Role of CCK in gallbladder function.

Cholecystokinin may play a role in regulation of interdigestive motility, but this still remains to be investigated. CCK constitutes the major hormonal stimulus for postprandial gallbladder emptying. CCK exerts its contractile effects mainly through interaction directly with receptors on the gallbladder smooth muscle cells in the muscle layer, but also through interaction with cholinergic nerves extrinsic and/or intrinsic in nature. Furthermore, CCK can enhance ongoing nicotinic ganglionic transmission occurring in the serosal layer by release of acetylcholine. CCK interaction with the gallbladder smooth muscle CCKA receptor was studied in further detail. CCK contracts strips of gallbladder muscle in a concentration-dependent way with a potency in the nanomolar range in all tested species. The potency is 1,000-fold better than that of gastrin; thus, the receptor is of type CCKA. CCK binding to this receptor is specific and of high affinity, 1,000-fold better than that of gastrin with no differences between the tested species including bovine, porcine, and human. Also, CCK binding affinity was independent of age, gender, or weight of the person and pathology of the human gallbladder. The biochemistry of the CCKA receptor varies between the tested species (bovine and human). Both CCKA receptors are heavily glycosylated, but of different size and carbohydrate content. The bovine CCKA receptor is of apparent size M(r) = 70-85 kD with N-linked complex carbohydrates and sialic acids. The human CCKA receptor is of M(r) = 85-95 kD, with N-linked complex carbohydrates, but no sialic acids. They both have a protein core of apparent size M(r) = 43 kD, with almost identically sized fragments after enzymatic cleavage. Probably the protein cores contain the receptor binding region, which seems well preserved between species. CCK and the CCKA gallbladder muscularis receptor are main regulators of postprandial gallbladder emptying. The biochemistry of the CCKA gallbladder smooth muscle receptor is in accord with newly generated data of purification and cloning of the rat pancreatic CCKA receptor.

Gallbladder CCK receptors: species differences in glycosylation of similar protein cores.

Receptors for cholecystokinin (CCK) on gallbladder muscularis smooth muscle have different apparent sizes in man (Mr = 85,000-95,000) and cow (Mr = 70,000-85,000). In this work, these receptors were demonstrated to represent N-linked complex glycoproteins with Mr = 43,000 protein cores, based on lectin-affinity chromatography and the deglycosylation of bands affinity labeled with 125I-D-Tyr-Gly-[(Nle28,31, pNO2-Phe33)CCK-26-33] using neuraminidase, O-glycanase and endoglycosidases H and F. Similarities in the core proteins were further demonstrated by Staphylococcus aureus V8 protease peptide mapping, in which both proteins yielded similar fragment patterns. Thus, gallbladder CCK receptors present in man and cow are both N-linked complex glycoproteins, with different carbohydrate domains and similar protein cores.

Peptide-evoked release of amylase from isolated acini of the rat parotid gland.

Investigations of the effects of the neuropeptides, substance P (SP), neurokinin A (NKA), neuropeptide K (NPK), gastrin releasing peptide (GRP), calcitonin gene related peptide (CGRP) and vasoactive intestinal peptide (VIP), and of acetylcholine on amylase secretion have been carried out on isolated acini of the rat parotid gland. Furthermore, the occurrence and location of the peptides in the gland was studied. Finally, binding of 125I-BH-SP to isolated acini were studied in order to characterize their tachykinin receptor(s) and their binding kinetics. Only SP, NKA, NPK and VIP stimulated amylase release. VIP, however, with a rather low potency (EC50 at 155 nmol/l). Simultaneous stimulation with two compounds elicited additive responses, except for VIP and acetylcholine which elicited an effect significantly above additive response. Only SP, NKA, VIP and CGRP could be identified in extracts of the gland. The immunoreactivity of these peptides could be located to varicose nerve fibers in the gland. Binding of labeled SP to the isolated acini exhibited the characteristics of a genuine agonist/receptor interaction, and the rank order of displacement potencies indicated the presence of NK1-receptors. Thus, the results of the present study support previous suggestions that the tachykinins and VIP are likely to be involved in amylase secretion in the rat parotid gland.

