Pancreatic regenerating protein (reg I) and reg I receptor mRNA are upregulated in rat pancreas after induction of acute pancreatitis

AIM: Pancreatic regenerating protein (reg Ⅰ) stimulates pancreatic regeneration after pancreatectomy and is mitogenic to ductal and β-cells. This suggests that reg Ⅰ and its receptor may play a role in recovery after pancreatic injury. We hypothesized that reg Ⅰ and its receptor are induced in acute pancreatitis.METHODS: Acute pancreatitis was induced in male Wistar rats by retrograde injection of 3% sodium taurocholate into the pancreatic duct. Pancreata and serum were collected 12, 24, and 36 hours after injection and from normal controls (4 rats/group). Reg Ⅰ receptor mRNA, serum reg Ⅰ protein, and tissue reg Ⅰ protein levels were determined by Northern analysis, enzymelinked immunosorbent assay (ELISA), and Western analysis, respectively. Immunohistochemistry was used to localize changes in reg Ⅰ and its receptor.RESULTS: Serum amylase levels and histology confirmed necrotizing pancreatitis in taurocholate treated rats. There was no statistically significant change in serum reg Ⅰ concentrations from controls. However,Western blot demonstrated increased tissue levels of reg Ⅰ at 24 and 36 h. This increase was localized primarily to the acinar cells and the ductal cells by immunohistochemistry. Northern blot demonstrated a significant increase in reg Ⅰ receptor mRNA expression with pancreatitis. Immunohistochemistry localized this increase to the ductal cells, islets, and acinar cells.CONCLUSION: Acute pancreatitis results in increased tissue reg Ⅰ protein levels localized to the acinar and ductal cells, and a parallel threefold induction of reg Ⅰ receptor in the ductal cells, islets, and acinar cells. These changes suggest that induction of reg Ⅰ and its receptor may be important for recovery from acute pancreatitis.     

Pancreatic regenerating protein (reg Ⅰ) and reg Ⅰ receptor mRNA are upregulated in rat pancreas after induction of acute pancreatitis

AIM: Pancreatic regenerating protein (reg Ⅰ) stimulates pancreatic regeneration after pancreatectomy and is mitogenic to ductal and β-cells. This suggests that reg Ⅰ and its receptor may play a role in recovery after pancreatic injury. We hypothesized that reg Ⅰ and its receptor are induced in acute pancreatitis.METHODS: Acute pancreatitis was induced in male Wistar rats by retrograde injection of 3% sodium taurocholate into the pancreatic duct. Pancreata and serum were collected 12, 24, and 36 hours after injection and from normal controls (4 rats/group). Reg Ⅰ receptor mRNA, serum reg Ⅰ protein, and tissue reg Ⅰ protein levels were determined by Northern analysis, enzymelinked immunosorbent assay (ELISA), and Western analysis, respectively. Immunohistochemistry was used to localize changes in reg Ⅰ and its receptor.RESULTS: Serum amylase levels and histology confirmed necrotizing pancreatitis in taurocholate treated rats. There was no statistically significant change in serum reg Ⅰ concentrations from controls. However,Western blot demonstrated increased tissue levels of reg Ⅰ at 24 and 36 h. This increase was localized primarily to the acinar cells and the ductal cells by immunohistochemistry. Northern blot demonstrated a significant increase in reg Ⅰ receptor mRNA expression with pancreatitis. Immunohistochemistry localized this increase to the ductal cells, islets, and acinar cells.CONCLUSION: Acute pancreatitis results in increased tissue reg Ⅰ protein levels localized to the acinar and ductal cells, and a parallel threefold induction of reg Ⅰ receptor in the ductal cells, islets, and acinar cells. These changes suggest that induction of reg Ⅰ and its receptor may be important for recovery from acute pancreatitis.     

