conclude that as enterocytes differentiate in regions that
absorb calcium, they express high levels of mRNA for PMCA1. These
results confirm the importance of transcriptional regulation of this
gene for active calcium absorption.
Received 4 November 1994; accepted in final form 24 February
1995.
APS Manuscript Number G441-4.
Article publication pending Am. J. Physiol. (Gastrointest. Liver
Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 21 March 1995.