[Ogilvie syndrome]. / Ogilvies syndrom.

Ogilvie's syndrome is a rare condition with progressive dilatation of the proximal colon without mechanical obstruction. Untreated it can lead to coecal perforation, peritonitis and death. It develops in patients with medical or surgical complications, but can be idiopathic. Caesarean section is the most common preceding surgical procedure. An imbalance between the parasympathetic and the sympathetic innervation of the intestine is thought to be the cause. Trauma to the retroperitoneum, infections, bleeding and electrolyte disturbances, hormonal changes and medicamina are predisposing factors. The syndrome can result in perforation of the coecum as early as the third or fourth day. Therefore a diagnostic abdominal X-ray should not be delayed by the intermittent presence of flatus and stool which is characteristic for this pseudo-obstructive condition. Medical treatment with neostigmine may be successful, coloscopic decompression of the colon is effective as is placing a tube in or close to coecum. If laparotomy is necessary, coecostomy has lower mortality than ileo-coecal resection.

[Ogilvie syndrome after Cesarean section]. / Ogilvies syndrom efter sectio.

INTRODUCTION: Ogilvie's syndrome, acute pseudo-obstruction of the colon, can lead to perforation of the caecum and death. The syndrome is not well known and diagnosis can be difficult to make in time. METHODS: We analysed seven cases of Ogilvie's syndrome with the aim of improving diagnostics. RESULTS: All had prolonged labour before cesarean section, which was complicated by bleeding. All were treated with syntocinon, a hormone that may influence gastrointestinal motility. All patients developed abdominal meteorism within a few days of operation, which increased despite the passing of flatus and stool. Five cases resulted in caecum perforation before the correct diagnosis and treatment were made. Perforation occurred on days 3-4, day 5, or probably days 8-10 after the operation. One of these patients, who suffered from severe adipositas, died. CONCLUSION: It is very important to make an early diagnosis, as the condition can progress quickly. Diagnosis should be made on the history, clinical assessment, and abdominal X-ray. Intermittent flatus and stool are characteristic of this truly non-obstructive condition and should not therefore delay a diagnostic X-ray.

Effect of pancreatic glucagon and its 1-21 fragment on gastric emptying in man.

The effect of pancreatic glucagon (G) and its 1-21 fragment (G 1-21) on gastric emptying was studied in nine healthy volunteers. Gastric emptying of a 200-ml nutrient liquid meal was assessed during continuous infusion of physiologic saline, G, or G 1-21 in equimolar concentrations. The subjects were studied three times on separate days in randomized order. Gastric emptying was measured with a gamma camera technique. The emptying was diphasic in all studies, showing an initial plateau lasting 10-15 min followed by an exponential decline. During saline infusion the time necessary for 50% of the meal to leave the stomach was 32 +/- 4 min, compared with 30 +/- 4 min and 35 +/- 3 min during infusion of G and G 1-21, respectively. It is concluded that glucagon and its 1-21 fragment in physiologic concentrations do not seem to participate in the control of gastric emptying of a nutrient liquid meal.

Stimulation of rainbow trout gallbladder contraction by cionin, an ancestral member of the CCK/gastrin family.

