Cerulein-induced Acute Pancreatitis In Rats Research Articles

Heat Shock Proteins and Autophagy in Rats with Cerulein-Induced Acute Pancreatitis

Background/AimsHeat shock proteins (HSPs) protect rats from cerulein-induced acute pancreatitis (AP) by preventing the subcellular redistribution of cathepsin B and the activation of trypsinogen. Autophagy plays a critical role in the secretion of digestive enzymes and triggering of cerulein-induced AP via the colocalization of trypsinogen and lysosomes. Therefore, using a rat cerulein-induced AP model, we investigated whether HSPs prevent AP by regulating autophagy.MethodsTwelve hours after fed standard laboratory chow and water, the experimental groups (cerulein, water-immersion [WI]-cerulein and heat-shock [HS]-cerulein) and the control groups (control, WI, and HS) received one intraperitoneal injection of cerulein (50 µg/kg) or saline, respectively. All of the rats were sacrificed at 6 hours after injection. The severity of the AP was assessed based on the serum amylase level and the histological and electron microscopy findings. Western blotting was also performed for HSP60/70 and LC3B-II.ResultsWI and HS induced HSP60 and HSP70, respectively. The induced HSP60/70 effectively prevented the development of cerulein-induced AP. Autophagy developed in the rats with cerulein-induced AP and was documented by the expression of LC3-II and electron microscopy findings. The WI-stressed rats and HS-treated rats did not develop cerulein-induced autophagy.ConclusionsHSPs exert protective effects against cerulein-induced AP in rats by inhibiting autophagy.

セルレイン誘発急性膵炎モデルにおけるアンチトロンビンIII投与での病態改善効果の検討

セルレイン誘発急性膵炎モデルにおけるアンチトロンビンIII投与での病態改善効果の検討

Antithrombin III Prevents Cerulein-Induced Acute Pancreatitis in Rats

Systemic inflammatory mediators, including the protein high-mobility group box 1 (HMGB1), play an important role in the development of acute pancreatitis. Anticoagulants, such as antithrombin III (AT III), inhibit inflammation resulting from various causes, but their mechanism of action is not well understood. Because acute pancreatitis is a severe inflammatory disease, we hypothesized that AT III would inhibit inflammation and prevent cerulein-induced acute pancreatitis. Experimental animals received or were saline injected with a bolus of 250 IU/kg of AT III followed by intraperitoneal injections of 50 mg/kg of cerulein. Levels of cytokines (interleukin 6 and tumor necrosis factor alpha), nitric oxide (NO), and HMGB1 were measured in serum and pancreatic tissue at regular intervals for 12 hours after the cerulein injection. Pancreas histopathology and wet-dry ratio significantly improved in the AT III-injected (250 IU/kg) animals compared with the saline-injected rats. Serum and pancreas HMGB1 levels decreased over time in AT III-treated animals. Antithrombin III also decreased cytokine, NO, and HMGB1 levels during cerulein-induced inflammation. As a result, AT III ameliorated the pathologic pancreas in the rat model of cerulein-induced acute pancreatitis. Antithrombin III treatment inhibited the secretion of cytokines, NO, and HMGB1 and prevented cerulein-induced acute pancreatitis in the rat model.

The effects of a new human leukocyte elastase inhibitor (recombinant guamerin) on cerulein-induced pancreatitis in rats

