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Background: Alcoholic beverages stimulate gastric acid secretion and increase the appetite. Although ingested ethanol stimulates pancreatic secretion, alcoholic beverages contain several congeners. N‐methyltyramine (NMT) was isolated from beer as a factor in stimulating gastric acid secretion. In this study, we examined NMT to determine whether the congener stimulated pancreatic secretion in conscious rats.

Since the isolation and sequencing of cholecystokinin (CCK), considerable advances have been made in understanding the roles played by this peptide as a hormone and as a neuropeptide. CCK-1(A) and 2(B) receptor (R) cDNAs have been cloned; shortly thereafter, the naturally occurring CCK-1R gene-deficient rat (the Otsuka Long-Evans Tokushima Fatty (OLETF) rat) was discovered. This strain develops adult-onset diabetes with obesity, and has a 6847 base-pair deletion of the CCK-1R gene in which the promoter lesion and the first two exons are missing. At the same time, the genomic structures of CCK-1R in rats, mice, and humans were clarified. The CCK-1R gene consists of five exons interrupted by four introns. It has been determined that there is species- and tissue-specific CCK receptor heterogeneity of expression; in particular, there is evidence that the human pancreas does not express CCK-1R, while the pancreas in rodents primarily expresses CCK-1R. Although CCK-1R polymorphisms with amino acid changes such as 21Gly to Arg, 71 Arg to Gly, and 364 Val to Ile were discovered in subjects with obesity and diabetes mellitus, these changes occur sporadically. We identified two sequence changes, a G to T change in nucleotide - 128, and an A to G change in nucleotide - 81, in the promoter region of the CCK-1R gene. This polymorphism is considered to be a single nucleotide polymorphism (SNP) related to weight control difficulties in obese subjects as well as to psychiatric disorders. The precise molecular mechanisms of this polymorphism remain to be clarified.

SH-2 containing inositol 5-phosphatase 2 (SHIP2) is a family of inositol 5-phosphatases, which possess the 5-phosphatase activity that hydrolyzes phosphatidylinositol-3, 4, 5-trisphosphate to phosphatidylinositol-3, 4-bisphosphate and is suspected to negatively regulates the metabolic signaling of insulin. To clarify the possible involvement of SHIP2 in physiological abnormalities, we examined the human SHIP2 gene polymorphism in a Japanese cohort.

Alcohol abuse causes pancreatic damage in humans. However, only 5% of alcoholic patients have a clinical manifestation of pancreatitis, and the genetic predisposition of alcohol-associated pancreatitis remains elusive. Nonoxidative metabolites of ethanol, fatty acid ethyl esters (FAEEs), might play an important role in pancreatic damage. Carboxylester lipase (CEL) has been known to catalyze FAEE synthesis from fatty acids and ethanol.

Most of the acetaldehyde, a recognized animal carcinogen, generated during alcohol metabolism is eliminated by liver mitochondrial aldehyde dehydrogenase 2 (ALDH2). More than 40% of Japanese have the inactive form of ALDH2, and inactive ALDH2 is a risk factor for multiple cancers of the esophagus as well as head and neck cancer. Possible associations between pancreatic cancer and ALDH2 gene polymorphism, in conjunction with smoking and/or drinking habits, were examined in a Japanese population.

Although many studies have investigated the acute effect of ethanol on the rat pancreas, the effect of intravenous injection of ethanol on pancreatic secretion has been controversial. The purposes of this study were to examine whether intraduodenal and intravenous administration of ethanol stimulates pancreatic secretion in Wistar rats. To elucidate the mechanism, we examined whether ethanol influences pancreatic secretion in CCK-A receptor-deficient rats.

We investigated the relationship of polymorphisms in the cholecystokinin 1 receptor[CCK1R; Gto T(n‐128), Ato G(n‐81)] and the β3‐adrenergic receptor(β3‐AR; Trp64Arg) with midlife weight gain. The participants were 1012 Japanese men and women (40 to 59 years of age). Their weight at 18 years old was obtained from a questionnaire. Weight change was defined as the current weight minus the weight at 18 years old. Subjects were grouped into four categories by these genotypes: W/W = noncarriers, W/H = Arg64carriers of the β3‐AR, H/W = T(n‐128) or G(n‐81) carriers of the CCK1R, H/H = T(n‐128) or G(n‐81) and Arg64carriers. In men, the interaction between the CCK1Rand β3‐ARpolymorphisms was significant (two‐way ANOVA, p< 0.05), but neither the CCK1Rnor the β3‐ARwas individually associated with weight gain. The H/H group showed a higher possibility of weight gain of 10 kg or more compared with the W/W group in men. The odds ratio for weight gain (≥10 kg) of H/H was 2.54 (95% confidence interval: 1.50 to 4.30) compared with W/W. In women, neither main effect nor interaction was significant. These results suggest that the combination of CCK1Rand the β3‐ARpolymorphisms is a contributing factor for midlife weight gain in men.