Cionin--from the protochordate Ciona intestinalis--is a putative ancestor of cholecystokinin (CCK) and gastrin. Being sulfated on tyrosine in positions 7 and 6 (from the C-terminus), characteristic for CCK and gastrin, respectively, cionin is a structural hybrid of the two peptides. The effects of cionin have previously been characterized in mammalian systems. This study examined a phylogenetically ancient CCK receptor, the rainbow trout (Oncorhynchus mykiss) gallbladder receptor, utilizing cionin, sulfated and nonsulfated CCK and gastrin, and the receptor antagonists L-364,718 and L-365,260. The sulfated peptides induced concentration-dependent contractions of isolated strips of gallbladder with equal efficacy and similar potencies [ED50: 42 (cionin), 23 (CCK-8-s), and 74 nM (gastrin-17-s)], significantly different from the nonsulfated forms [ED50: 1.7 (CCK-8-ns) and 1.9 microM (gastrin-17-ns)]. Ten micromolar L-364,718 and L-365,260 both weakly but significantly inhibited cionin-CCK-8-s, and gastrin-17-s-induced contractions. L-365,260 shifted the concentration response curves 1 1/2 decades to the right and L-364,718 only 1/2 decade. The results confirm that the rainbow trout gallbladder CCK receptor does not distinguish sulfated CCK from sulfated gastrin as do modern CCKA receptors, but does distinguish sulfated from nonsulfated forms of both. However, for optimal effect the receptor does not require a double-sulfated peptide like cionin as might be expected from the lack of selectively between CCK and gastrin. Finally, studies with antagonists known to be specific for either CCK or gastrin receptors in mammalian systems indicate that this ancient receptor behaves more like a mammalian CCKB receptor than as a CCKA receptor.

Jejunal diverticulosis in a family.

The presence of small intestinal diverticula was examined in a family of eight siblings. Six of the siblings had diverticula of the duodenum and/or the jejunoileal tract. Three of them had multiple jejunoileal diverticula, one had two jejunal diverticula, and two had duodenal diverticula. In addition, diseases of an immunologic nature were present in four of the siblings (rheumatoid arthritis, ulcerative colitis, myxoedema following thyroiditis, and non-viral hepatitis).

Affinity labeling the bovine gallbladder cholecystokinin receptor using a battery of probes.

Although the gallbladder was the first recognized target of the peptide hormone cholecystokinin (CCK) and is a physiologically important target, only one preliminary report of the biochemical characterization of this receptor exists. Recently, a series of molecular probes for the affinity labeling of different domains of the pancreatic CCK receptor have been developed. In this work we report the application of several of those probes toward the biochemical characterization of the bovine gallbladder muscularis receptor. These include "long" (125I-Bolton-Hunter-CCK-33) and "short" (125I-D-Tyr-Gly-[Nle28,31)CCK-(26-33)]) probes chemically cross-linkable through their amino-terminal amino groups and monofunctional probes with their photolabile moieties at their amino terminus (2-diazo-3,3,3-trifluoropropionyl-125I-D-Tyr-Gly-[(Nle28,31) CCK-(26-33)]) and carboxyl terminus (125I-D-Tyr-Gly-[(Nle28,31,pNO2-Phe33)CCK-(26-33)]), that span the receptor-binding region. Each of these bound specifically and saturably to a preparation enriched in plasma membranes from bovine gallbladder muscularis (mean inhibitor constants: 5.2, 1.1, 0.8, and 1.8 nM, respectively). A major relative molecular weight (Mr) 70,000-85,000 band was specifically and reproducibly labeled with the appropriate apparent affinity by each of the probes, whereas labeling of minor bands of Mr 40,000-50,000, Mr 92,000, Mr 120,000, and Mr 200,000 was dependent on cross-linker type or concentration. These observations support the identification of the Mr 70,000-85,000 protein as the bovine gallbladder CCK-binding subunit and, since this is a different size from the pancreatic CCK-binding subunit, provide biochemical evidence for molecular heterogeneity of peripheral CCK receptors.

Functional and biochemical characterization of the human gallbladder muscularis cholecystokinin receptor.