Therapeutic effect of basic fibroblast growth factor on experimental pancreatitis in rat

Basic fibroblast growth factor (bFGF) is one of the mitogens that facilitate endothelial proliferation and angiogenesis. This study was designed to examine the therapeutic effect of bFGF on experimental pancreatitis in rat. Edematous pancreatitis was induced by intraperitoneal injections of cerulein (50 microg/kg) at hourly intervals. BFGF (70 nmol/kg) was administered intraperitoneally after induction of pancreatitis. DNA synthesis of isolated pancreatic acinar cells of normal rats was determined as the uptake of 5-bromo-2'-deoxyuridine (BrdU) into the cells. Immunohistochemical staining of DNA synthesis in acinar cells during cerulein-induced pancreatitis was also examined with BrdU labeling in vivo technique. Cerulein administration increased serum amylase, lipase level, and wet weight of pancreatic tissue. Treatment with bFGF markedly ameliorated all these parameters. In primary culture system of isolated pancreatic acinar cells of normal rats, bFGF caused a dose-dependent increase in BrdU incorporation into DNA, showing an EC50 value of 0.8 nmol/L and a maximum response of 2.5-fold increase at a concentration of 400 nmol/L. bFGF treatment (70 nmol/kg) markedly increased BrdU labeling in the nucleus of acinar cells of the pancreatitis rats group in immunohistochemical examination when compared with control without bFGF treatment. Treatment with bFGF may represent a promising therapeutic concept for patients with acute pancreatitis.     

Effect of IS-741 on ethionine-induced acute pancreatitis in rats: relation to pancreatic acinar cell regeneration

Background: Tissue destruction arising from neutrophil infiltration of the pancreas and other organs in acute pancreatitis is supposed to be suppressed by IS-741. We studied the effect of IS-741 on acute pancreatitis induced by DL-ethionine in rats. Methods: Rats fed with a low protein diet for 11 days received daily intraperitoneal administration of DL-ethionine (20 mg/100 g) for the last 4 days of the diet. To evaluate the therapeutic effect on ethionine-induced pancreatitis, IS-741 (10 mg/kg s.c.) was administered every 8 h beginning after the second ethionine injection (IS group). An equal volume of saline was used for control rats as alternative to IS-741 (control group). The rats were killed 1, 3, 5, and 7 days after the last injection of ethionine. Blood was collected to measure concentrations of the inflammatory cytokine, interleukin-8. Histologic and biochemical examinations of the pancreas were performed. The pancreatic weight, DNA content, and protein levels were determined. The pancreas was histologically examined. Results: Pancreatic tissue in the control group showed marked infiltration of inflammatory cells, and acinar cell necrosis was widespread 1 day after the last injection of ethionine (day 1). The severity of acute pancreatitis was alleviated in rats treated with IS-741 (IS group). Pancreatic wet weight and DNA content in the IS group were higher than those in the control group on day 1. Pancreatic protein level per DNA in the IS group was higher than that in the control group on day 7. The plasma interleukin-8 level in the control group was higher than that in the IS group on day 5. Conclusions: Therapeutic administration of IS-741 ameliorated ethionine-induced acute pancreatitis in rats, and IS-741 could be a useful drug to treat patients with severe acute pancreatitis. Received: January 8, 2002 / Accepted: September 6, 2002 Reprint requests to: J. Niikawa Editorial on page 305     

Protective effect of human pancreatic secretory trypsin inhibitor on cerulein-induced acute pancreatitis in rats.

We examined the protective effect of human pancreatic secretory trypsin inhibitor (PSTI), a specific trypsin inhibitor secreted from pancreatic acinar cells into the pancreatic duct, on cerulein-induced acute pancreatitis in conscious rats. The protective effect of human PSTI-RS, an analogue of PSTI with Arg-44 to Ser substitution which has a longer half-life in vitro, was also examined. Intraperitoneal administration of a pharmacological dose of cerulein to conscious rats induced acute pancreatitis, characterized by light microscopy as cellular disorganization of the acini and interstitial edema. Intravenous infusion of human PSTI (10, 50 or 250 micrograms/rat/h) into rats with cerulein-induced acute pancreatitis decreased their pancreatic wet weight and plasma amylase concentration. It also caused a dose-dependent decrease in vacuoles in acinar cells and interstitial edema. Human PSTI-RS, which has a longer half-life in vivo, was more effective than native PSTI at the same dose rate (10 micrograms/rat/h) in reducing pancreatitis. These results suggest that human PSTI may have a beneficial effect on acute pancreatitis.     