There are many experimental models for chronic pancreatitis. However, it remains unclear which animal models of pancreatic fibrosis can be categorized as chronic pancreatitis models. We compared the histologic features of some animal models of pancreatic fibrosis/chronic pancreatitis and chronic pancreatitis in humans.

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.

Pancreatic exocrine function and bile secretion were examined in cholecystokinin (CCK)-B receptor gene-targeted mice and compared among different genotypes [i.e., CCK-B receptor gene: (/), wild-type; (/−), heterozygous; and (−/−), homozygous deficient]. The histology and protein concentrations in the pancreas also were examined. Amylase release from the dispersed acini was examined in vitro by using the various doses of CCK-8, carbachol, and secretin. In vivo, the bile and pancreatic juice were collected, and the concentrations of amylase and bile acid were measured in anesthetized mice. The responses to CCK (100 pmol/kg) or acetyl-β-methylcholine (500 nmol/kg) were examined. In vitro studies showed that the maximal effective concentrations of CCK-8 (10−10M), carbachol (10−5M), and secretin (10−7M), were comparable for all genotypes. Fluid, amylase, and bile acid outputs in vivo also were comparable for all genotypes. Pancreatic wet weight and protein concentrations were not significantly different, and no abnormal findings were observed on histologic examination in any genotype. These results indicated that the CCK-B receptor has no role in pancreatic growth, exocrine secretion, or bile secretion in adult mice.

Cholecystokinin stimulates pancreatic amylase secretion, gallbladder contraction, and pancreatic growth, etc. by binding with high affinity to a cholecystokinin type A receptor (CCKAR). To better understand the expression of CCKAR mRNA in terms of tissue specificity and postnatal development, we determined the methylation status of BssHII sites (5′-B sites) in the rat CCKAR gene promoter. The 5′-B sites in adult pancreas expressing CCKAR mRNA were much less extensively methylated than those in fetal pancreas not expressing the mRNA. In brain, liver, and kidney of adult rats not expressing CCKAR mRNA, the 5′-B sites were methylated. In pancreas, the demethylation level of the sites increased at 21 days after birth. Concomitant with the DNA demethylation level in the 5′-B sites, the mRNA level rose rapidly in 21 days. These results demonstrate that methylation and expression of the CCKAR gene reveal a good inverse correlation.

Whether cholecystokinin (CCK) has a direct action on duct cells and the role of CCK-A receptor in bicarbonate secretion were examined by comparing the results obtained from OLETF (CCK-A receptor-deficient rats) and control (LETO) rats. Rats were prepared with cannulae for draining bile and pancreatic juice separately, with two duodenal cannulae and an external jugular vein cannula. The experiments were conducted without anesthesia. The responses of bicarbonate secretion to intravenous infusion of CCK, acetyl-ß-methylcholine (Ach), and 2-deoxy-D-glucose (2DG), and to intraduodenal infusion of HCI and a liquid meal were examined. To examine the synergistic effect between CCK and secretin, the effect of CCK during a background secretin infusion was examined in LETO rats. CCK did not stimulate bicarbonate secretion in either strain, nor in LETO rats with secretin infusion. When gastric acid secretion was prevented by administration of omeprazole, Ach did not increase bicarbonate secretion, but 2DG did in both strains. Intraduodenal infusion of HCI and a liquid meal significantly increased bicarbonate secretion in both strains; however, the responses were much less in OLETF than LETO rats. In conclusion, intravenous injection of CCK did not stimulate bicarbonate secretion, and the lack of CCK-A receptor decreased bicarbonate secretion in response to luminal stimulants.

