Increase In Pancreatic Weight Research Articles

2156-P: Development of the Immune System in the Normal Rat Pancreas

The role of resident immune cells in organogenesis has not been extensively studied in pancreas. We hypothesized that during the critical stage of ß-cell remodeling during the newborn period, immune cell populations would also change. Using flow cytometry and immunohistochemistry, we identified immune cell populations in the endocrine (islets) and exocrine portion of the pancreas at postnatal day 1, 7 and 14. When corrected for the expected increase in pancreatic weight, immune cell populations increase in the exocrine pancreas in males and females from P1 to P7 but not further at P14. Interestingly, in islets the number of immune cells further increases in males from P7 to P14. Macrophages, T cells, B cells, granulocytes and NK cells are present in islets and exocrine pancreas. Macrophages are the dominant population in islets (M: 47%, F: 47%) and exocrine (M:30%, F: 34%) pancreas. In islets, M2 macrophages are favored at P1. M1 macrophages dramatically decrease with age. In exocrine pancreas, M1 macrophages are initially favored, but with age the M2 population increases. T cells are also present in islets (M:6%, F:6%) and exocrine (M:8%, F: 6%) pancreas. Cd3+ Cd4- Cd8- is the dominant T cell population at P1 but decreases with age replaced by Cd3+ Cd4+ Cd8- cells. In islets from male, but not females, the number of T cells, specifically Cd4+ T cells, increases with age. B cells (Cd45Ra+) are present in islets (M:20%, F:19%) and exocrine (M:20%, F:25%) pancreas and numbers do not change with age. Neutrophils (HIS48hi Cd68) are also present in islets (M:6%, F:6%) and exocrine (M:13%, F: 10%) pancreas. NK cells are a minor cell population present at about 1% of total immune cells in male and female pancreas at P1. Interestingly, NK cells increase with age in females in islets and exocrine pancreas. These data demonstrate significant sex specific changes in the pancreas during the critical period of postnatal pancreas development suggesting a role for immune cells in normal postnatal development and function in the endocrine and exocrine pancreas. Disclosure T. Golden: None. G. Worthen: None. R.A. Simmons: None. Funding National Institutes of Health

Capsaicin-Sensitive Sensory Nerves Are Necessary for the Protective Effect of Ghrelin in Cerulein-Induced Acute Pancreatitis in Rats.

Ghrelin was shown to exhibit protective and therapeutic effect in the gut. Aim of the study was to investigate the role of sensory nerves (SN) in the protective effect of ghrelin in acute pancreatitis (AP). Studies were performed on male Wistar rats or isolated pancreatic acinar cells. After capsaicin deactivation of sensory nerves (CDSN) or treatment with saline, rats were pretreated intraperitoneally with ghrelin or saline. In those rats, AP was induced by cerulein or pancreases were used for isolation of pancreatic acinar cells. Pancreatic acinar cells were incubated in cerulein-free or cerulein containing solution. In rats with intact SN, pretreatment with ghrelin led to a reversal of the cerulein-induced increase in pancreatic weight, plasma activity of lipase and plasma concentration of tumor necrosis factor-α (TNF-α). These effects were associated with an increase in plasma interleukin-4 concentration and reduction in histological signs of pancreatic damage. CDSN tended to increase the severity of AP and abolished the protective effect of ghrelin. Exposure of pancreatic acinar cells to cerulein led to increase in cellular expression of mRNA for TNF-α and cellular synthesis of this cytokine. Pretreatment with ghrelin reduced this alteration, but this effect was only observed in acinar cells obtained from rats with intact SN. Moreover, CDSN inhibited the cerulein- and ghrelin-induced increase in gene expression and synthesis of heat shock protein 70 (HSP70) in those cells. Ghrelin exhibits the protective effect in cerulein-induced AP on the organ and pancreatic acinar cell level. Sensory nerves ablation abolishes this effect.

Protective Effect of Pretreatment with Acenocoumarol in Cerulein-Induced Acute Pancreatitis.