Background Pancreatic and neutrophil elastase can aggravate or induce acute pancreatitis. Although increased elastase levels in the plasma of pancreatitis patients and animal models have been reported, the mechanism by which elastase is involved in the pathogenesis of acute pancreatitis has not yet been elucidated. We aimed to investigate the effects and the possible mechanism of a new human leukocyte elastase inhibitor (recombinant guamerin) in the treatment of cerulein-induced acute pancreatitis in rats. Methods Fifty Sprague–Dawley rats were divided into three groups: a saline-infused control group (I), a cerulein-induced acute pancreatitis group (II), and a cerulein plus guamerin infusion group (III). Guamerin (1–2 μmol/kg/h) was infused continuously in group III. The severity of pancreatitis was determined biochemically, histologically, and by cytokine changes between groups I, II and III. Results Significant differences in serum amylase, lipase, and pancreatic wet weight were observed in each group, respectively (group I; 2346.2 IU/L, 9.9 IU/L, 1.4 ± 0.3 g, group II; 13,596.8 IU/L, 7439.4 IU/L, 2.2 ± 0.5 g, group III; 9443.2 IU/L, 4516.3 IU/L, 1.7 ± 0.6 g). Serum IL-6 and TNF-α [AU1]level peaked 1–4 h and 1–2 h. After the induction of pancreatitis, IL-6 and TNF-α levels were decreased in group III than group II, (group I; 13.1/4.0 pg/mL, group II; 198.5/63.2 pg/mL, group III; 102.1/13.1 pg/mL), but no significant difference in IL-1β was observed. Histologic gradings and severity, such as vacuolization, inflammation, lobular disarray, and edema of the pancreas, were significantly lower in the cerulein plus guamerin infusion group III. Conclusions Recombinant guamerin, a new human leukocyte elastase inhibitor, may decrease the severity of pancreatitis and diminish pancreatic acinar cell injury by inhibition of neutrophilic infiltration and cytokine activation in the initial stage of cerulein-induced acute pancreatitis in rats.

Changes in the expression and dynamics of SHP-1 and SHP-2 during cerulein-induced acute pancreatitis in rats

Protein tyrosine phosphatases (PTPs) are important regulators of cell functions but data on different PTP expression and dynamics in acute pancreatitis (AP) are very scarce. Additionally, both c-Jun N-terminal kinases (JNK) and extracellular signal-regulated kinases (ERK1/2), together with intracellular cAMP levels in inflammatory cells, play an essential role in AP. In this study we have detected an increase in PTP SHP-1 and SHP-2 in the pancreas at the level of both protein and mRNA as an early event during the development of Cerulein (Cer)-induced AP in rats. Nevertheless, while SHP-2 protein returned to baseline levels in the intermediate or later phases of AP, SHP-1 protein expression remained increased throughout the development of the disease. The increase in SHP-2 protein expression was associated with changes in its subcellular distribution, with higher percentages located in the fractions enriched in lysosomes+mitochondria or microsomes. Furthermore, while the increase in SHP-2 protein was also observed in sodium-taurocholate duct infusion or bile-pancreatic duct obstruction AP, that of SHP-1 was specific to the Cer-induced model. Neutrophil infiltration did not affect the increase in SHP-1 protein, but favoured the return of SHP-2 protein to control levels, as indicated when rats were rendered neutropenic by the administration of vinblastine sulfate. Inhibition of JNK and ERK1/2 with SP600125 pre-treatment further increased the expression of both SHP-1 and SHP-2 proteins in the early phase of Cer-induced AP, while the inhibition of type IV phosphodiesterase with rolipram only suppressed the increase in SHP-2 protein expression during the same phase. Our results show that AP is associated with increases in the expression of SHP-1 and SHP-2 and changes in the dynamics of SHP-2 subcellular distribution in the early phase of Cer-induced AP. Finally, both JNK and ERK1/2 and intracellular cAMP levels are able to modulate the expression of these PTPs.

Adrenomedullin reduces the severity of cerulein-induced acute pancreatitis

We investigated the effect of Adrenomedullin (AM) on cerulein-induced acute pancreatitis in rats. AM treatment (100 ng/kg per rat, subcutaneous) after one hour of cerulein injection reduced the plasma amylase levels, pancreatic weight, pancreatic malondialdehyde (MDA) levels, and the severity of the lesions microscopically. These data suggest that AM has a protective effect on cerulein-induced acute pancreatitis. These could be due to anti-inflammatory properties of AM, inhibition of proinflammatory cytokine secretion, reducing the endothelial permeability increased by reactive oxygen species, endotoxins or cytokines.