We summarize the discovery of luminal feedback regulation of pancreatic secretion in rats and its history. In rats, removal of proteolytic activity from the intestine produced a significant increase in pancreatic protein (enzyme) output. This increase was confirmed to be mediated by circulating chole-cystokinin (CCK). Subsequently, two CCK-releasing peptides, monitor peptide and luminal CCK-releasing factor (LCRF), were purified from the rat pancreatic juice and small intestine, respectively, to elicit CCK release in luminal feedback regulation. Furthermore, we emphasize the important physiologic roles of CCK and CCK receptors by the discovery of disrupted CCK-A-receptor gene in rats. These findings should help to determine the regulation of pancreatic secretion and CCK functions in humans.

We examined the role of the cholecystokinin-A (CCK-A) receptor in acute inflammatory and regenerative stages of experimental pancreatitis using a rat model lacking the CCK-A receptor [Otsuka Long-Evans Tokushima Fatty (OLETF) rats]. OLETF and control [Long-Evans Tokushima Otsuka (LETO)] rats were prepared with an internal bile fistula and with obstruction of pancreatic flow and were sacrificed 1-14 days later. Histological examination was performed, and changes in pancreatic wet weight, protein concentration, CCK-A and -B receptor mRNA levels, tyrosine kinase activities, and plasma amylase and CCK levels were determined. The plasma amylase level showed a transient increase on day I, the CCK level remained at high levels throughout, and tyrosine kinase activity was increased significantly on day 3 but declined thereafter. These parameters were comparable for both strains during the acute inflammatory stage. However, no regenerative findings were observed by histological examination and the protein concentration in the pancreas was significantly lower in OLETF rats on days 7-14, during which time regeneration was completed in LETO rats. These observations indicate that the absence of the CCK-A receptor did not modify the acute phase of pancreatitis but significantly retarded regeneration of the pancreatic tissue.

Changes in content and recovery of pancreatic enzymes after a protein-free diet were examined in young (8-month) and old (26-month) Fischer- 344female rats. In control rats fed a normal diet for 15 days, no significant difference between young and old rats was observed in pancreatic weight or in pancreatic content of protein, enzymes, and DNA. A 7-day protein-free diet significantly decreased pancreatic wet weight as well as content of protein, chymotrypsin, amylase, and DNA in both age groups, whereas body weight and amount of daily food intake did not differ from respective control values (in normal diet-fed rats) in either age group. In young rats, chymotrypsin and protein contents were significantly greater than control values during the recovery period in which rats were fed a normal diet following the 7-day protein-free treatment. In contrast, these values in old rats remained lower than corresponding control values throughout the entire recovery period. These results agree with our previous study suggesting that aging probably attenuates the reserve capacity of the pancreas for enzyme secretion, but not its basal functions.

Pancreatic duct occlusion is known to produce a sustained increase in the plasma cholecystokinin (CCK) concentration and to affect the tissue content of CCK in the rat. The tissue content of CCK is correlated with regenerative changes in the pancreas after pancreatic duct occlusion. In the present study, we examined the changes in mRNA levels of pancreatic secretory trypsin inhibitors (PSTIs), pancreatitis-associated protein (PAP), and amylase in the pancreas in comparison with changes in CCK and secretin mRNA levels in the intestine and the histological changes produced by pancreatic duct ligation. Rats with an internal bile fistula and with obstruction of pancreatic flow were prepared and were sacrificed 1, 3, 7, 10, 14, and 28 days later. Then mRNA levels of CCK, secretin, PSTIs, PAP, and amylase were determined by slot-blot analysis. The CCK mRNA level gradually increased to a peak on day 10, was slightly lower on day 14, and returned to the control level on day 28. The level of secretin mRNA did not change. The mRNA levels of PSTIs increased significantly on day 3 after occlusion. PAP mRNA was detectable on days 1 and 3, being maximal on day 1. The mRNA level of amylase was markedly decreased on days 1 and 3, then remained lower than the control level. Histological examination showed acute inflammatory changes in the pancreas on days 1 and 3 and regenerative changes from day 7. These results suggest that a change in gene expression of PAP reflects acute inflammatory changes in the pancreas most sensitively.

The effects of intraluminal bile on cholecystokinin release and pancreatic exocrine secretion were studied in conscious rats. Since it has been suggested that bile acid may influence pancreatic secretion indirectly by interacting with luminal protease activities, intraduodenal protease activities were eliminated by pancreatic juice diversion accompanied with simultaneous intraduodenal infusion of aprotinin. This treatment resulted in gradual increases in pancreatic juice flow, bicarbonate and protein outputs, and an increase in plasma cholecystokinin levels, reaching plateau levels 2 hr after the start of the treatment. When endogenous bile was excluded from the intestine, the pancreatic secretion and plasma cholecystokinin concentrations further increased. The intraduodenal infusion of sodium taurocholate during bile pancreatic juice diversion inhibited cholecystokinin release, while pancreatic protein output was only transiently decreased. The results indicate that bile in the duodenum directly regulates cholecystokinin release, probably through its major components, bile salts.