Protease-activated receptor 2 exerts local protection and mediates some systemic complications in acute pancreatitis

BACKGROUND & AIMS: Protease-activated receptor 2 can be stimulated by interstitially released trypsin during acute inflammation of the pancreas. In this study, we investigated the roles of pancreatic and circulatory protease-activated receptor 2 in the pathogenesis of acute pancreatitis by using in vitro and in vivo model systems. METHODS: Physiological and pathologic effects of protease-activated receptor 2 activation were measured in isolated pancreatic cells and in rats with experimental pancreatitis. Consequences of protease-activated receptor 2 activation on the systemic and inflammatory responses were measured after treatments with trypsin or protease-activated receptor 2-activating peptide. RESULTS: Stimulation of protease-activated receptor 2 in rat pancreatic acinar cells activated short-lasting (Ca(2+) signaling) and long-lasting (extracellular signal-related kinase) signaling pathways and protected the cells against bile-induced cell damage. More importantly, protease-activated receptor 2 activation ameliorated the pathologic effects observed in the in vivo model of cerulein-induced pancreatitis. Trypsin in the circulation of rats with taurocholate-induced severe acute pancreatitis reached levels sufficient to activate endothelial and immune cells to stimulate nitric oxide and interleukin-8 production, respectively. Most notably, activation of systemic protease-activated receptor 2 by circulating protease-activated receptor 2 agonists induced a hemodynamic response pattern similar to that observed in rats with severe acute pancreatitis. The effects of protease-activated receptor 2 agonists and acute pancreatitis were not additive. CONCLUSIONS: These findings suggest that protease-activated receptor 2 may have a dual role in acute pancreatitis: protecting acinar and duct cells against pancreatitis-induced cell damage while mediating or aggravating the systemic complications of acute pancreatitis, which are the major cause of mortality in the early phase of necrotizing pancreatitis.     

Effect of early administration of exogenous basic fibroblast growth factor on acute edematous pancreatitis in rats

AIM: To observe the therapeutic effect of early administration of exogenous Basic fibroblast growth factor (bFGF) on acute edematous pancreatitis (AEP) in rats. METHODS: Thirty male Sprague-Dawley rats were randomly divided into three (n = 10): normal control group (groupⅠ), AEP group (groupⅡ) and AEP with bFGF treatment group (groupⅢ). AEP was induced by subcutaneous injection of cerulein (5.5μg/kg and 7.5μg/kg) at 1 h interval into rats of groupsⅡandⅢ. Three hours after induction of AEP, 100μg/kg bFGF was administrated intraperitoneally for 1h to groupⅢrats. For test of DNA synthesis in acinar cells, 5-bromo-2'-deoxyuridine (BrdU) labeling solution was intraperitoneally injected into the rats of groupsⅡandⅢ24 h after bFGF treatment. The changes in serum amylase, lipase, pancreatic tissue wet/dry ratio were detected. RESULTS: In bFGF treatment group, there was a significant decrease in the volume of serum amylase, lipase and the pancreatic wet/dry weight ratio(1383.0±94.6 U/L, 194.0±43.6 U/L, 4.32±0.32) compared to AEP group (3464±223.7 U/L, 456±68.7 U/L, 6.89±0.47) (P < 0.01), and no significant difference was found between bFGF treatment and control group (1289±94.0 U/L, 171±23.4 U/L, 4.12±0.26, P > 0.05). The inflammatory changes such as interstitial edema, polymorphonuclear neutrophils (PMNs) and vacuolization were significantly ameliorated compared to AEP group (P < 0.01). A small number of BrdU-labeled nuclei were observed in acinar cells of AEP rats (1.8±0.3 nuclei/microscopic field, n = 10) while diffuse BrdU-labeled nuclei were found in bFGF-treated rats (18.9±1.4 nuclei/microscopic field, n = 10) {P < 0.01). Immunohistochemical study showed increased DNA synthesis in pancreatic acinar cells. CONCLUSION: Early administration of exogenous bFGF has significant therapeutic effect on cerulein-induced acute edematous pancreatitis in rats. Its mechanism is related to the amelioration of inflammation and facilitation of pancreatic regeneration.     

A hierarchic approach for experimental investigations into the pathogenesis of acute pancreatitis

The complexity of pathogenesis and clinical observations of acute pancreatitis demands a simultaneous experimental investigation at various structural and functional levels. The induction of acute pancreatitis by transformation of a pancreatic edema after short-term pancreatic ischemia was used for studies on the contribution of an alteration of energy metabolism to pathogenesis. The experiments demonstrate that in 70 percent of the rats the pancreatic edema was transformed into acute pancreatitis by 20 min ischemia. This was checked by morphological and enzymic means. For studying the influence of short-term ischemia in the cellular metabolism of acinar cells, pancreatic exocrine cells have been isolated from normal pancreas or that altered by ischemia. These cells were morphologically characterized and their capacity of energy metabolism was quantified.     

