Regulation of cholecystokinin secretion by intraluminal releasing
factors.
Liddle, Rodger A.
Department of Medicine, Duke University Medical Center and Durham
VA Medical Center, Durham, NC 27710
APStracts 2:0109G, 1995.
Ingested nutrients stimulate secretion of gastrointestinal hormones
that are necessary for the coordinated processes of digestion and
absorption of food. One of the most important hormonal regulators of
the digestive process is cholecystokinin (CCK). This hormone is
concentrated in the proximal small intestine and is secreted into the
blood upon the ingestion of proteins and fats. The physiologic
actions of CCK include stimulation of pancreatic secretion and
gallbladder contraction, regulation of gastric emptying, and
induction of satiety. Therefore, in a highly coordinated manner CCK
regulates the ingestion, digestion, and absorption of nutrients. The
manner by which foods affect enteric hormone secretion is largely
unknown. However, it has recently become apparent that two
"CCK releasing factors" are present in the lumen of the
proximal small intestine. One of these factors, known as monitor
peptide, has been chemically characterized. Monitor peptide is
produced by pancreatic acinar cells and is secreted by way of the
pancreatic duct into the duodenum. Upon reaching the small intestine,
monitor peptide interacts with CCK cells to induce hormone secretion.
A CCK-releasing factor of intestinal origin has been partially
characterized and is responsible for stimulation of CCK secretion
following (i) ingestion of protein or fats, (ii) instillation of
protease inhibitors into the duodenum, or (iii) diversion of bile
-pancreatic juice from the upper small intestine. Together, these
releasing factors provide positive and negative feedback mechanisms
for regulation of CCK secretion. This review will discuss the
physiological observations that have led to the chemical
characterization of the CCK releasing factors and the potential
implications of this work to other hormones of the gastrointestinal
tract.
Received 16 January 1995; accepted in final form 15 May 1995.
APS Manuscript Number G214-5.
Article publication pending Am. J. Physiol. (Gastrointest. Liver
Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 8 June 1995.