Role of basolateral na-k-cl cotransport in hcl secretion by
amphibian gastric mucosa.
Soybel, David I., Steven R. Gullans, Francis Maxwell, and Eric
Delpire.
Department of Surgery and Renal Division, Department of Medicine,
Brigham and Women's Hospital, Boston, MA 02115
APStracts 2:0153C, 1995.
In amphibians and mammals, luminal H+ secretion by the stomach
requires Cl- ions. It is widely accepted that a basolateral Cl-/HCO3-
exchanger in the acid-secreting oxyntic cell restores the Cl- deficit
resulting from apical HCl secretion. In this study, we used reverse
transcriptase- polymerase chain reaction (RT-PCR) to generate a 1200
bp fragment specific to a basolateral isoform of the Na-K-Cl
cotransporter in the gastric fundus of Necturus maculosus. By
Northern analysis, we observed that gastric mucosa expresses >5
-fold higher levels of mRNA encoding this cotransporter than any other
tissue in the gastrointestinal tract. Feeding results in >100%
increases in mRNA levels in acid-secreting fundic mucosa but does not
alter mRNA levels in the neighboring and non acid-secreting antral
mucosa or duodenum. Flux measurements using in vitro fundic mucosae
indicate that acid secretion requires Na+ in the nutrient (i.e.,
serosal side) perfusate, is modulated by changes in nutrient K+
levels, and is inhibited by nutrient solutions containing 50 [mu]M
bumetanide, a recognized blocker of Na-K-Cl cotransport. These
findings suggest that this basolateral transporter plays a dominant
and previously unsuspected role in secretion of HCl across the apical
membrane.
Received 21 September 1994; accepted in final form 12 January
1995.
APS Manuscript Number C570-4.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 4 April 1995.