Insulin is necessary for the hypertrophic effect of cholecystokinin-octapeptide following acute necrotizing experimental pancreatitis

AIM:In previous experiments we have demonstrated thatby administering low doses of cholecystokinin-octapeptide(CCK-8),the process of regeneration following L-arginine(Arg)-induced pancreatitis is accelerated.In rats that werealso diabetic(induced by streptozotocin,STZ),pancreaticregeneration was not observed.The aim of this study wasto deduce whether the administration of exogenous insulincould in fact restore the hypertrophic effect of CCK-8 indiabetic-pancreatitic rats.METHODS:Male Wistar rats were used for the experiments.Diabetes mellitus was induced by administering 60mg/kgbody mass of STZ intraperitoneally(i.p.),then,on d 8,pancreatitis was induced by 200mg/100 g body mass Argi.p.twice at an interval of 1 h.The animals were injectedsubcutaneously twice daily(at 7 a.m.and 7 p.m.)with1 μg/kg of CCK-8 and/or 2 IU mixed insulin(300g/L short-action and 700g/L intermediate-action insulin) for 14 dafter pancreatitis induction.Following this the animals werekilled and the serum amylase,glucose and insulin levelsas well as the plasma glucagon levels,the pancreaticmass/body mass ratio(pm/bm),the pancreatic contentsof DNA,protein,amylase,lipase and trypsinogen weremeasured.Pancreatic tissue samples were examined bylight microscopy on paraffin-embedded sections.RESULTS:In the diabetic-pancreatitic rats treatment withinsulin and CCK-8 significantly elevated pw/bm and thepancreatic contents of protein,amylase and lipase vs therats receiving only CCK-8 treatment.CCK-8 administeredin combination with insulin also elevated the number ofacinar cells with mitotic activities,whereas CCK-8 alonehad no effect on laboratory parameters or the mitoticactivities in diabetic-pancreatitic rats.CONCLUSION:Despite the hypertrophic effect of CCK-8being absent following acute pancreatitis in diabetic-rats,the simultaneous administration of exogenous insulin restored this effect.Our results clearly demonstrate thatinsulin is necessary for the hypertrophic effect of low-dosesof CCK-8 following acute pancreatitis.     

Insulin is necessary for the hypertrophic effect of cholecystokinin-octapeptide following acute necrotizing experimental pancreatitis

AIM: In previous experiments we have demonstrated that by administering low doses of cholecystokinin-octapeptide (CCK-8), the process of regeneration following L-arginine (Arg)-induced pancreatitis is accelerated. In rats that were also diabetic (induced by streptozotocin, STZ), pancreatic regeneration was not observed. The aim of this study was to deduce whether the administration of exogenous insulin could in fact restore the hypertrophic effect of CCK-8 in diabetic-pancreatitic rats.METHODS: Male Wistar rats were used for the experiments.Diabetes mellitus was induced by administering 60 mg/kg body mass of STZ intraperitoneally (i.p.), then, on d 8, pancreatitis was induced by 200 mg/100 g body mass Argi.p. twice at an interval of 1 h. The animals were injected subcutaneously twice daily (at 7 a.m. and 7 p.m.) with 1 μglkg of CCK-8 and/or 2 IU mixed insulin (300 g/L shortaction and 700 g/L intermediate-action insulin) for 14 d after pancreatitis induction. Following this the animals were killed and the serum amylase, glucose and insulin levels as well as the plasma glucagon levels, the pancreatic mass/body mass ratio (pm/bm), the pancreatic contents of DNA, protein, amylase, lipase and trypsinogen were measured. Pancreatic tissue samples were examined by light microscopy on paraffin-embedded sections.RESULTS: In the diabetic-pancreatitic rats treatment with insulin and CCK-8 significantly elevated pw/bm and the pancreatic contents of protein, amylase and lipase vs the rats receiving only CCK-8 treatment. CCK-8 administered in combination with insulin also elevated the number of acinar cells with mitotic activities, whereas CCK-8 alone had no effect on laboratory parameters or the mitotic activities in diabetic-pancreatitic rats.CONCLUSION: Despite the hypertrophic effect of CCK-8 being absent following acute pancreatitis in diabetic-rats,the simultaneous administration of exogenous insulin restored this effect. Our results clearly demonstrate that insulin is necessary for the hypertrophic effect of low-doses of CCK-8 following acute pancreatitis.     