Gallbladders removed at cholecystectomy are a potentially useful source of human receptor for the gastrointestinal peptide hormone cholecystokinin (CCK). Seven healthy gallbladders (removed incidentally at time of resection of hepatic metastases) and 50 diseased gallbladders were studied. Cholecystokinin radioligand binding to an enriched plasma membrane preparation from these tissues was shown to be rapid, reversible, temperature-dependent, saturable, specific, and high-affinity. Computer analysis of equilibrium binding data using the Ligand program best fit a single class of binding sites with Kd = 1.0 +/- 0.1 nM (mean +/- SEM). This was similar in health and disease, with no apparent differences related to age, gender, or body habitus. The structural specificity for binding to this site correlated well with relative potencies for CCK-gastrin peptides to stimulate gallbladder contraction. To biochemically characterize this receptor, we used a battery of reagents, including "long" (125I-Bolton Hunter-CCK-33) and "short" 125I-D-Try-Gly-[(Nle28,31)CCK-26-33] probes that were cross-linkable through their amino terminus and a monofunctional probe with a photolabile group at its carboxyl terminus 125I-D-Tyr-Gly[(Nle28,31,pNO2-Phe33)CCK-26-33]. All probes specifically labeled a human gallbladder muscularis protein of Mr = 85,000-95,000, which was also independent of diagnosis. Labeling of this band was inhibited in a concentration-dependent manner by CCK-8 and by L-364,718. Thus, the CCK receptor present on the very common surgically removed human gallbladder is functionally and biochemically intact and is useful for further characterization.

Truncated GLP-1 (proglucagon 78-107-amide) inhibits gastric and pancreatic functions in man.

We studied the effect of intravenous infusion of synthetic truncated GLP-1 (proglucagon 78-107-amide) on fasting and postprandial gastric acid secretion, gastric emptying, and pancreatic secretion of trypsin and lipase in eight normal volunteers using marker dilution and aspiration technique. The infusion resulted in a plasma concentration of 110 +/- 14 pmol/liter (mean +/- SEM). Truncated GLP-1 significantly inhibited postprandial acid secretion by 43 +/- 11% in spite of unchanged plasma gastrin concentration. Gastric emptying rate decreased significantly; 50% emptying time increased from 16 +/- 2 min to 30 +/- 5 min. Postprandial trypsin and lipase outputs were significantly inhibited by 47 +/- 17% and 40 +/- 9% during truncated GLP-1 infusion. Pancreatic enzyme output was linearly correlated to gastric emptying, and truncated GLP-1 did not affect this relationship, suggesting that the effect on pancreatic secretion was secondary to the effect on gastric emptying. Postprandial insulin and glucagon concentrations were similar with and without truncated GLP-1 infusion in spite of significantly lower blood glucose levels (5.2 +/- 0.2 versus 3.7 +/- 0.3), indicating that GLP-1 stimulated insulin secretion and inhibited glucagon secretion. In conclusion, our results suggest that truncated GLP-1 act as a physiological inhibitor of gastric and pancreatic functions in man.

Cionin, a protochordean hybrid of cholecystokinin and gastrin: biological activity in mammalian systems.

The protochordean octapeptide cionin is structurally a hybrid of mammalian cholecystokinin (CCK) and gastrin, and thus their possible common ancestor. To determine whether cionin behaves like CCK or gastrin, we examined its effect on canine fundic somatostatin cells and on porcine and bovine gallbladder muscles. Cionin released somatostatin with a potency (ED50 0.15 nM) and efficacy (14.8% of cell content) similar to that of CCK-8 (ED50 0.12 nM, efficacy 16.7%). The efficacies but not the potencies of CCK-8 and cionin differed from those of sulfated gastrin (0.12 nM, 9.7%), nonsulfated gastrin (0.20 nM, 9.4%), and nonsulfated CCK-8 (0.30 nM, 10.4%). CCK and gastrin stimulated contractions of porcine gallbladder muscle strips in a concentration-dependent manner with no differences in efficacy but with characteristic differences in potency. CCK-8 and cionin displayed similar potencies of ED50 2.0 and 2.6 nM; both were significantly different from the ED50 of 0.4 microM for sulfated gastrin and 2.3 microM for nonsulfated gastrin. CCK radioligand binding to membrane-enriched preparations of porcine and bovine gallbladder muscularis was specific and of high affinity. The equilibrium data revealed that binding of CCK and gastrin peptides best fit a single site. CCK-8 and cionin displayed similar affinities [Kd 0.5 nM (porcine), 0.5 nM (bovine, CCK) vs. Kd 0.8 and 0.9 nM (cionin), respectively]. These differed again significantly from Kd 0.6 and 1.5 microM (sulfated gastrin) and 0.7 and 0.2 microM (nonsulfated gastrin). The results show that cionin behaves like CCK rather than gastrin in mammals.