Anti-inflammatory actions of perfluorooctanoic acid and peroxisome proliferator-activated receptors (PPAR) α and γ in experimental acute pancreatitis

Perfluorooctanoic acid (PFOA) and agonists of peroxisome proliferator-activated receptors (PPAR) α and γ were investigated for potential anti-inflammatory effects in cerulein-induced acute pancreatitis in rats. PFOA significantly reduced both leukocyte accumulation and prostanoid synthesis. The PPAR-α agonist clofibrate had no effect on leukocyte activation but significantly inhibited prostanoid synthesis whereas the PPAR-γ agonist rosiglitazone significantly reduced leukocyte activation but did not affect synthesis of prostaglandins in the pancreas. Neither PFOA, nor clofibrate or rosiglitazone had an effect on the formation of the inflammatory edema or elevated levels of lipase activity in the blood serum. In summary, PFOA attenuates the accumulation of activated leukocytes and reduces the synthesis of prostanoids in the pancreas during cerulein-induced acute pancreatitis. An activation of PPAR-α causes inhibition of prostanoid synthesis while activation of PPAR-γ inhibits leukocyte activation.

Pathogenic Role of Endothelial Nitric Oxide Synthase (eNOS/NOS-III) in Cerulein-Induced Rat Acute Pancreatitis

Nitric oxide (NO) is a potent pancreatic vasodilator, yet the pathogenic role of NO in acute pancreatitis remains controversial. NO is generated from L-arginine by NO synthase (NOS), classified into three isozymes: neuronal (nNOS), inducible (iNOS), and endothelial NOS (eNOS). The purpose of the present study was to investigate the role of NO/NOS isozymes in the pathogenesis of cerulein-induced acute pancreatitis in rats. Acute pancreatitis was induced in male Wistar rats by two subcutaneous injections of cerulein (20 microg/kg). NG-Nitro-L-arginine methyl ester (L-NAME: a nonselective NOS inhibitor) or aminoguanidine (a relatively selective iNOS inhibitor) was given orally, while tetrahydrobiopterin (BH4), a critical cofactor for NOS, was administered intraperitoneally 30 min before the first cerulein injection. Cerulein given repeatedly twice produced acute pancreatitis, with concomitant increases in the serum amylase level, pancreas weight, myeloperoxidase activity, lipid peroxidation and microvascular permeability. Prior administration of L-NAME, but not aminoguanidine, significantly prevented these changes, in a dose-dependent manner, and this effect was antagonized by the coadministration of L-arginine, a precursor of NO. The expression of dimetric eNOS in the pancreas was markedly suppressed by cerulein injections, together with a decrease in NO production, but the response was partially but significantly reversed by the prior administration of BH4. The increases in the serum amylase level and pancreas weight, as well as the lipid peroxidation induced by cerulein, were significantly attenuated by the administration of BH4. L-NAME had no effect on pancreatic secretion induced by cerulein. These results suggest that the uncoupled eNOS, probably caused by the decrease in endogenous BH4 availability, plays a deleterious role in the pathogenesis of cerulein-induced acute pancreatitis.

Early bacterial infection of the pancreas and course of disease in cerulein-induced acute pancreatitis in rats

Background Bacterial infection of the pancreas aggravates the course of acute pancreatitis. Since bacterial translocation from the gut is likely to be an early event, in an animal model of pancreatitis, we investigated the effect of early bacterial supra-infection of the pancreas on the course of the disease. Methods Six hours after the induction of acute pancreatitis in male Wistar rats ( n = 180) by supramaximal stimulation with cerulein (or placebo in a control group), the animals were operated and a suspension of Helicobacter pylori, Escherichia coli or saline were introduced either in the pancreatic duct or interstitium (12 groups of 15 rats each); after 24 h, animals were killed and the following parameters analysed: macroscopic and histologic appearance of the pancreas (score), wet-to-dry weight ratio, pancreas trypsinogen activation peptide level, serum amylase, interleukin-6 and phospholipase A2 activity. Results All parameters were increased in rats with cerulein-induced pancreatitis in comparison to placebo. Interstitial and intraductal application of bacteria increased the pancreatic damage. This effect was more evident with the application of E. coli in both cerulein and placebo groups. Application of E. coli but not of H. pylori determined pancreatic activation of trypsinogen, increased mortality and induced the production of interleukin-6. Conclusions Bacterial invasion of the pancreas worsens the histologic and clinical picture of disease and induces a systemic inflammatory response.