Coagulation is recognized as a key player in inflammatory and autoimmune diseases. The aim of the current research was to examine the effect of pretreatment with acenocoumarol on the development of acute pancreatitis (AP) evoked by cerulein. Methods: AP was induced in rats by cerulein administered intraperitoneally. Acenocoumarol (50, 100 or 150 µg/kg/dose/day) or saline were given once daily for seven days before AP induction. Results: In rats with AP, pretreatment with acenocoumarol administered at the dose of 50 or 100 µg/kg/dose/day improved pancreatic histology, reducing the degree of edema and inflammatory infiltration, and vacuolization of acinar cells. Moreover, pretreatment with acenocoumarol given at the dose of 50 or 100 µg/kg/dose/day reduced the AP-evoked increase in pancreatic weight, serum activity of amylase and lipase, and serum concentration of pro-inflammatory interleukin-1β, as well as ameliorated pancreatic DNA synthesis and pancreatic blood flow. In contrast, acenocoumarol given at the dose of 150 μg/kg/dose did not exhibit any protective effect against cerulein-induced pancreatitis. Conclusion: Low doses of acenocoumarol, given before induction of AP by cerulein, inhibit the development of that inflammation.

Glucagon-like peptide-1 receptor agonists increase pancreatic mass by induction of protein synthesis.

Glucagon-like peptide-1 (GLP-1) controls glucose homeostasis by regulating secretion of insulin and glucagon through a single GLP-1 receptor (GLP-1R). GLP-1R agonists also increase pancreatic weight in some preclinical studies through poorly understood mechanisms. Here we demonstrate that the increase in pancreatic weight following activation of GLP-1R signaling in mice reflects an increase in acinar cell mass, without changes in ductal compartments or β-cell mass. GLP-1R agonists did not increase pancreatic DNA content or the number of Ki67(+) cells in the exocrine compartment; however, pancreatic protein content was increased in mice treated with exendin-4 or liraglutide. The increased pancreatic mass and protein content was independent of cholecystokinin receptors, associated with a rapid increase in S6 phosphorylation, and mediated through the GLP-1R. Rapamycin abrogated the GLP-1R-dependent increase in pancreatic mass but had no effect on the robust induction of Reg3α and Reg3β gene expression. Mass spectrometry analysis identified GLP-1R-dependent upregulation of Reg family members, as well as proteins important for translation and export, including Fam129a, eIF4a1, Wars, and Dmbt1. Hence, pharmacological GLP-1R activation induces protein synthesis, leading to increased pancreatic mass, independent of changes in DNA content or cell proliferation in mice.

JTT-130, a novel intestine-specific inhibitor of microsomal triglyceride transfer protein, improves hyperglycemia and dyslipidemia independent of suppression of food intake in diabetic rats.

We investigated the effects of JTT-130 on glucose and lipid metabolism independent of the suppression of feeding by comparing with pair-fed animals. Male Zucker diabetic fatty (ZDF) rats were divided into control, JTT-130 treatment, and pair-fed groups. The rats were fed with a regular powdered diet with or without JTT-130 as a food admixture for 6 weeks. We compared the effects on glucose and lipid metabolism in JTT-130 treatment group with those in pair-fed group. Results. Hyperglycemia in ZDF rats was prevented in both JTT-130 treatment and pair-fed groups, but the prevention in pair-fed group became poor with time. Moreover, reduction in plasma cholesterol levels was observed only in JTT-130 treatment group. JTT-130 treatment group showed improved glucose tolerance at 5 weeks after treatment and significant elevation of portal glucagon-like peptide-1 (GLP-1) levels. The hepatic lipid content in JTT-130 treatment group was decreased as compared with pair-fed group. Furthermore, pancreatic protection effects, such as an increase in pancreatic weight and an elevation of insulin-positive area in islets, were observed after JTT-130 treatment. Conclusions. JTT-130 improves hyperglycemia and dyslipidemia via a mechanism independent of suppression of food intake, which is ascribed to an enhancement of GLP-1 secretion and a reduction of lipotoxicity.

