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Information concerning the cellular localization of cholecystokinin (CCK)-1 receptors has been discrepant and remained scanty at ultrastructural levels. The present immunohistochemical study at light and electron microscopic levels revealed the distinct localization of CCK1 receptors in visceral organs. Immunohistochemistry by use of a purified antibody against mouse CCK1 receptor was applied to fixed tissue sections of the pancreas, gallbladder, stomach, and intestine of mice. A silver-intensified immunogold method revealed the subcellular localization under electron microscope. The immunoreactivity for CCK1 receptors was selectively found in the basolateral membrane of pancreatic acinar cells and gastric chief cells but was absent in pancreatic islets and gastric D cells. Another intense expression in the gut was seen in the myenteric nerve plexus of the antro-duodenal region and some populations of c-Kit-expressing pacemaker cells in the duodenal musculature. The gallbladder contained smooth muscle fibers with an intense immunoreactivity of CCK1 receptors on cell surfaces. The restricted localization of CCK1 receptors on the basolateral membrane of pancreatic acinar cells and gastric chief cells, along with their absence in the islets of Langerhans and gastric D cells, provides definitive information concerning the regulatory mechanism by circulating CCK. Especially, the subcellular localization in the acinar cells completes the investigation for the detection of circulating CCK by the basolateral membrane. [ABSTRACT FROM AUTHOR]

Gastrin is important for stimulating acid secretion as well as differentiating gastric mucosal cells via cholecystokinin-2 receptors (CCK-2Rs). In turn, CCK acts preferably via CCK-1R to release somatostatin, and somatostatin has been postulated to exhibit a tonic inhibition of gastrin bioactivity. The present study was designed to examine the hypothesis that CCK-1R and 2R may act in opposite directions in gastric acid secretion. Having generated CCK-1R(−/−), 2R(−/−), and 1R(−/−)2R(−/−) mice, we examined the regulation of gastric acid secretion in four genotypes including wild-type mice. Parietal cells possess histamine receptors, muscarinic receptors, and CCK-2Rs. Since histamine increases cAMP and carbachol increases calcium, the responses of gastric acid secretion to graded doses of histamine, carbachol, and a combination of histamine + carbachol were determined. The sensitivity to histamine did not differ among the four genotypes, while the maximal acid secretion was lower in CCK-2R(−/−) mice than in wild-type mice. In addition, sensitivity to carbachol was impaired in mice without CCK-2R. The interaction of histamine and carbachol was conserved in all genotypes. In conclusion, CCK-2R is necessary to respond to carbachol as well as to produce the maximal acid secretion, while the role of CCK-1R in acid secretion is less important. [ABSTRACT FROM AUTHOR]

Gallbladder dysmotility accelerates cholelithiasis. In turn, gallbladder dysmotility can occur secondary to inflammation and excess cholesterol accumulation in gallbladder smooth muscle. The present study was designed to determine how much gallbladder dysmotility contributes to gallstone formation as a primary cause and whether a sex difference exists in gallstone formation by comparing cholecystokinin-1 receptor gene-deficient [CCK-1R(−/−)] male and female mice. No sludge or gallstone formation was observed in mice at 6 months of age. The frequency of sludge and gallstone formation in mice at 12 and 24 months of age was slightly higher in female CCK-1R(−/−) mice than in males, but the difference was not significant. Gallbladder dysmotility may have accelerated sludge and gallstone formation, but its contribution was limited. A 12-month period was required to produce gallstones, and after the mice reached 12 months of age, further ageing did not increase the frequency of gallstones. The effect of sex did not reach a significant level. [ABSTRACT FROM AUTHOR]

Background Methods. A liquid gastric load prepared with phenol red was administered via an orogastric tube (0.15 ml/mouse). The animals were killed by decapitation, and gastric emptying was estimated at 10 and 30 min after ingestion. The effects of the sulfated form of CCK-8 (CCK-8S) and of graded doses of atropine were examined. In addition, a proton pump inhibitor was administered to wild-type mice to examine the contribution of gastric acid to emptying. Results. Gastric emptying was significantly enhanced in mice lacking CCK-BR, as compared with wild-type and CCK-AR(-/-) mice. CCK-8S inhibited gastric emptying in mice with CCK-AR, but not in mice without CCK-AR. A proton pump inhibitor did not affect gastric emptying. Atropine dose dependently inhibited gastric emptying in all genotypes. The thickness of smooth muscle was comparable for all genotypes. Conclusions. The gastric emptying of a nonnutrient liquid load was enhanced in mice without CCK-BR, although the precise mechanism is not known. Although cholecystokinin (CCK) has been shown to inhibit gastric emptying via CCK-A receptors (CCK-ARs), the role of CCK-B receptors (CCK-BRs) has not been verified. We examined whether gastric emptying of a nonnutrient liquid load was modified in CCK-AR, BR, and ARBR gene knockout mice. [ABSTRACT FROM AUTHOR]