The possibility of the involvement of pancreatic polypeptide (PP) release in luminal feedback regulation in the conscious rat was examined. Pancreatic secretion in the intestinal phase in the rat is regulated by negative feedback control so that a decrease in luminal protease activities produced by a diversion of bile-pancreatic juice (BPJ) from the intestine stimulates pancreatic secretion. Plasma concentration of rat PP and the effect of exogenous infusion of rat PP on pancreatic secretions during BPJ diversion were determined. Plasma PP concentration significantly increased with BPJ diversion and peaked at 90 min after BPJ diversion began, almost paralleling changes in protein output. Exogenous PP infusion (1, 2, and 10 ?g/kg/hr) inhibited pancreatic protein and fluid outputs but not the bicarbonate output during BPJ diversion. PP was shown to be physiologically released in the intestinal phase of pancreatic secretion; however, the physiological role of endogenous PP remains unknown.

The plasma concentrations of pancreastatin and cholescystokinin (CCK), exocrine pancreatic responses, and gallbladder contraction following intrajejunal ingestion of 100 kcallhr semidigested liquid meal (Clinimeal) were simultaneously studied in six controls and six patients with chronic pancreatitis. An intrajejunal infusion of Clinimeal resulted in significant rises of pancreastatin and CCK, which paralleled the pancreatic secretion and gallbladder contraction. On the other hand, an intrajejunal infusion of Clinimeal resulted in a delayed rise of pancreastatin and no rise of CCK in chronic pancreatitis. Pancreatic secretion did not increase, and gallbladder contraction was not induced in these patients. It is suggested that pancreastatin may play an important role in the regulation of intestinal phase of exocrine pancreas. The impaired pancreastatin and CCK release in chronic pancreatitis may be due to the inappropriate stimuli in the lumen, which is attributed to pancreatic exocrine dysfunction, or to disturbed physiological regulation between the pancreas and gastrointestinal tract.

Pancreatic exocrine secretion in conscious rats is regulated by intraluminal bile and/or pancreatic juice. Exclusion of bile and/or pancreatic juice from the intestinal lumen caused cholecystokinin (CCK) release and stimulated pancreatic secretion. CCK in the plasma is mainly derived from endocrine cells in the proximal small intestinal mucosa. We examined the changes in CCK concentrations in the intestinal mucosa and compared them to those of plasma CCK concentrations and the changes of luminal trypsin activities after bile and/or pancreatic juice diversion in conscious rats. Rats with bile and pancreatic fistulae were used. Each treatment of bile, pancreatic juice, and bile-pancreatic juice diversion decreased luminal trypsin activity and increased plasma and intestinal CCK concentrations. The potency of the stimulatory effect on plasma and intestinal CCK concentrations was bilepancreatic juice diversion>pancreatic juice diversion?bile diversion. Neither plasma CCK concentration nor intestinal CCK concentration was in inverse proportion to trypsin activity. The plasma CCK concentration did not parallel intestinal CCK concentration. Intravenous infusion of CCK-8 (300 pmol/kg/hr) did not increase CCK concentration in the intestinal mucosa. It was proposed that bile and/or pancreatic juice in the intestinal lumen regulated CCK concentrations not only in the plasma but also in the intestinal mucosa.

In conscious rats, bile inhibits pancreatic secretion. The role of luminal taurocholate (TC), a major component of rat bile, in the regulation of pancreatic secretion was studied in conscious rats with external bile and pancreatic fistulae. On the fourth postoperative day, after the basal collection of bile and pancreatic juice (PJ) returned to the duodenum, graded doses of TC (0, 0.4, 4, 40 mM) containing 10 mM CaCl2 were infused into the duodenum instead of bile and PJ for 2 hr (1 ml/hr), with or without 1 mg/ml of porcine trypsin. Luminal trypsin activities were not affected by any dose of TC. The increases in pancreatic secretion in response to diversion of bile and PJ were progressively inhibited with increasing doses of infused TC from 0 mM to 4 mM both with and without trypsin infusion. The effects with 4 and 40 mM TC were not significantly different. Changes in plasma cholecystokinin concentrations roughly correlated with changes in protein output in rats without trypsin infusion. We concluded that TC directly inhibited pancreatic secretion independent of the luminal trypsin activity and that its inhibitory action was concentration dependent.