Ellagic Acid Inhibits Pancreatic Fibrosis in Male Wistar Bonn/Kobori Rats

The key pathological features of chronic pancreatitis are chronic inflammation, acinar atrophy, and pancreatic fibrosis. We have previously shown that ellagic acid, a plant-derived polyphenol found in fruits and nuts, inhibited activation of pancreatic stellate cells, a major profibrogenic cell type in the pancreas, in vitro. Here we examined whether ellagic acid inhibited the development of pancreatic fibrosis in vivo. Ellagic acid was administered orally in the diet to ten-week-old male Wistar Bonn/Kobori rats, an experimental model of spontaneous chronic pancreatitis, for ten weeks. Ellagic acid (100 mg/kg body weight/day) attenuated pancreatic inflammation and fibrosis. The protective effects were confirmed by an increase in pancreatic weight and decreases in myeloperoxidase activity (an index of neutrophil infiltration), collagen content, transforming growth factor-beta1 expression, and the number of alpha-smooth muscle actin-positive cells (activated pancreatic stellate cells) and ED-1-positive cells (macrophages/monocytes). Ellagic acid inhibited the production of reactive oxygen species in pancreatic stellate cells in response to transforming growth factor-beta1 or platelet-derived growth factor. Our results suggest that ellagic acid might be a candidate for treatment of chronic pancreatitis.

Dietary lectins can stimulate pancreatic growth in the rat.

Lectins are proteins or glycoproteins of nonimmune origin, which bind specifically to carbohydrate structures. They are widespread in the human diet, and many are resistant to digestion. High doses of lectins have been shown to stimulate intestinal and pancreatic growth. The aim of the present study was to investigate the long-term actions of low doses of lectins on the rat intestine and pancreas. A long-term carcinogenesis study was performed using low levels (40 micro g/rat/day) of peanut (PNA) or mushroom lectin (ABA) which bind to O-linked (mucin-type) oligosaccharides in the gut. While this was primarily designed as a colon carcinogenesis study, the pancreas was also investigated. No significant changes in colon carcinogenesis were seen, however, the colons were slightly heavier in the lectin treated groups. The weight of the pancreas was significantly greater (by 18 and 23%) in both lectin treated groups (P < 0.03/0.001). The weights of the acini and septal tissue were also increased by 39-46% in PNA and ABA fed animals, respectively (P < 0.002); there was no significant change in the endocrine pancreas. In conclusion, long-term feeding of low doses of lectin can influence pancreatic growth, and this trophic action may have potential adverse implications for the development of pancreatic cancer in humans.

Effect of hypergastrinemia on pancreatic carcinogenesis

Background: Previous studies in our laboratory demonstrated that pancreatic carcinomas in rodents express receptors for the peptide hormone gastrin that are not present in normal adult pancreas. In view of an abundant literature suggesting that gastrin may promote growth of various gastrointestinal tissues and tumors, the effect of hypergastrinemia on the process of pancreatic carcinogenesis was evaluated. Methods: Rats received subcutaneous injections of the pancreatic carcinogen azaserine at 19 and 26 days of age. Starting at 12 months of age, animals were randomized to treatment with the proton pump inhibitor lansoprazole or vehicle by gavage for 6 months. At autopsy, pancreatic wet weight normalized to body weight was recorded, as well as the number of benign and malignant pancreatic lesions. Results: Serum gastrin levels were determined by radioimmunoassay and showed a greater than two-fold increase in lansoprazole-treated animals. Pancreatic wet weight in hypergastrinemic rats was increased compared to controls (p <0.05). Premalignant lesions such as acidophilic atypical acinar cell foci, adenomas, heterogeneous phenotypic populations of nodules within nodules, and carcinoma-in-situ were not increased in the hypergastrinemic group. Likewise, there was no difference in the incidence of invasive carcinoma in hypergastrinemic animals (10%) compared to controls (5.7%). Conclusion: Hypergastrinemia stimulated an increase in pancreatic weight, but did not stimulate development of premalignant lesions or progression to cancer in the azaserine model of rat pancreatic acinar cell carcinoma.