Activation of adenosine A2a receptor pathway reduces leukocyte infiltration but enhances edema formation in rat caerulein pancreatitis.

INTRODUCTION: Adenosine plays important roles in a variety of pathophysiologic conditions through receptor-mediated mechanisms. Recent studies have shown that adenosine exerts potent anti-inflammatory properties that are chiefly brought about through the occupancy of the A2a receptor. AIM: To examine the effect of A2a receptor stimulation or inhibition on the pathologic findings during acute pancreatitis. METHODOLOGY: Rats were randomized into three groups and received a selective A2a receptor agonist CGS-21680 (CGS), a selective A2a antagonist 3,7-dimethyl-1-[2-propynyl]-xanthine (DMPX), or saline. Thirty minutes after the injection, acute pancreatitis was produced in the rats by seven intraperitoneal injections of caerulein. The severity of acute pancreatitis was evaluated by serum amylase activity, pancreas myeloperoxidase (MPO) activity, Evans blue extravasation, and pathologic changes of the pancreas. In addition, we investigated the effects of CGS on the pathologic findings of caerulein pancreatitis induced in neutrophil-depleted rats. RESULTS: Administration of caerulein produced hyperamylasemia and morphologic changes of the pancreas including interstitial edema, acinar cell vacuolization, and infiltration of inflammatory cells. In CGS-treated rats, the pancreatic edema and the Evans blue extravasation were aggravated significantly compared with those of saline-treated rats, whereas leukocyte infiltration and MPO activity of the pancreas were decreased. In contrast to CGS, administration of DMPX ameliorated the pancreatic edema and Evans blue extravasation. Treatment with CGS accelerated the pancreatic edema in pancreatitis even after the depletion of neutrophils. CONCLUSION: The activation of adenosine A2a receptors modulates the pathology of acute pancreatitis through at least two diverse properties. One is an anti-inflammatory effect involving neutrophils, and the other is a propagating effect for pancreatic edema formation. The actions of the A2a receptor pathways are unique, and they may have an important role in the progression of acute pancreatitis.     

Course and regression of acute interstitial pancreatitis induced in rats by repeated serial subcutaneous cholecystokinin-octapeptide injections

The aim of this study was to examine histologic and biochemical alterations in experimental acute interstitial pancreatitis (AIP) induced by serial repeated supramaximal cholecystokinin-octapeptide (CCK-OP) stimulation in rats. High doses of CCK-OP (60 micrograms/kg body wt) were administered subcutaneously (sc) six times at hourly intervals for 1 d (Group I) or for 3, 5, or 7 d (Group II). Rats were killed after 1, 3, 5, 7, and 10 d in both groups and also after 13, 20, and 27 d in Group II. During the course of the AIP, the morphological alterations were more pronounced in the repeatedly treated rats, but their appearance and disappearance essentially occurred in parallel in the two groups. Increased mitotic activity of the centroacinar and acinar cells were observed in d 5 and rose further even in Group II. The pancreatic weight and the protein and DNA contents reached a minimum on d 5 in both groups. The lowest enzyme activities did not occur in parallel. Thereafter, functional regeneration occurred despite continuing CCK-OP overstimulation in Group II. The toxicity of repeated CCK-OP hyperstimulation, thus, was limited: after its fifth administration, it failed to further aggravate the acute pancreatic damage or prevent the regeneration. This might be explained by a decreased CCK-OP sensitivity of the preexisting acinar cells, and/or increased CCK-OP tolerance of newly-formed ones.     

Study on the trophic effect of camostate mesilate on ethionine-induced pancreatic injury rat

Pancreatic injury was induced to rats with intraperitoneal injection of ethionine 60 mg per 100 g BW twice or three times weekly for 6 weeks. These rats were given 100 mg/kg of Camostate mesilate (CM) via a gastric tube daily for 14 days. CM administration resulted in an increase of pancreatic wet weight, hypertrophy and hyperplasia of acinar cells, and an increase of exocrine pancreatic function. Acini prepared from CM and ethionine-treated rats exhibited increased response to caerulein, but decreased sensitivity to caerulein. The plasma CCK level in rats with CM administration 24 hours later was higher than that without CM administration. However, there were no significant changes in plasma CCK and secretin level thereafter. We concluded that CM had a trophic effect on the pancrease with ethionine-induced pancreatic injury, and CCK was considered playing the same role in injured pancreas as the normal rat pancreas. Studies using CCK receptor antagonist are needed for further clarification.     