This study extends a recent observation that Otsuka Long-Evans Tokushima Fatty (OLETF) rats show no expression of the cholecystokinin (CCK)-A receptor gene in the pancreas because of a genetic abnormality. We compared the changes in pancreatic regeneration in terms of wet weight and protein and DNA contents after partial pancreatectomy (30 resection) in OLETF and control (Long-Evans Tokushima Otsuka; LETO) rats and examined whether the CCK-B receptor has a role in pancreatic regeneration after pancreatectomy. The pancreatic wet weight increased significantly with age in both OLETF and LETO rats regardless of surgical procedure, but the increase with respect to time was significantly less in OLETF than in LETO rats. The protein and DNA concentrations in the pancreas (mg/g wet tissue) were comparable for both strains after sham operation. However, they were significantly lower than pancreatectomy in OLETF rats compared to those after sham operation, whereas they were comparable in LETO rats regardless of surgical procedure. The ratio of protein content/DNA content (cell size) was significantly lower in OLETF than LETO rats under all conditions. CCK-B receptor gene expression was not enhanced after pancreatectomy. In conclusion, the CCK-A receptor is not an absolute requirement for pancreatic normal growth but is important for pancreatic regeneration.

In a previous study, we reported that the pancreatic wet weight in Otsuka Long-Evans Tokushima Fatty (OLETF) rats, cholecystokinin-A (CCK-A) receptor-defective because of a congenital gene abnormality, was significantly lower than in control rats (Long-Evans Tokushima Otsuka; LETO) from 3 weeks of age. In this study we examined apoptosis of pancreatic acinar cells in OLETF rats at 5 to 6 weeks of age in comparison with that in LET0 rats. We present here direct morphologic evidence of apoptosis in OLETF rats, using a 3′-OH nick end-labeling method for detecting cells with DNAstrand breaks and electron microscopy. Nick end-labeling revealed a sinall number of positively labeled acinar cells in OLETF rats. On electron microscopic examination, small numbers of apoptotic cells were seen in the lobules in OLETF rats but not in LETO rats. These results suggest that apoptosis plays an important role in the destruction of acinar cells of OLETF rats and induces atrophy of the pancreas.

This work extends a recent observation that Otsuka Long-Evans Tokushima Fatty (OLETF) rats, which have been established as an animal model of non-insulin-dependent diabetes mellitus, show no expression of the cholecystokinin (CCK)-A receptor gene in the pancreas. The CCK-A receptor is known to be involved in regulating pancreatic exocrine function and growth. We examined the growth of the pancreas in terms of wet weight, enzyme compositions, and protein and DNA contents at 5–6 and 24–25 weeks of age in OLETF rats and control (Long-Evans Tokushima; LETO) rats. The pancreatic wet weight increased significantly with age in both OLETF and LETO rats but was significantly lower in OLETF rats than in LETO rats. The total DNA contents in the whole pancreas (cell numbers) were comparable for both strains and increased significantly with age. However, the ratio of protein content to DNA content (the cell size) significantly increased with age in LETO rats. with no increase in OLETF rats. The changes in chymotrypsin, amylase, and insulin with respect to age were in the same direction in both strains: a decrease or no change in total and/or cellular contents of chymotrypsin and insulin and increases in amylase. These results suggest that the CCK-A receptor plays some role in the increase in cell size associated with normal growth of the pancreas from 5 to 25 weeks of age (after weaning).

Cholecystokinin (CCK) has been suggested to modulate insulin output. We have shown that Otsuka Long-Evans Tokushima Fatty (OLETF) rats show little or no expression of the CCK-A receptor gene in the pancreas. We examined whether the CCK-A and CCK-B receptor genes are expressed in the islets and the role of CCK-A receptor in insulin secretion. Gene expressions of CCK receptors were determined by the reverse-transcriptase polymerase chain reaction (RT-PCR) followed by Southern blot hybridization and Northern transfer analysis using LETO rats as controls. Pancreatic endocrine function was examined in perfusion (exogenous CCK stimulation) and meal ingestion (endogenous CCK stimulation) studies. CCK-A receptor mRNA was detected in the islets of LETO rats but not OLETF rats. Expression of the CCK-B receptor gene was detected in both strains by RT-PCR. Insulin secretion was impaired in OLETF rats, but the insulin contents of OLETF and LETO rats were not different. No abnormalities were detected histologically in either strain. These results suggest that the occurrence of pancreatic endocrine dysfunction in OLETF rats may be due to a defect in expression of the CCK-A receptor gene, not to insulin deficiency.