Postruminal Administration of Partially Hydrolyzed Starch and Casein Influences Pancreatic α-Amylase Expression in Calves

The objective was to examine the effects of postruminal partially hydrolyzed starch (SH) and/or casein on the expression of pancreatic alpha-amylase mRNA, protein and activity in calves. Holstein calves [(n = 24) 88 plus minus 3 kg body weight (BW)], fitted with abomasal infusion cannulas, were randomly assigned within block (week of infusion) to one of four abomasal infusion treatments. Calves were fed an alfalfa-based diet, and SH [4 g/(kg BW.d)] and/or casein [0.6 g/(kg BW.d)] was infused abomasally for 10 d before tissue collection. There was a SH x casein interaction (P < 0.10) for pancreatic weight (g and g/kg BW) because casein increased pancreatic weight in the absence of SH but did not influence pancreatic weight in the presence of SH. Pancreatic alpha-amylase mRNA tended to be lower (P = 0.06) and protein and activity (U/g pancreas and U/g protein) were lower (P = 0.02) in calves receiving abomasal SH. The concentration of pancreatic trypsin activity (U/g pancreas and U/g protein) was lower (P < 0.03) in calves receiving abomasal SH. There was a SH x casein interaction for total alpha-amylase and trypsin activity [U/pancreas and U/(pancreas.kg BW)] because casein increased total activity in the absence of SH but not in the presence of SH. These data suggest that increases in small intestinal protein flow enhance pancreatic weight and thus total pancreatic alpha-amylase and trypsin activity, yet small intestinal SH inhibits the increase in pancreatic weight resulting from increased small intestinal protein flow. Additionally, postruminal SH decreases alpha-amylase expression largely by translational events.

Effects of methimazole pretreatment on cerulein induced acute pancreatitis in rats

Many interrelationships exist between the thyroid gland and the gastrointestinal tract. Several past and recent studies have shown that the thyroid gland profoundly influences the structure and function of the exocrine pancreas in the rat. In the present study we investigated the effect of methimazole (METZ), an antithyroid drug, on cerulein induced acute pancreatitis (AP) in rats. Rats were divided into 3 groups (10-12 weeks age, 200-250 g weight, n: 10). Group B was made hypothyroid with methimazole 5 mg/kg daily for 10 days and the others were untreated euthyroid groups. After 10 days, acute pancreatitis was induced with four doses of 20 microg/kg body weight of cerulein administered s.c at hourly intervals in group A and B while the control group C was given 4 doses of I ml saline. Pancreas wet weight (mg), plasma amylase activity (IU/l) and pancreatic histology were used as endpoints to quantify the severity of the AP. Plasma tri-iodothyronine (T3) (ng/dl) and thyroxine (T4) (microg/dl) levels were significantly reduced after METZ treatment for 10 days (p < 0.01). METZ pretreatment reduced significantly the cerulein induced increase in pancreatic weight (1,205 +/- 12 mg in METZ treated AP group versus 1,617 +/- 14 mg in AP group, p < 0.05) and the rise in amylase activity (7,078 +/- 816 IU/l in METZ treated AP group versus 8,611 +/- 830 IU/l in AP group p < 0.05). METZ reduces the severity of cerulein induced AP in rats. This effect might be through its antithyroid property.

Effects of Intraluminal Trypsin and Bile on the Exocrine and Endocrine Pancreas After Pancreaticobiliary Diversion and Biliodigestive Shunt