The etiology of gallstones is multifactorial, with interactions between genes and the environment. We generated cholecystokinin (CCK) -A receptor (R)-deficient (-/-) mice and found that CCK did not produce gallbladder contraction in CCK-AR(-/-) mice. The purpose of this study was to identify the role of CCK-AR on gallstone formation. Age-matched CCK-AR gene (+/+) and (-/-) progenies were used. Sludge and gallstone formation, as well as plasma cholesterol levels, were measured at 12 and 24 months of age. Sludge and gallstone formation were significantly higher in CCK-AR(-/-) mice than in CCK-AR(+/+) mice at 12 and 24 months of age, although these were not different between 12 and 24 months of age. The plasma cholesterol levels, daily food intake, and body weight were not significantly different between CCK-AR(+/+) and (-/-) mice. Sludge and gallstone formation were not observed at 6 months of age. In conclusion, deteriorated gallbladder contraction due to a lack of CCK-AR favored gallstone formation after the middle age of life. [ABSTRACT FROM AUTHOR]

Focuses on cholecystokinin (CCK) and CCK receptors. Physical mapping of CCK and gastrin genes; Regulation of CCK release; Molecular cloning of CCK-A and -B receptors.

Background. The etiology of gallstone formation is multifactorial, and genetic factors are involved. The genetic variations of cholecystokinin A receptor (CCKAR) in patients having gallstones and the molecular mechanisms of this polymorhpism were examined. The involvement of CCK-AR in gallstone formation was confirmed using CCK-AR gene knockout mice. Methods. CCK-AR gene expression was determined by Northern transfer analysis in gallbladders with or without gallstones. Genetic variations were determined by Southern blot and by direct sequencing. Molecular mechanisms in terms of the transcriptional activity and methylation status were examined. Finally, we investigated whether gallstone formation was enhanced in CCK-AR gene knockout mice. Results. The gene expression of CCK-AR was significantly decreased in gallbladders with gallstones compared to those without gallstones. No genetic variations were detected in the coding region, but two sequence variations were detected in the promoter region in gallstone patients. However, no significant differences were found for the promoter activities of polymorphic promoter constructs. In contrast, less methylation in the promoter region was related to substantial expression of the CCK-AR gene. Gallstone formation was enhanced in CCK-AR gene knockout mice. The homozygote (GG/ TT) polymorphism of the CCK-AR gene showed a significantly higher percentage of body fat. Conclusions. Deteriorating gallbladder contractions, possibly induced by alterations in the CCK-AR gene, as well as CCK-AR gene polymorphism, promoted gallstone formation. [ABSTRACT FROM AUTHOR]

Background. We have previously shown that polymorphism in the promoter region of the human cholecystokinin type-A receptor (CCKAR) gene is a genetic factor affecting obesity. However, there have not yet been any reports of analysis of the promoter activity of CCKAR genes, and thus almost nothing is known about CCKAR transcriptional regulation. Methods. Using STC-1 cells, an enteroendocrine tumor cell line, we measured the promoter activity of the human CCKAR gene by a transient transfection method. Results. We showed that STC-1 cells expressed CCKAR as well as its peptideligand, CCK. Analysis of a series of 5'-deleted promoter constructs showed that the proximal 622-base region upstream from the initiation site, which contained two GC-box motifs, was important as a regulatory region for the transcriptional activity. However, no significant differences were found for the promoter activities of polymorphic promoter constructs. Conclusions. These results suggest that the reported polymorphism may not play a role in transcriptional regulation. Background. We have previously shown that polymorphism in the promoter region of the human cholecystokinin type-A receptor (CCKAR) gene is a genetic factor affecting obesity. However, there have not yet been any reports of analysis of the promoter activity of CCKAR genes, and thus almost nothing is known about CCKAR transcriptional regulation. Methods. Using STC-1 cells, an enteroendocrine tumor cell line, we measured the promoter activity of the human CCKAR gene by a transient transfection method. Results. We showed that STC-1 cells expressed CCKAR as well as its peptideligand, CCK. Analysis of a series of 5'-deleted promoter constructs showed that the proximal 622-base region upstream from the initiation site, which contained two GC-box motifs, was important as a regulatory region for the transcriptional activity. However, no significant differences were found for the promoter activities of polymorphic promoter constructs.... [ABSTRACT FROM AUTHOR]