Otsuka Long-Evans Tokushima Fatty (OLETF) rats revealed no or reduced expression of the cholecystokinin (CCK)-A receptor gene in the pancreas and that the pancreas of this strain of rats did not respond to CCK stimulation. We examined whether the pancreatic responses to hormonal and neural stimulation except for CCK in OLETF rats were maintained. The pancreatic responses of conscious OLETF rats to various stimuli were examined in vivo and compared with those of control (Long-Evans Tokushima; LETO) rats. Moreover, the levels of expression of CCK-A and -B receptor genes in the small intestine were examined. Pancreatic responses to intravenous injection of secretin and acetylcholine and to intracerebroventricular administration of thyrotropinreleasing hormone were comparable in OLETF and LETO rats. However, responses to intravenous injection of neuromedin C, to intraduodenal injection of capsaicin, and to intragastric injection of a liquid meal were impaired in OLETF rats. CCK-A receptor mRNA was not expressed in the small intestine of OLETF rats but was in LETO rats. The pancreatic responses to various stimuli in OLETF rats were well conserved except for the involvement of CCK-A receptor function. OLETF rats are confirmed as a new experimental model deficient in CCK-A receptor gene expression and represent a useful tool for studying the physiological role of these in vivo.

The rat possesses two pancreatic secretory trypsin inhibitors (PSTI-61 and -56). PSTI-61 has been known to stimulate cholecystokinin (CCK) release, whereas PSTI-56 did not. Both PSTIs are synthesized in the pancreatic acinar cells. CCK has a trophic effect on pancreatic acinar cells, and the exclusion of bile-pancreatic juice from the intestine has been known to be a most potent stimulator of CCK release. In the present study, we examined whether the mRNA levels of PSTI-61 and -56 produced by bile-pancreatic juice diversion were different from each other and compared the changes in CCK mRNA levels in the small intestinal mucosa and the plasma and intestinal CCK concentrations. Male Wistar rats were prepared with internal fistula and bile-pancreatic juice was excluded from the proximal intestine, being introduced into the distal ileum. Rats were sacrificed 1, 3, and 7 days after the operation. The concentrations of plasma and intestinal CCK and the levels of mRNA of CCK in the intestinal mucosa and PSTIs in the pancreas were significantly increased by bile-pancreatic juice diversion. The increase in the mRNA level of PSTI-61 was significantly higher than that of PSTI-56. Administration of CCK antagonist inhibited these changes but administration of CCK agonist could not fully reproduce these changes. These studies suggest that bile-pancreatic juice regulates gene expression of CCK and PSTIs and that the regulatory mechanisms of gene expression of PSTI-61 and -56 may be different.

The effect of a long-acting, potent synthetic analogue of prostaglandin E2, enprostil, on pancreatic exocrine secretion was examined in conscious rats. Rats were prepared with cannulae draining bile and pancreatic juice separately. Pancreatic exocrine secretion was increased by intragastric administration of enprostil but inhibited by its intravenous administration. The pancreatic response to intragastric administration of enprostil was not inhibited by the administration of cholecystokinin antagonist or secretin antibody, or by bilateral vagotomy, but was completely abolished by atropine. Therefore, intragastric administration of enprostil seemed to stimulate pancreatic exocrine secretion via a peripheral gastro-(entero)-pancreatic reflex.

Summary: 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.

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.

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.