Oxyntomodulin from distal gut. Role in regulation of gastric and pancreatic functions.

We studied the effects of intravenous infusion of synthetic oxyntomodulin (proglucagon 33-69), a potential hormone from the ileal mucosa, on fasting and postprandial gastric acid secretion, gastric emptying, gastroduodenal motility, and pancreatic secretion of trypsin and lipase measured simultaneously in six normal volunteers using multilumen tubes for infusion of markers, manometry, and aspiration of gastric and duodenal contents. The infusion resulted in plasma concentrations of 203 +/- 21 pmol/liter (mean +/- SEM) of oxyntomodulin, regarded as high but not unphysiological concentrations of the peptide. Oxyntomodulin almost abolished basal acid secretion and inhibited postprandial acid secretion by 35 +/- 10%. Gastric emptying decreased significantly; the time for 50% to leave the stomach increased from 17.3 +/- 2.2 min to 34.7 +/- 8.0 min. The postprandial gastroduodenal motility was massively inhibited by oxyntomodulin. Postprandial trypsin and lipase output was significantly inhibited by 56 +/- 12% and 42 +/- 11%, respectively, during oxyntomodulin infusion. However, pancreatic enzyme output was linearly related to gastric emptying and oxyntomodulin did not influence this relationship, suggesting that oxyntomodulins effect was due to its effect on gastric emptying. Oxyntomodulin seems to play an important role in the small intestinal inhibitory control of gastropancreatic functions.

Oxyntomodulin: a potential hormone from the distal gut. Pharmacokinetics and effects on gastric acid and insulin secretion in man.

Synthetic oxyntomodulin, a predicted product of the glucagon gene, which is produced in the human lower intestinal mucosa, was infused in doses of 100 and 400 ng kg-1 h-1 into six volunteers to study its pharmacokinetics and effects on pentagastrin-stimulated gastric acid secretion (100 ng kg-1 h-1). The concentration of oxyntomodulin in plasma measured with a cross-reacting glucagon assay increased from 37 +/- 5 to 106 +/- 17 and 301 +/- 40 pmol l-1, respectively. The metabolic clearance rate was 5.2 +/- 0.7 ml kg-1 min-1 and the half-life in plasma was 12 +/- 1 min. Oxyntomodulin reduced the pentagastrin-stimulated acid secretion by 20 +/- 9% during the low-rate infusion (P less than 0.05) and by 76 +/- 10% during the high-rate infusion (P less than 0.05). In accordance with the homology with glucagon, there was a small, significant rise in plasma concentrations of insulin and insulin C-peptide during oxyntomodulin infusion. Oxyntomodulin may therefore be included among the potential incretins and enterogastrones in man.

Gastrin-releasing peptide is a transmitter mediating porcine gallbladder contraction.

We studied the role of gastrin-releasing peptide (GRP) for porcine gallbladder motility. Immunohistochemistry visualized nerve fibers containing GRP-like immunoreactivity in muscularis. GRP concentration dependently stimulated contractions of muscularis strips (ED50, 2.9 nM). Neuromedin B was less potent (ED50, 0.1 microM), suggesting existence of GRP-preferring receptors. GRP-induced contractions were unaffected by muscarinic antagonism (1 microM atropine), axonal blockade (1 microM tetrodotoxin), cholecystokinin (CCK) receptor antagonism (10 microM MK-329), or substance P desensitization (1 microM), supporting the existence of myogenic GRP receptors. The bombesin (BN) analogue D-Phe6-BN-(6-13)propylamide (PA) stimulated contractions (ED50, 3.3 nM) with low efficacy (29% of that of GRP). D-Phe6-BN-(6-13)PA (1 microM) shifted GRP concentration-response curves one log to the right. D-Phe6-BN-(6-13)PA interacted specifically with GRP receptors; while abolishing responses to GRP (1 nM), responses to substance P (0.1 microM) and CCK-8 (1 nM) were unchanged. Electrical stimulation (10 Hz, 0.5 ms, 10 V) caused a rapid onset-slow offset, tetrodotoxin-sensitive excitation. Atropine reduced the amplitude to 58% and caused a delayed, slow onset-slow decline response. D-Phe6-BN-(6-13)PA reduced the amplitude to 59% and caused a very rapid onset-rapid decline response. Atropine plus D-Phe6-BN-(6-13)PA abolished responses to nerve stimulation. Nerve stimulation caused significant release of GRP-like immunoreactivity. Thus two neural inputs were defined: a cholinergic rapid onset-rapid offset excitation and a delayed, slow onset-slow offset excitation caused by release and subsequent binding of GRP to GRP-preferring receptors.