Pancreaticobiliary diversion (PBD) and biliodigestive shunt (BDS) cause long-standing hypercholecystokininemia followed by pancreatic hyperplasia. These changes have been suggested to be due to the lack of intraluminal trypsin and bile, respectively, in the upper small intestine. The aim of these experiments was to study the effect of restoration of intraluminal trypsin and bile on plasma levels of cholecystokinin (CCK) and the changes found in exocrine and endocrine pancreas after PBD and BDS. Male Sprague-Dawley rats were used. PBD was done in 16 rats, eight of which had trypsin dissolved in 50 mM sodium bicarbonate (SB), and eight had SB only by gastric intubation twice daily. BDS was done in another 16 rats, eight of which had bile dissolved in SB, and eight had SB in a similar manner. Sham-operated rats had SB and served as controls. After 4 weeks, the rats were killed, and the concentrations of circulating CCK, gastrin, glucose, glucagon, and insulin were determined. The pancreas was removed, weighed, and analyzed for contents of water, protein, and DNA. In another study, PBD-operated rats got trypsin in varying dosages or trypsin and taurocholate in combination for 2 weeks before death. The concentrations of plasma CCK and glucagon were elevated after both PBD and BDS. PBD decreased the concentration of gastrin in plasma. PBD caused an increase of pancreatic weight and the contents of protein and DNA. Trypsin substitution to PBD-operated rats did not affect plasma CCK or glucagon levels, but the PBD-induced increases in weight and DNA content were counteracted by trypsin. Higher dosages of trypsin did not further influence the effects seen after PBD. Pancreatic weight and DNA content were increased after BDS. Bile administration completely abolished the increase in plasma CCK and glucagon, as well as the gain in pancreatic weight, and reduced the increase in pancreatic DNA. Substitution with bile to BDS-operated rats abolished the increase in the plasma levels of CCK and glucagon, as well as the trophic effects on the pancreas. Trypsin substitution to PBD-operated rats partly reversed the trophic effects on the pancreas but not the hormonal changes in plasma. Thus the trophic effects on the pancreas exerted by BDS seem to be dependent on the lack of bile in the upper small intestine, whereas the effects of PBD only partly are a consequence of the absence of intraluminal trypsin.

Continuous Infusion of Cholecystokinin Leads to Down-Regulation of the Cholecystokinin-A Receptor in the Rat Pancreas

Infusion of sulphated cholecystokinin-8 (CCK-8S) in rats transiently increased the proliferation of pancreatic acinar cells, whereas the CCK-A receptor antagonist devazepide decreased such proliferation. This effect ceased after 3 days. CCK-8S or devazepide injected twice daily induced a persistent effect on the cell proliferation involving the major cells of the exocrine pancreas. The aim of this study was to examine the effect of continuous infusion of CCK-8S and devazepide on CCK-A receptor gene expression. Male Sprague-Dawley rats received subcutaneous continuous infusion of 5 microg/kg/h CCK-8S, 200 microg/kg/h devazepide, or 1% bovine serum albumin (BSA) by means of osmotic minipumps. The rats were killed after 4 days; I h before being killed they received 5-bromo-2-deoxyuridine (BrdU) intraperitoneally. Plasma was collected for analysis of CCK. The pancreas was dissected, and indirect immunofluorescence for BrdU and CCK-A receptor was performed. In situ hybridization to CCK-A receptor mRNA was performed for examination and semiquantification of receptor gene expression. Continuous infusion of CCK-8S led to a sixfold increase in plasma CCK and a 40% increase in pancreatic weight. Devazepide did not affect the CCK level but decreased the pancreatic weight by 24% compared with BSA-infused rats. The BrdU labeling indicated that CCK-8S had no effect on cell proliferation. Immunofluorescence for the CCK-A receptor showed a decreased labeling intensity after CCK-8S infusion. The mean optical density of in situ hybridization labeling of the sections from CCK-8S-treated rats was decreased to 37% +/- 3% of that in controls. Devazepide did not affect the CCK-A receptor gene expression. Continuous stimulation of the CCK-A receptor led to a downregulation of the receptor gene expression in pancreatic acinar cells and decreased labeling of the receptor at immunohistochemistry. The results suggest that down-regulation of the receptor is a protective mechanism against overstimulation.

Epidermal Growth Factor Protects against Pancreatic Damage in Cerulein-Induced Pancreatitis