Basal pancreatic exocrine functions as well as responses to endogenous (BPJ diversion) and exogenous (injection of CCK-8 or secretin) stimulations were examined in young (6- and 12-month-old) and old (24- to 26-month old) female Fischer 344 rats. Basal secretions were not significantly different between young and old rats. BPJ diversion significantly stimulated pancreatic secretions of fluid, bicarbonate, and protein in all animals. The pancreatic protein response (mg/kg/hr) to BPJ diversion was significantly attenuated with respect to age [57.59±16.16, 43.73±6.94, and 20.75±3.95, for 6-, 12-, 24- to 26- month-old rats, respectively, mean ±se, F(2,20)=3.49, P < 0.05]. The pancreatic responses to secretin (0.086, 0.432, and 1.728 nmol/kg) were not significantly different between young and old rats. Intravenous injection of CCK-8 (0.033, 0.167, and 0.667 nmol/kg) produced a significant increase in protein output in all age groups. In young animals, stepwise increases in protein output were observed, whereas, in old rats, increments in response to the larger two doses of CCK-8 (0.167 and 0.667 nmol) were smaller than that produced by 0.033 nmol/kg of CCK-8. In conclusion, the basal secretions in old rats were comparable with those in young ones, but the reserve capacity for protein secretion appears to decrease in old compared to young rats.

A bioassay using dispersed pancreatic acini was used to measure fasting plasma cholecystokinin (CCK) concentrations in 105 patients with various kinds of gastrointestinal diseases, 17 patients with diabetes mellitus, and 6 healthy voluntters. High plasma CCK bioactivities were observed in patients with obstructive jaundice, choledocolithiasis, and primary biliary cirrhosis. Twenty-three samples with high CCK bioactivities were assayed by the same bioassay after the addition of a specific CCK antagonist and by a CCK radioimmunoassay in order to determine whether the high CCK-like bioactivity was due to circulating CCK or other factors. High CCK bioactivities were partially inhibited by the specific CCK antagonist, CR-1409, but the activities were not totally abolished. The residual bioactivities (not inhibited by CR-1409) correlated with plasma bile acid concentrations. The inhibitable CCK bioactivities correlated with plasma CCK levels obtained by radioimmunoassay. Although the bioassay using dispersed pancreatic acini has several advantages for measuring plasma CCK, this method overestimates CCK bioactivities in patients with high plasma bile acid concentrations.

The changes in plasma and duodenal cholecystokinin (CCK) concentrations after pancreatic duct occlusion were examined in rats. The rats were sacrificed 1, 3, 7, 10, 14, and 30 days after occlusion of the duct. Histological examination showed acute inflammation on days 1 and 3 after duct occlusion, interstitial fibrosis and regenerative changes on days 7, 10, and 14, and pancreatic atrophy on day 30. The plasma CCK concentration increased from 0.45 pM to 2.0 pM after the occlusion and then remained high throughout the observation period. In contrast to the stable increase in plasma CCK concentration, the CCK content in the duodenum increased on days 1 and 3, decreased on day 7, increased on day 10, reaching over the control level on day 14, and then returned to the control level on day 30. Administration of boiled and 10-fold concentrated rat pancreatic juice or human pancreatic secretory trypsin inhibitor for seven days after pancreatic duct occlusion reversed the decrease in duodenal CCK content. The major molecular forms of duodenal CCK were CCK-8, -33, and -58. These results indicate that (1) basal plasma CCK concentration did not reflect the duodenal CCK content, (2) duodenal CCK content was well correlated with a decrease in inflammation in the pancreas, and (3) a nonenzymatic component in the pancreatic juice reversed the decrease in duodenal CCK content and body weight caused by pancreatic duct occlusion.

The role of luminal bile salts (taurocholate) in regulation of rat pancreatic secretion was examined by studies on the effects of luminal stimulants on the pancreas during infusion of various concentrations of taurocholate into the duodenum of conscious rats. Rats with external bile and pancreatic fistulae were used. For 24 h before the experiment, pancreatic juice was excluded from the intestine but bile was continuously returned to the duodenum. From the beginning of the experiment, 8–200 mM of taurocholate was infused at a rate of 1 ml/h instead of retuming the bile. Pancreatic juice was collected for a 2–h period and then 2 μ of pancreatic secretory trypsin inhibitor-61 (PSTI-61) ( monitor peptide) or partially purified putative CCK-releasing pep-tide from rat intestine (intestinal CCK-RP) was injected into the duodenum (1 ml/min). Continuous infusion of taurocholate maintained a constant rate of pancreatic secretion, except at a concentration of 8 m M, which resulted in a slight increase in pancreatic secretion. Both PSTI-61 and intestinal CCK-RP significantly increased pancreatic secretions during infusion of 20 or 40 mM taurocholate, but had no significant effect during infusion of 80 or 200 m Mtaurocholate. Therefore, higher concentrations of taurocholate in the intestine prevented the stimulatory effects of luminal stimulants, probably by preventing the latter from reaching CCK cells.