Mechanisms behind changes in gastric acid and bicarbonate outputs
during the human interdigestive motility cycle.
Dalenb[umlaut]ack, Jan, Lars F[umlaut]andriks, Lars Olbe, and Henrik
Sj[diaeresis]ovall.
Department of Surgery, Department of Physiology*, Department of
Internal Medicine, Centre of Gastrointestinal Research, Sahlgrenska
University Hospital, University of Gothenburg, SWEDEN
APStracts 2:0145G, 1995.
Human gastric interdigestive acid and bicarbonate outputs vary
cyclically in association with the migrating motor complex (MMC).
These phenomena were studied in 26 healthy volunteers by constant
-flow gastric perfusion, with continuous recording of pH and PCO2 in
mixed gastric effluent, and concomitant open-tip manometry of gastro
-duodenal motility. Stable acid and bicarbonate outputs were
registered during less than 50% of the MMC-cycle. Acid secretion
started to increase 71+/-3% into the cycle, with maximum output
during antral phase III. Bicarbonate output increased biphasically:
1) 40+/-5% into the cycle, coinciding with reflux of bile, and 2) at
the end of duodenal phase III when the aspirate was devoid of bile.
The phase III associated bicarbonate peak was abolished by atropine
(0.01 mg/kg i.v., n=8), and by pyloric occlusion (n=9) but unchanged
after omeprazole (n=10). The acid peak was abolished by both atropine
ane omeprazole. It is concluded that the MMC-related changes in acid
and alkaline outputs represent two different and independent
phenomena. Acid secretion cyclicity is due to periodical variations
in cholinergic stimulation of the parietal cells. In contrast, the
phase III associated increase in bicarbonate output is due to
duodenogastric reflux.
Received 4 May 1994; accepted in final form 14 July 1995.
APS Manuscript Number G166-4.
Article publication pending Am. J. Physiol. (Gastrointest. Liver
Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 30 July 1995.