Epidermal growth factor (EGF) exhibits gastroprotective and ulcer-healing action. These observations prompted us to determine the influence of EGF on cerulein-induced pancreatitis (CIP) in the rat. Acute pancreatitis was induced by subcutaneous infusion of cerulein (10 μg/kg/h) for 5 h. Initially EGF was administrated twice at doses of 1, 5, 10 or 100 μg/kg s.c. (first injection 30 min prior to cerulein infusion, and the second injection 2.5 h after the start of cerulein infusion) and from this part of study 10 μg/kg was chosen for the next experiments. CIP led to a significant decrease in DNA synthesis and a reduction in pancreatic blood flow (PBF) by 42 and 30%, respectively, as well as a significant increase in pancreatic weight, plasma amylase concentration, plasma interleukin-1β (IL-1β) level and the development of the histological signs of pancreatic damage with marked edema, leukocyte infiltration and vacuolization of acinar cells. Treatment with EGF attenuated the pancreatic tissue damage in CIP as manifested by partial reversal of the drop in DNA synthesis and improvement of pancreatic histology. Moreover, EGF administration attenuated the fall in PBF and significantly reduced the cerulein-evoked increase in pancreatic weight. Also plasma amylase and IL-1β were decreased in rats treated with EGF. We conclude that: (1) EGF exerts a protective effect against CIP, and (2) the beneficial activity of EGF in CIP seems to depend on the increase in pancreatic cell proliferation, the reduction in cytokine generation and the attenuation of the fall in PBF.

Effects of Epidermal Growth Factor, Cholecystokinin, and Secretin on Growth of the Alimentary Tract in the Neonatal Guinea Pig

Gut hormones and growth factors are likely to be involved in the functional changes and substantial growth of the alimentary tract that occurs during early neonatal life. The present experiments investigated the effects of continuous subcutaneous infusion of cholecystokinin (CCK), secretin, and epidermal growth factor (EGF) in neonatal guinea pigs for 4 or 15 days. At doses of 20, 100 or 500 pmol/kg/h, CCK and secretin had no effect on alimentary tract organs except for an increase in pancreatic weight at 4 days with the highest dose of CCK and an increase in stomach weight at 4 days with the highest dose of secretin. In contrast, EGF showed dose-dependent and time-dependent effects on all the alimentary tract organs when infused at 70, 210 and 630 pmol/kg/h. These results suggest that EGF, but not CCK or secretin, is likely to be an important trophic factor during the neonatal period.

Evidence That A8947 Enhances Pancreas Growth via a Trypsin Inhibitor Mechanism

A8947 is a member of the sulfonyl urea class of compounds and is the active ingredient in a commercial broad leaf herbicide. This compound has been shown to produce pancreatic hypertrophy in rats, mice, and dogs. The objectives of this study were to investigate the mechanism(s) for the A8947 induction of pancreatic acinar cell hypertrophy and proliferation and to evaluate whether these pancreatic changes are reversible. A8947 was fed to male Crl:CD BR rats for up to 28 days (0, 300, 10,000, 30,000 ppm) or 56 days (0, 30,000 ppm). Rats were terminated on Test Days 7, 14, and 28 to assess the time course and dose response for the A8947-induced pancreatic changes, while rats terminated on Test Day 56 were used to assesss the reversibility of the pancreas effects at 30,000 ppm A8947. A8947 produced significant increases in pancreatic weight and acinar cell proliferation and diffuse acinar cell hypertrophy in 7 days at 10,000 and 30,000 ppm dose levels. By Day 14, absolute pancreas weights in the 10,000 and 30,000 ppm groups were maximally increased and remained at these levels throughout the study. In contrast, acinar cell proliferation in the 30,000 ppm group was still elevated at Test Day 14, but attenuated relative to the 7-day response, and returned to control levels by Test Day 28. No effects were observed at 300 ppm after a 28-day exposure period, while complete reversibility of A8947-induced pancreatic effects was demonstrated at 30,000 ppm following a 1-month recovery period (Test Day 56). Cholecystokinin (CCK) levels were increased by A8947 and closely followed the time course for pancreatic changes. MK-329, a specific CCKAreceptor antagonist, completely ablated the ability of 30,000 ppm A8947 to increase pancreas weight following 7 days of exposure. A8947 did not bind the CCKAreceptor in a receptor competition assay, negating any potential agonist mechanism. A8947 did, however, inhibit trypsinin vitro,suggesting a mechanism of action similar to that of raw soy protein, in which trypsin inhibitionin vivoresults in increased CCK levels followed by pancreatic acinar cell hypertrophy and proliferation.