Failure of a potent cholecystokinin antagonist to protect against diet-induced pancreatitis in mice

The effects of a potent cholecystokinin (CCK) receptor antagonist, L-364,718, on two forms of experimental acute pancreatitis in mice were evaluated. The antagonist prevented the hyperamylasemia, pancreatic edema, and acinar cell vacuolization that followed administration of a supramaximally stimulating dose of the cholecystokinin analogue cerulein. In contrast, the same dose of L-364,718 (1 mg/kg/6 h) and an even higher dose (10 mg/kg/6 h) failed to prevent the hyperamylasemia, acinar cell necrosis, and mortality that followed administration of a choline-deficient ethionine-supplemented diet. These observations are at variance with those previously reported to follow administration of the relatively weak cholecystokinin antagonist proglumide (Niederau C et al. J Clin Invest 1986;78:1056-63). The observations reported in this communication suggest that cholecystokinin does not play an important role in diet-induced pancreatitis and that CCK receptor antagonists are unlikely to be of benefit in the treatment of clinical acute pancreatitis.     

Cholecystokinin antagonist L364,718 induces alterations in acinar cells that prevent improvement of acute pancreatitis induced by obstruction

The aim of this study was to examine the effect of the most potent CCK receptor antagonist, L364,718, on two major factors involved in pancreatitis development: enzyme load and cytosolic calcium (Ca²⁺) levels in acinar cells. L364,718 (0.1 mg/kg/12 hr) was administered from 30 min before inducing acute pancreatitis (AP) by pancreatic duct obstruction (PDO) for 48 hr. The results obtained at different AP stages in PDO rats treated and not treated with the CCK antagonist were compared. Similar increases in the intracellular enzyme content were found at earlier stages of pancreatitis in all PDO rats treated or not treated with L364,718. The CCK antagonist increased cytosolic Ca²⁺ levels up to 6 hr after administration, inducing a higher cytosolic Ca²⁺ overload at the earliest stages of pancreatitis in L364,718-treated PDO rats than in those not treated. This event might justify the higher increases in ascites volume and haematocrit found in PDO rats treated with L364,718 and the exacerbation in pancreatic morphological alterations induced by PDO. The CCK receptor antagonist L364,718 produces alterations in the acinar calcium homeostasis that prevent to reduction in the severity of pancreatitis induced by obstruction.     

Sterile inflammatory response in acute pancreatitis

The initial injury in acute pancreatitis is characteristically sterile and results in acinar cells necrosis. Intracellular contents released from damaged cells into the extracellular space serve as damage-associated molecular patterns (DAMPs) that trigger inflammation. There is increasing evidence that this sterile inflammatory response mediated through DAMPs released from necrotic acinar cells is a key determinant of further pancreatic injury, remote organ injury, and disease resolution in experimental models. A number of DAMPS, including high-mobility group box protein 1, DNA, adenosine triphosphate and heat shock protein 70, have been shown to have a role in experimental pancreatitis. Many of these DAMPs are also detectable in the human pancreatitis. Genetic deletion and pharmacologic antagonism demonstrate that specific DAMP receptors, including Toll-like receptor (TLR) 4, TLR9, and P2X7, are also required for inflammation in experimental acute pancreatitis. Downstream DAMP-sensing components include nod-like receptor protein 3, caspase 1, interleukin-1β (IL-1), IL-18, and IL-1 receptor, and also are required for full experimental pancreatitis. These DAMP-mediated pathways provide novel therapeutic targets using antagonists of TLRs and other receptors.     

Amino acid transporters expression in acinar cells is changed during acute pancreatitis