Ultrastructural clues for the protective effect of melatonin against oxidative damage in cerulein‐induced pancreatitis

The role of oxidative stress has been evaluated in experimental models of acute pancreatitis (AP). The aim of this study is to investigate the effect of melatonin on the ultrastructural changes in cerulein-induced AP in rats. Acute pancreatitis was induced by two i.p. injections of cerulein at 2-hr intervals (50 microg/kg BW). One group received additionally melatonin (20 mg/kg BW) i.p. before each injection of cerulein. The rats were sacrificed 12 hr after the last injection. Pancreatic oxidative stress markers were evaluated by changes in the amount of lipid peroxides and changes in the antioxidant enzyme levels, superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and total glutathione (GSH) levels. Ultrastructural examination was performed using a transmission electron microscope. Formation of numerous, large autophagosomes, mitochondrial damage, dilatation of rough endoplasmic reticulum (RER) and Golgi apparatus, margination and clumping of nuclear chromatin were the major ultrastructural alterations observed in the AP group. Melatonin administration prevented mitochondrial and nuclear changes and dilatation of RER and Golgi apparatus. Rare, small autophagosomes were present within the cytoplasm of some of the acinar cells. Pancreatic damage was accompanied by a significant increase in tissue MDA levels (P < 0.05) and a significant decrease in CAT, SOD, GPx activities and GSH levels (P < 0.005). Melatonin administration significantly reduced MDA levels but increased CAT, SOD, GPx activities and GSH levels (P < 0.005). Melatonin also reduced serum amylase and lipase activities, which were significantly elevated in AP (P < 0.05 and P < 0.005 respectively). These results suggest that oxidative injury is important in the pathogenesis of AP. Melatonin is potentially capable of limiting pancreatic damage produced during AP by protecting the fine structure of acinar cells and tissue antioxidant enzyme activities.

EFFECT OF HYPERTHERMIA ON EXPERIMENTAL ACUTE PANCREATITIS.

Background and Aim: Recent studies indicate that hyperthermia can change inflammatories mechanisms and protects experimental animals from deleterious effects of secretagogue induced pancreatitis. The mechanisms responsible for this protective effect are not known. This present study was designed to evaluated the effects of hyperthermia post-treatment on cerulein-induced acute pancreatitis in rats. Materials and Methods: Acute pancreatitis (AP) was induced in Wistar rats by the administration of two cerulein injections (20 micrograms/Kg SC followed by another 20 micrograms/Kg IV one hour later). After the induction of AP the animals were heated in a cage with two 100W lamps. Body temperature was increased to 39ºC (during 15 minutes) and maintained at that level for 45 minutes. Animals temperature was monitored with a rectal thermometer. Control group animals were also submitted to AP but kept at room temperature thereafter. The rats were killed by exsanguination after the ending of the hyperthermia process. Serum amylase levels were determined and pancreatic edema formation was analyzed through pancreatic wet weight ratio and Evans’ Blue dye extravasation. Pancreatic biopsies were taken for histology study. Results: Hyperthermia post-treatment ameliorated the pancreatic edema, whereas the morfologic damage and the serum amylase level remain unaltered. Control animals had typical edema, serum amylase activity and morphologic changes of this acute pancreatitis model. Conclusions: The findings suggest a beneficial effect of the thermal stress on the inflammatory edema in the cerulein-induced model of experimental AP. Supported by Grant: CNPq.