Effect of a new CCK-A receptor antagonist, dexloxiglumide, on the exocrine pancreas in the rat

The effect of dexloxiglumide, a new potent cholecystokinin (CCK) antagonist, on pancreatic enzyme secretion and growth was studied in the rat. Pancreatic exocrine secretion was studied both in vitro (isolated and perfused pancreatic segments) and in vivo (anaesthetized animals with cannulation of the common bile duct) whereas the trophic effect was investigated after short-term (7 days) administration of the CCK-agonist, caerulein, or camostate (a potent trypsin inhibitor), with or without dexloxiglumide. CCK-8 stimulated amylase release from in vitro pancreatic segments in a concentration-dependent manner. Dexloxiglumide displaced the concentration response curves to CCK-8 to the right without affecting the maximum response, suggesting a competitive antagonism. The Schild plot analysis of data gave a straight line with a slope (0.90±0.36) not significantly different from unity. The calculated pA 2 for dexloxiglumide was 6.41 ± 0.38. In vivo experiments confirmed results from in vitro studies since intravenous dexloxiglumide reduced pancreatic exocrine secretion induced by submaximal CCK-8 stimulation (0.5 nmol/kg/h) in a dose-dependent manner, the ID 50 being 0.64 mg/kg. Both exogenous and endogenous (released by camostate) CCK increased the weight of the pancreas, the total pancreatic protein and DNA, trypsin and amylase content. Dexloxiglumide (25 mg/kg), administered together with caerulein (1 μg/kg), reduced the peptide-induced increase in pancreatic weight, protein and enzyme content. Similarly, when dexloxiglumide was given together with camostate (200 mg/kg), all the observed changes were reduced by concomitant administration of the antagonist. These results demonstrate the ability of dexloxiglumide to antagonize the effects of CCK on pancreatic secretion and growth, suggesting that this compound is a potent and selective antagonist of CCK-A-receptors in the pancreas.

Apoptosis Participates in the Remodeling of the Endocrine Pancreas in the Neonatal Rat

In rodents, shortly after birth a lack of increase in pancreatic weight and in islet mass have been reported during a time of overall body weight increase. To understand this regulation of the neonatal growth of the β cell mass, we studied Sprague Dawley rats at 2, 9, 13, 17, 20, 24, and 31 days of age for β cell replication, β cell mass, and cell size and for the presence of β cell apoptosis. β cell mass was stable from 2–20 days (range: 0.91 ± 0.2 to 1.33 ± 0.23 mg) and increased thereafter. β cell replication progressively decreased. Condensed apoptotic nuclei were identified and counted on paraffin sections using the fluorescent dye propidium iodide. Apoptoticβ cell nuclei were found at a basal rate (1.54 ± 0.22%) at 2, 9, and again after 20 days of age. However, at 13 and 17 days, the incidence of apoptosis was significantly increased (3.64 ± 0.45%). The decreased replication and the increased incidence of apoptosis in the β cells strongly suggest a wave of neogenesis of β cells to maintain the constant β cell mass. These data show that the endocrine pancreas undergoes significant modification during neonatal life and that apoptosis is an important mechanism in this remodeling of the β cell mass. Whether a selective deletion of some population ofβ cells occurs is unclear, but a dysregulation of this remodeling process could have important effects on the pancreatic β cell mass.

Apoptosis participates in the remodeling of the endocrine pancreas in the neonatal rat.

In rodents, shortly after birth a lack of increase in pancreatic weight and in islet mass have been reported during a time of overall body weight increase. To understand this regulation of the neonatal growth of the beta cell mass, we studied Sprague Dawley rats at 2, 9, 13, 17, 20, 24, and 31 days of age for beta cell replication, beta cell mass, and cell size and for the presence of cell apoptosis. beta cell mass was stable from 2-20 days (range: 0.91 +/- 0.2 to 1.33 +/- 0.23 mg) and increased thereafter. beta cell replication progressively decreased. Condensed apoptotic nuclei were identified and counted on paraffin sections using the fluorescent dye propidium iodide. Apoptotic beta cell nuclei were found at a basal rate (1.54 +/- 0.22%) at 2, 9, and again after 20 days of age. However, at 13 and 17 days, the incidence of apoptosis was significantly increased (3.64 +/- 0.45%). The decreased replication and the increased incidence of apoptosis in the beta cells strongly suggest a wave of neogenesis of beta cells to maintain the constant beta cell mass. These data show that the endocrine pancreas undergoes significant modification during neonatal life and that apoptosis is an important mechanism in this remodeling of the beta cell mass. Whether a selective deletion of some population of beta cells occurs is unclear, but a dysregulation of this remodeling process could have important effects on the pancreatic beta cell mass.