The effects of the intraduodenal administration of a low dose of CR-1505 for 3-7 days on the gene expression of cholecystokinin (CCK), plasma CCK concentration, and CCK content in the intestinal mucosa were examined in rats. The simultaneous changes of protein and enzyme content in the pancreas were also determined. CR-1505 was infused continuously into the duodenum at a dose of 3 mg/kg per day, calculated to correspond to a dose of 150-200 mg/day in humans. Seven days after the administration of CR-1505, a liquid meal (4.5 kcal/3 ml) was introduced into the stomach and changes in the intestinal CCK content and plasma CCK concentration were examined. The level of CCK mRNA in the intestine was significantly higher in rats treated with CR-1505 than in control rats. The plasma CCK concentration, the CCK content of the intestinal mucosa, and the composition of pancreatic enzymes did not significantly differ in rats treated with CR-1505 and the untreated controls. In control rats, the administration of the liquid meal increased the plasma CCK concentration and significantly decreased the intestinal CCK content in water extracts, but did not affect the amount extracts in acid whereas the ingestion of the meal did not cause any significant changes in rats treated with CR-1505. These findings indicate that a low dose of CR-1505 stimulates the gene expression of CCK without enhancing CCK release or exerting an effect on the pancreas. [ABSTRACT FROM AUTHOR]

Cholecystokinin, a brain gut peptide that stimulates gall bladder contraction and pancreatic exocrine secretion, also acts as a neurotransmitter. In this study, we demonstrated that small amounts of cholecystokinin precursor mRNA were expressed in the heart, lung, and kidney, as well as in the brain and the small intestine. The nucleotide sequences of the coding regions of the cholecystokinin precursor mRNA in these tissues were identical to those of the small intestine, indicating that cholecystokinin precursor proteins produced in these tissues are identical to those in small intestine. This is the first report demonstrating that the cholecystokinin precursor gene is expressed in the heart, lung, and kidney, as well as in the gastrointestinal tract and brain. [ABSTRACT FROM AUTHOR]

Pancreatic exocrine secretion in the conscious rat is regulated by proteases in the intestine secreted by the pancreas, and cholecystokinin (CCK) is known to be involved in the mechanism. The authors proposed that the release of CCK was regulated by a CCK-releasing factor secreted into the intestinal lumen from the proximal intestine. We isolated and partially purified a CCK-releasing factor from rat small intestine by gel filtration and high performance liquid chromatography. The partially purified CCK-releasing factor increased pancreatic exocrine secretions and plasma CCK concentrations in conscious rats and this activity was abolished after the incubation with trypsin. The bioactivity of the partially purified CCK-releasing factor was confirmed. [ABSTRACT FROM AUTHOR]

The effect of somatostatin (SS) on the pancreatic enzyme secretion was studied in a perfusion system using dispersed pancreatic rat acini in vitro. In addition the effect of SS on pancreatic secretion in vivo was also studied in conscious rats for comparison. In an in vitro study, 6×10M SS-14 caused no significant change in amylase release when added 20 min before stimulation by 10M carbamylcholine (Cch), 10M A23187, 5×10M secretin and 2mM dibutyryl cyclic AMP. The addition of 6×10M SS-28 also caused no significant change in amylase release stimulated by 10M Cch. High performance liquid chromatographic examination indicated that no degradation of either SS-14 or SS-28 occurred after reaction with dispersed acini. In an in vivo study SS-14 caused marked inhibition of basal pancreatic secretion and stimulated pancreatic secretion by bile-pancreatic juice diversion. These results indicate that SS has no direct inhibitory action on rat pancreatic secretion, and that SS may inhibit the pancreatic secretion by indirect mechanisms. [ABSTRACT FROM AUTHOR]

Exocrine pancreatic secretion to intravenous injections of a new stimulant of gastrointestinal motility, R51 619 (cisapride) was studied in conscious rats, and in the isolated pancreatic acini in vitro. The injection of cisapride (2 mg/kg) significantly increased fluid, bicarbonate and protein output in vivo. Atropine completely abolished the pancreatic responses to cisapride, and CR 1409, a new glutaramic acid derivative and a competitive cholecystokinin (CCK) inhibitor, tended to decrease the cisapride-induced pancreatic exocrine secretion. However, amylase release and Ca efflux from the isolated pancreatic acini were not stimulated. These results suggest that cisapride indirectly affects the pancreatic exocrine secretion primarily by releasing acethycholine from the intrapancreatic nerve endings and in part by releasing CCK from the duodenum, but has no direct action on the pancreas. [ABSTRACT FROM AUTHOR]