Protective effect of central thyrotropin-releasing hormone analog on cerulein-induced acute pancreatitis in rats

Central neuropeptides play a role in many physiological functions through the autonomic nervous system. We have recently demonstrated that central injection of a thyrotropin-releasing hormone (TRH) analog increases pancreatic blood flow through vagal and nitric oxide-dependent pathways. In this study, the central effect of a TRH analog on experimental acute pancreatitis was investigated in rats. Acute pancreatitis was induced by two intraperitoneal injections of cerulein (40 μg/kg) at 1-h interval. Either stable TRH analog, RX 77368 (5–100 ng), or saline was injected intracisternally 15 min before the first cerulein injection under ether anesthesia. Serum amylase level was measured before and 5 h after the first cerulein injection. Pancreatic wet/dry weight ratio and histological changes were also evaluated. Intracisternal TRH analog inhibited cerulean-induced elevation of serum amylase level, increase in pancreatic wet/dry weight ratio and pancreatic histological changes, such as interstitial edema, inflammation and vacuolization. The pancreatic cytoprotection induced by central TRH analog was abolished by subdiaphragmatic vagotomy and N G-nitro- l-arginine-methyl ester ( l-NAME), but not by 6-hydroxydopamine (6-OHDA). Intravenous administration of the TRH analog did not influence cerulein-induced acute pancreatitis. These results indicate that the TRH analog acts in the central nervous system to protect against acute pancreatitis through vagal and nitric oxide-dependent pathways.

Activation of nociceptive neurons in T9 and T10 in cerulein pancreatitis

Mechanisms of pain transduction in acute pancreatitis are poorly understood. Increased Fos expression in the spinal cord is a marker of activation of nociceptive neurons. We hypothesized that cerulein pancreatitis leads to increased Fos expression at T9 and T10, which receive sensory input from the pancreas. Rats were injected with cerulein (100 μg/kg, s.c.) or saline carrier (NS). Endpoints at 4, 6, and 10 h were serum amylase, myeloperoxidase activity (MPO), and spinal cord Fos expression (number of immunoreactive nuclei/section dorsal gray matter). Fos-like immunoreactivity (FLI) at T9-T10 was compared to internal controls (T6, T12). An average of 20 spinal cord histologic sections were evaluated per rat. Some animals were injected with the μ-opioid receptor agonist, buprenorphine (90 μg/kg, s.c.), 3 h after cerulein, and their endpoints were measured at 6 h. Analysis of variance and t tests were used for statistical analysis. Results are means ± SEM. As expected, cerulein induced edematous pancreatitis, with a 4-fold increase in serum amylase at 6 h [cer ( n = 8): 14,000 ± 1,300 U/ml versus NS ( n = 10): 3,700 ± 300, P < 0.005)] and a 2-fold increase in MPO activity (0.25 ± 0.05) activity units/dry wt versus 0.13 ± 0.02, P < 0.05). Cerulein induced nearly a 2-fold increase in FLI at T9 and T10 [ n = 10 (cer) and n = 13 (NS): T9, 14 ± 1.5 versus 7.8 ± 0.88; T10, 15 ± 1.7 versus 8.3 ± 0.70; P < 0.05]. Peak effects of cerulein on FLI occurred at 6 h and were greatest at T9/T10 with relative sparing of T6/T12. T6/T12 expression was similar in experimental and control groups. Buprenorphine significantly reduced both serum amylase and FLI and T9/T10. Cerulein-induced acute pancreatitis in rat increases visceral nociceptive signaling at spinal cord levels T9 and T10, with a peak at 6 h. Blockade of this effect by the μ-opioid receptor agonist buprenorphine could occur either by direct activation of central opioid receptors and/or an anti-inflammatory mechanism. FLI is a useful tool for studying the pathophysiology of pain in experimental acute pancreatitis.

Administration of hyaluronic acid and chondroitin-4-sulfate limits endogenous antioxidant depletion and reduces cell damage in experimental acute pancreatitis.