The influence of acute ethanol ingestion on phospholipase D activity in rat pancreas. An in vitro and in vivo study.

Since phosphatidic acid (PA), a product of phospholipase D(PLD), is known as a second messenger probably involved in cell proliferation and differentiation, our results potentially suggest a new mechanism for pancreatic tissue injury after ethanol ingestion. The mechanisms by which ethanol causes pancreatic injury are still not clear. In vitro studies have suggested a relationship of PLD to ethanol metabolism. This study was undertaken to establish the involvement of PLD in ethanol metabolism in isolated pancreatic acini and to determine the influence of acute ethanol ingestion on PLD activity in pancreas and pancreatic growth after cerulein (Ce) infusion. Dispersed pancreatic acini prelabeled with 3H myristic acid were incubated with 500 pM Ce in the presence of different concentrations of ethanol; then labeled PA and phosphatidylethanol (PEt) production were measured under the same experimental conditions. For in vivo study, male rats were infused with Ce (0.25 microgram/kg/h) or saline; 1 h before infusion, animals were treated with 40% ethanol (5 g/kg p.o.) or saline, respectively. After 1, 2, and 48 h of Ce infusion, rats were killed; dispersed pancreatic acini were then prepared and PLD activity was measured. Pancreatic weight, protein, RNA, and DNA content were also established. The production of PEt in vitro after Ce stimulation was significantly elevated with 1% ethanol in the medium. In the presence of different concentrations of ethanol (0.5-2%), a significant inhibition of PA accumulation in in vitro experiments was observed. The decrease of PA accumulation with ethanol was parallel to the increase of PEt production under the same experimental conditions. PLD activity was significantly elevated after 1 and 2 h of Ce infusion (116 and 105%, respectively), reaching control value after 48 h. Acute ethanol ingestion significantly diminished PLD activity after 1 and 2 h. After 48 h of Ce infusion, a significant increase in pancreatic weight, protein, RNA, and DNA content in pancreatic tissue was found. Ethanol was not able to influence pancreatic weight, proteins and RNA content. However, it had the potency to diminish DNA content after 48 h of Ce infusion.

Influence of capsaicin-sensitive afferent neurons and nitric oxide (NO) on cerulein-induced pancreatitis in rats.

Stimulation of afferent neurons by capsaicin exerts protective activity against cerulein-induced pancreatitis. This action is dependent on endogenous release of nitric oxide (NO). Deactivation of afferent neurons by high doses of capsaicin contributes to the severity of pancreatitis. This action involves mainly decreased pancreatic blood flow (PBF). Afferent nerves and NO cooperate in the maintenance of the integrity of pancreatic tissue. Stimulation of capsaicin-sensitive afferent fibers protects gastric mucosa against damage and causes changes in mucosal blood flow. The aim of the present study was to determine the role of stimulation or ablation of capsaicin-sensitive neurons and NO in the course of cerulein-induced pancreatitis in the rat. Low and high doses of capsaicin were administered to animals with pancreatitis and to those without pancreatitis. The effect of several parameters was assessed. NO activity was blocked by NG-nitro-L-arginine. We found that a low dose of capsaicin administered intragastrically caused an increase in PBF. A neurotoxic dose of capsaicin caused a decrease in PBF, RNA content, and DNA synthesis. Pancreatitis led to a significant decrease in PBF and DNA synthesis, but an increase in pancreatic weight, protein content, plasma amylase concentration, and neutrophil adherence. Stimulatory doses of capsaicin attenuated the pancreatic tissue damage of pancreatitis, and alteration of PBF, DNA synthesis, and neutrophil adherence. Capsaicin-induced ablation of afferent neurons caused an increase in all indicators of pancreatic damage. Blocking NO enhanced pancreatic damage, and this was reversed by addition of L-arginine.