Pancreatic acinar cells accumulate amino acids against a marked concentration gradient to synthesize digestive enzymes. Thus, the function of acinar cells depends on amino acid uptake mediated by active transport. Despite the importance of this process, pancreatic amino acid transporter expression and cellular localization is still unclear. We screened mouse pancreas for the expression of genes encoding amino acid transporters. We showed that the most highly expressed transporters, namely sodium dependent SNAT3 (Slc38a3) and SNAT5 (Slc38a5) and sodium independent neutral amino acids transporters LAT1 (Slc7a5) and LAT2 (Slc7a8), are expressed in the basolateral membrane of acinar cells. SNAT3 and SNAT5, LAT1 and LAT2 are expressed in acinar cells. Additional evidence that these transporters are expressed in mature acinar cells was gained using acinar cell culture and acute pancreatitis models. In the acute phase of pancreatic injury, when acinar cell loss occurs, and in an acinar cell culture model, which mimics changes occurring during pancreatitis, SNAT3 and SNAT5 are strongly down-regulated. LAT1 and LAT2 were down-regulated only in the in vitro model. At protein level, SNAT3 and SNAT5 expression was also reduced during pancreatitis. Expression of other amino acid transporters was also modified in both models of pancreatitis. The subset of transporters with differential expression patterns during acute pancreatitis might be involved in the injury/regeneration phases. Further expression, localization and functional studies will follow to better understand changes occurring during acute pancreatitis. These findings provide insight into pancreatic amino acid transport in healthy pancreas and during acute pancreatitis injury.     

Saline Infusion Through the Pancreatic Duct Leads to Changes in Calcium Homeostasis Similar to Those Observed in Acute Pancreatitis

This work focuses on studying the early events associated with pancreatic damage after retrograde infusion through the pancreatic duct in rats. We have analyzed changes in calcium homeostasis and secretory response in pancreatic acini from rats with taurocholate-induced acute pancreatitis. Moreover, in order to test whether pancreatic duct manipulation can trigger damage inside pancreatic acinar cells, we have studied both parameters in acini from animals infused with saline. Our study demonstrates that taurocholate causes evident damage to acinar cells, impairing both calcium homeostasis and secretory response to CCK. In saline, a significant decrease in calcium cytosolic response to CCK was observed. Calcium disturbances similar to those observed in acute pancreatitis appear before secretion blockade and inflammation processes in saline treated rats. These results could be interesting since pancreatitis is associated to clinical procedures that require duct manipulation such as endoscopic retrograde cholangiopancreatography.     

CCK-A receptor induction and P38MAPK and NF-κB activation in acute pancreatitis

Bile-pancreatic duct ligation in rats excludes bile-pancreatic juice from the gut and induces acute pancreatitis. Bile-pancreatic juice exclusion from the gut results in increased plasma cholecystokinin (CCK) levels. CCK-A receptor-mediated exocrine pancreatic hyperstimulation is implicated in disease pathogenesis. In the present study, we show for the first time a progressive rise in CCK-A receptor protein expression in ligation-induced acute pancreatitis in rats. As CCK-A receptor induction could amplify CCK-mediated acinar hyperstimulation and exacerbate acinar cell stress with activation of the p38^MAPK stress kinase pathway, we studied CCK-A receptor protein expression and p38^MAPK activation in duct ligation-induced acute pancreatitis in rats. Compared to sham-operated controls, acute pancreatitis induced by bile-pancreatic duct ligation associates with a temporal increase in pancreatic CCK-A receptor protein expression, p38^MAPK expression and activation, and NF-κB activation. These findings may have significance in the mechanism of disease pathogenesis in this experimental model.     

Involvement of endogenous cholecystokinin in pancreatic regeneration after cerulein-induced acute pancreatitis.

This study was undertaken to determine the involvement of endogenous cholecystokinin (CCK) in the regeneration of pancreatic tissue after cerulein-induced acute pancreatitis treated by the CCK receptor antagonist L364,718. Acute pancreatitis was induced in rats by s.c. injections of cerulein in gelatin (12 micrograms/kg) three times a day for 2 days with controls receiving saline in gelatin. Rats were then divided into four treatment groups: saline-dimethyl sulfoxide (DMSO) (SD), saline-L364,718 (SA), cerulein-pancreatitis-DMSO (CD), and cerulein-pancreatitis-L364,718 (CA). In the first experiment, rats were treated for 3 or 10 days with DMSO or L364,718 (0.1 mg/kg, twice a day). In the second experiment, rats were treated for 13 days with DMSO or L364,718 (1.0 mg/kg, twice a day). After the rats were killed, pancreata were weighed and evaluated for their total protein, amylase, chymotrypsin, RNA, and DNA. We found that destruction of the pancreatic tissue occurred after cerulein-induced pancreatitis and that regeneration of the tissue was in progress but incomplete after 10 days; the low dose of L364,718 did not prevent regeneration. After 13 days, regeneration was still incomplete but the 1-mg dose of L364,718 strongly inhibited spontaneous regeneration. These data suggest that endogenous CCK is an important and potent trophic factor in the regeneration process of pancreatic tissue following an episode of acute pancreatitis.