Several reports have described a loss of endogenous antioxidants and molecular oxidative damage during acute pancreatitis. Since hyaluronic acid and chondroitin-4-sulfate possess antioxidant properties, the effect of the administration of these glycosaminoglycans in a cerulein-induced acute pancreatitis in rats was investigated. Cerulein administration produced pancreatic edema and a marked increase in serum lipase and amylase activity; induced a severe depletion of reduced glutathione, catalase, and superoxide dismutase levels; primed lipid peroxidation; and promoted neutrophil intervention. Intraperitoneal pretreatment of rats with hyaluronic acid or chondroitin-4-sulfate or with both compounds ameliorated pancreatic cell conditions; restored the endogenous antioxidants reduced glutathione, catalase and superoxide dismutase; limited cell membrane peroxidation; and reduced neutrophil activation. Our data confirm the antioxidant activity of these 2 glycosaminoglycans.

Nitric oxide protects against pancreatic subcellular damage in acute pancreatitis.

Oxidative stress involvement in damage to the pancreas in acute pancreatitis (AP) is well documented. However, little is known about oxidative damage occurring in the different subcellular fractions of pancreatic cells. The aim of this study was to ascertain the main targets of oxidative damage inside cells after AP and the role of endogenous nitric oxide (NO) in it. A model of cerulein-induced AP in rats was used and N-nitro-l-arginine methyl ester (l-NAME) was administered as an NO production inhibitor. After pancreatitis induction, indicative parameters of lipid peroxidation and protein oxidation together with some enzymatic and nonenzymatic endogenous free radical scavengers were assessed in serum and pancreatic subcellular fractions. In pancreatitic rats, malondialdehyde and protein carbonyl group concentrations were significantly increased (P < 0.05) in serum and some fractions. The increases were higher in l-NAME-treated rats (P < 0.05). Superoxide dismutase and catalase activities were also increased (P < 0.05) but were decreased (P < 0.05) with l-NAME. The alpha-tocopherol concentration diminished (P < 0.05) in serum and all the studied subcellular fractions and the decrease was stronger in l-NAME-treated rats. Our data suggest that microsomes followed by lysosomal + mitochondrial are the fractions most susceptible to oxidative damage in AP. Endogenous NO plays a protective role against oxidative damage to subcellular fractions.

Effects of Taurine on Cerulein-Induced Acute Pancreatitis in the Rat

Taurine, or 2-aminoethane sulfonic acid, is an intracellular amino acid and has been suggested to have a function in protecting biological systems from oxidative tissue damage. The aim of this study was to determine the effect of taurine against cerulein-induced acute pancreatitis in rats. Acute pancreatitis was induced by administering three subcutaneous injections of cerulein (40 µg/kg body weight) at 1-hour intervals, while taurine was administered intravenously at graded doses (30, 100, or 300 mg/kg, respectively) following the first cerulein injection. The severities of pancreatitis and lung injury were determined by measuring biochemical parameters, tissue myeloperoxidase (MPO), and histological changes. To clarify the mechanism of taurine, serum IL-1β and TNF-α levels and tissue concentrations of malondialdehyde (MDA) were evaluated. In cerulein-induced acute edematous pancreatitis, treatment with taurine significantly decreased hyperamylasemia, tissue MPO, pancreatic edema, and the extent of pancreatic and pulmonary injury. Taurine decreased MDA concentration in the pancreas and lung, but not the serum cytokine concentration. We would conclude that taurine has beneficial effects in cerulein-induced acute pancreatitis and lung injuries by preventing the production of oxygen free radicals.

Comparison of the efficacy of the somatostatin analogue SMS 201-995 and electromagnetic fields in cerulein-induced pancreatitis in rats