GLP-1 (glucagon-like peptide 1) and truncated GLP-1, fragments of human proglucagon, inhibit gastric acid secretion in humans.

Glucagon-like peptide 1 amide (GLP-1 amide), a predicted product of the glucagon gene (proglucagon 72-107-amide), and truncated GLP-1 (proglucagon 78-107-amide), recently isolated from porcine small intestine, were infused in doses of 100 and 400 ng/kg/hr and 12.5 and 50 ng/kg/hr, respectively, into eight volunteers to study pharmacokinetics and effects on pentagastrin-stimulated gastric acid secretion (plateau stimulation with pentagastrin at D50: 100 ng/kg/hr). The concentration of GLP-1 in plasma increased from 64 +/- 12 to 189 +/- 23 and 631 +/- 76 pmol/liter, respectively. The concentration of truncated GLP increased from approximately 7 pmol/liter to 28 +/- 3 pmol/liter during the high rate of infusion. A similar increase was seen in response to a mixed meal in eight normal volunteers. The metabolic clearance rate (MCR) of GLP-1 was 2.2 +/- 0.3 and 2.6 +/- 0.3 ml/kg/min, respectively, and the half-life in plasma was 17 +/- 2 min. The MCR of truncated GLP-1 was 13 +/- 2.8 ml/kg/min and the half-life 11.4 +/- 2.1 min. GLP-1 reduced the pentagastrin-stimulated acid secretion 16 +/- 9% during the low-rate infusion and 23 +/- 12% during the high rate (P less than 0.05). Truncated GLP-1 caused a 36 +/- 3% inhibition during the high infusion rate. Thus truncated GLP-1, a naturally occurring peptide, is a potent inhibitor of acid secretion in man and more so than GLP-1.

Bovine gallbladder muscularis: source of a myogenic receptor for cholecystokinin.

Despite being a classic target for the gastrointestinal peptide hormone, cholecystokinin (CCK), the gallbladder CCK receptor is not well characterized. Pharmacological studies of small species suggest that CCK action can be mediated by direct myogenic or by both myogenic and neurogenic receptors. To prepare for the biochemical characterization of a gallbladder CCK receptor and to define the subtype of the receptor being studied, we have performed autoradiographic localization and pharmacological characterization of CCK receptors on bovine gallbladder. Autoradiography demonstrated high-affinity specific CCK-binding sites only on the muscularis. CCK-8 stimulated tonic contraction of longitudinal strips of gallbladder muscularis in a concentration-dependent manner, with an ED50 of 0.2 nM. Antagonism at the cholinergic receptor with 1 microM atropine or axonal transmission with 1 microM tetrodotoxin did not modify CCK-induced contraction, supporting a direct myogenic effect of this hormone. Optimal electrical field stimulation (10 V, 10 Hz, 500 microseconds) to elicit a neuronal response resulted in muscle strip relaxation, which was abolished with adrenergic blockade (1 microM phentolamine, 1 microM propranolol). Although acetylcholine administration stimulated contraction, electrical field stimulation did not, even in the presence of phentolamine, propranolol, and/or CCK. Thus, in bovine gallbladder muscularis, there is evidence for a functional CCK receptor only on smooth muscle cells. Demonstration of a single, high-affinity specific CCK-binding site on an enriched plasma membrane preparation of bovine gallbladder muscularis is consistent with this representing a myogenic CCK receptor.