Conclusion: When taurocholate was injected into the common bile duct, high ductal pressure due to ligation of the pancreatic duct did not produce more damage in the pancreas of both old rats and young adult rats, and levels of pancreatic enzymes in portal venous effluent were lower in old rats than in younger rats Background: The effects of ligation of the pancreatic, duct and aging on acute pancreatitis caused by taurocholate are still unclear. Methods: Young adult and old male Wistar rats were used. Six hours after ligation of the common bile duct in both the duodenum and liver hilus, rats were killed and the pancreata were perfused. Taurocholate or normal saline was injected retrogradely into the common bile duct. The levels of amylase and lipase in the portal venous effluent were determined as markers of damage to the pancreas. The pancreas was also histologically examined after the perfusion experiments using an Image Analysis System. Results: (1) A nonsignificant elevation of pancreatic enzymes was found in portal venous effluent by the retrograde injection of saline into the common bile duct. Injection of taurocholate caused a marked elevation of enzymes in the effluent for the first 30 min after injection, which then gradually decreased. (2) Basal levels of pancreatic enzymes were significantly higher in the ligation group than in the nonligation group. Injection of saline into the common bile duct had no apparent effect on enzymes in the effluent. In contrast, taurocholate injection into the common bile duct produced a marked increase in enzymes in the portal venous effluent. However, no significant difference was found between the ligation group and the nonligation group. (3) Similar findings were obtained when old rats were used. (4) Although basal levels of enzymes were almost the same in nonligated old and young adult rats, taurocholate injection into the pancreatic duct in old rats resulted in a significant depression of enzymes compared to that in young adult rats. In the ligation group, pancreatic enzymes in the portal venous effluent following taurocholate injection tended to be lower in old rats than in young adult rats. The results were histologically supported in that various degrees of fibrosis were found in the pancreata of old rats. [ABSTRACT FROM AUTHOR]

The effects of a newly synthesized peptide, human gastrin-releasing peptide (hGRP), on the pancreatic exocrine secretion and the release of pancreatic polypeptide (PP) were examined in the conscious rat. Plasma PP concentrations were determined by a recently established specific radioimmunoassay for rat PP. Amounts of 0.18, 0.35, and 3.5 nmol/kg/h hGRP significantly stimulated both pancreatic exocrine secretion and 0.35 nmol/ kg/h of hGRP increased PP release. Simultaneously infused proglumide (300 mg/kg/h) did not affect either pancreatic exocrine secretion or PP release. However, simultaneous infusion of atropine (100 μg/kg/h) slightly inhibited PP release, but did not restrict the incremental response of pancreatic protein secretion to hGRP. These results suggest that hGRP directly stimulates pancreatic exocrine secretion and PP release. [ABSTRACT FROM AUTHOR]

Changes in pancreatic exocrine functions were compared between conscious rats with bile duct ligation and bile diversion from the duodenum on the first, third, fifth, and seventh postoperative days. Body weight was significantly decreased with time in both groups. Basal secretions of fluid, bicarbonate, and protein remained unchanged throughout the experimental period in bile duct ligated rats, whereas in bile diverted rats, the basal bicarbonate secretion with returning of pancreatic juice to the duodenum increased on the third postoperative day, and the basal protein output significantly increased with time. Basal secretions with returning of pancreatic juice to the duodenum in both groups were higher than that in control (bile and pancreatic juice returned to the intestine) rats. Stepwise increases in fluid and bicarbonate outputs responding to the graded doses of secretin were observed in bile duct ligated rats on the first and third postoperative days, as has been observed in bile diverted rats. However, on the fifth and seventh postoperative days, stepwise responses to graded doses of secretin were no longer observed in bile duct ligated rats. The pancreatic response to cerulein was greater in bile diverted rats than in bile duct ligated rats. Plasma CCK concentration in 7-d bile duct ligated rats (4.7 pM) was significantly higher than that in 7-d bile diverted rats (1.6 pM), although the pancreatic wet weight, protein concentration, and total content were comparable for the two groups. It was suggested that the presence of bile in the duodenum is required to maintain normal pancreatic secretion, and that the removal of bile from the intestine has quite different effects, depending on whether the bile flow is obstructed or diverted. [ABSTRACT FROM AUTHOR]

Serial changes in the levels of cholecystokinin (CCK)-A receptor mRNA in the pancreas after pancreatic duct occlusion were examined in rats. CCK-A receptor mRNA level was determined by Northern blot analysis with a rat CCK-A-receptor cDNA probe. The level of CCK-A receptor mRNA first decreased, reaching the lowest level 7 days after occlusion, and then began to increase. On day 14, it had completely recovered to the control level and it remained at that level until 28 days after occlusion. [ABSTRACT FROM AUTHOR]

The effects of a new cholecystokinin (CCK) antagonist (FK 480; 0.1 mg/kg per day given by intragastric administration to rats for 3 days) on the expression of the CCK and secretin genes, plasma CCK immunoreactivity, and CCK content in the intestinal mucosa were examined. FK 480 increased the level of CCK mRNA in the intestine to 1.7 times the level in control rats, but did not affect the level of secretin mRNA. It did not increase plasma CCK immunoreactivity or CCK content in the intestinal mucosa. These results suggest that the ingested FK 480 directly increased CCK mRNA level in the intestine and produced a dissociation between the synthesis and release of CCK. [ABSTRACT FROM AUTHOR]