Background: Despite known protocols, acute pancreatitis still has mortality rates of 10% and morbidity rates of 30%, and research continues into alternative therapeutic models for preventing both the inflammation and the complications of pancreatitis. Objective: This study was undertaken to investigate the effect of electromagnetic field therapy in acute pancreatitis and to compare the effect of electromagnetic fields with that of the somatostatin analogue SMS 201-995 in the treatment of cerulein-induced acute pancreatitis in rats. Methods: Male Wistar rats were divided into 4 equal groups. In group I, cerulein administration was followed by electromagnetic field therapy; group II received only cerulein. In group III (the control group), saline administration was followed by electromagnetic field therapy. In group IV, cerulein administration was followed by SMS 201-995 administration. After the procedure, serum amylase activity was determined for all rats and the pancreas of each rat was assessed histopathologically based on a scoring system in which 0 = no change and 7 = maximum change. A score ≥3 indicates cerulein-induced pancreatitis. Significance was set at P < 0.05. Results: Each group contained 12 rats. Statistically significant differences in pathologic pancreatitis scores were noted between groups I and II ( P < 0.001) and between groups II and IV ( P < 0.001). No other between-group differences were statistically significant. Conclusions: Electromagnetic field therapy appears to be as effective as somatostatin therapy in cerulein-induced acute pancreatitis in this study. It can thus be considered an alternative to somatostatin therapy in the treatment of acute pancreatitis in rats.

Effects of Mast-Cell Stabilization in Cerulein-Induced Acute Pancreatitis in Rats

Acute pancreatitis is characterized by inflammationof the pancreas that ranges from mild inflammationto severe necrotizing pancreatitis (1-3).Several factors can initiate a cascade of pathologic events that results in AP (4). A key feature in thispathogenesis is inflammatory reaction. However,causes of exaggerated inflammatory reaction are notwell understood (4,5). Since the pathogenesis of pancreatitisis still unclear, most of the treatment modalitiesare largely supportive and independent of thepathogenesis (1,2).

Proteases and Protease Inhibitors in Cerulein-Induced Acute Pancreatitis in Rats

Background. Proteases and protease inhibitors are important in acute pancreatitis (AP), although little is known about the time course in cerulein-induced AP in the rat.Materials and methods. AP was induced by supramaximal stimulation of cerulein, 10 μg/kg/h, and during 72 h we measured lipase, amylase, albumin, prekallikrein, factor X, α1-protease inhibitor, α1-macroglobulin, α2-antiplasmin, antithrombin III (all in plasma) and macroscopic and histologic variables.Results. Within 12 h an edematous pancreatitis was evident with peak values of peritoneal exudate, pancreatic wet weight ratio, and plasma amylase and lipase activities. Histologically, edema and vacuolization were prominent already after 3 and 6 h, respectively, while inflammation, necrosis, and total histological score gradually increase to reach peak levels at 48 h. Proenzymes and most plasma protease inhibitors decreased to low levels after 6–12 h followed by a gradual increase. The sequential changes over time indicate that kallikrein - kinin activation, and plasminogen activation are probably early events in cerulein-induced AP in rats. α1-Macroglobulin and α1-protease inhibitor gradually decreased during the whole study period, probably being “second line” defense inhibitors. Levels above normal were seen for α2-antiplasmin and factor X at 48 h, normalizing at 72 h.Conclusions. These results suggest that protease activation and protease inhibitor consumption occur in cerulein-induced AP in the rat.

Melatonin reduces lipid peroxidation and tissue edema in cerulein-induced acute pancreatitis in rats.

Since oxygen free radicals and lipid peroxidation have been implicated in the pathogenesis of an early stage of acute pancreatitis, we examined whether melatonin, a recently discovered free-radical scavenger, could attenuate pancreatic injury in Sprague-Dawley rats with cerulein-induced pancreatitis. Acute pancreatitis was induced by four intraperitoneal injections of cerulein (50 microg/kg body wt) given at 1-hr intervals. Thirty minutes after the last cerulein injection, the rats were killed and the degree of pancreatic edema, the level of lipid peroxidation in the pancreas, and serum amylase activity were increased significantly. Pretreatment with melatonin (10 or 50 mg/kg body wt) 30 min before each cerulein injection resulted in a significant reduction in pancreatic edema and the levels of lipid peroxidation. Serum amylase activity, however, was not significantly influenced by either dose of melatonin. Moreover, we found that cerulein administration was associated with stomach edema as well as high levels of lipid peroxidation in the stomach and small intestine, which were also reduced by melatonin. Melatonin's protective effects in cerulein-treated rats presumably relate to its radical scavenging ability and to other antioxidative processes induced by melatonin.