Sphincter of Oddi dysfunction produces acute pancreatitis in the possum

BACKGROUND: Sphincter of Oddi dysfunction has been implicated as a cause of various forms of acute pancreatitis. However, there is no direct evidence to show that sphincter of Oddi dysfunction can cause obstruction of trans-sphincteric flow resulting in acute pancreatitis. AIMS: To determine if induced sphincter of Oddi spasm can produce trans-sphincteric obstruction and, in combination with stimulated pancreatic secretion, induce acute pancreatitis. METHODS: In anaesthetised possums, the pancreatic duct was ligated and pancreatic exocrine secretion stimulated by cholecystokinin octapeptide/secretin to induce acute pancreatitis. In separate animals, carbachol was applied topically to the sphincter of Oddi to cause transient sphincter obstruction. Sphincter of Oddi motility, trans-sphincteric flow, pancreatic duct pressure, pancreatic exocrine secretion, plasma amylase levels, and pancreatic tissue damage (histology score) were studied and compared with variables in ligation models. RESULTS: Acute pancreatitis developed following stimulation of pancreatic exocrine secretion with peptides after pancreatic duct ligation (p<0.05). Neither pancreatic duct ligation nor stimulation of pancreatic exocrine secretion with cholecystokinin octapeptide/secretin alone resulted in acute pancreatitis. Topical carbachol stimulated sphincter of Oddi motility abolished trans-sphincteric flow, and increased pancreatic exocrine secretion (p<0.05) and pancreatic duct pressure to levels comparable with pancreatic duct ligation (p<0.001). Carbachol application (with or without combined peptide stimulation) elevated plasma amylase levels (p<0.01) and produced pancreatic tissue damage (p<0.05). Decompression of pancreatic duct ameliorated these effects (p<0.05). CONCLUSION: Induced sphincter of Oddi dysfunction when coupled with stimulated pancreatic secretion causes acute pancreatitis. This may be an important pathophysiological mechanism causing various forms of acute pancreatitis.     

Severe acute pancreatitis and reduced acinar cell apoptosis in the exocrine pancreas of mice deficient for the Cx32 gene

BACKGROUND & AIMS: The early events leading to acinar cell injury during acute pancreatitis are poorly characterized. Signaling through gap junction channels contributes to the homeostasis of the exocrine pancreas by coordinating acinar cell activity within an acinus. To explore the role of gap junctional communication in acinar cell response to injury, we analyzed the course of acute pancreatitis induced by injection of cerulein in mice deficient for Cx32, the major gap junction protein expressed in the exocrine pancreas. METHODS: The severity of pancreatitis was evidenced by measuring serum amylase activity, pancreatic edema, acinar cell necrosis, pancreatic tumor necrosis factor alpha concentration, and myeloperoxidase activity. Acinar cell apoptosis was detected by terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling (TUNEL), caspase-3 activity, and Bax/Bcl-2 expression. Expression and function of connexin were evaluated by immunofluorescence and dye coupling. RESULTS: Cx32-deficient mice exhibited a deleterious course of acute pancreatitis with increased necrosis, edema, and inflammation of the exocrine pancreas. In addition, the exocrine pancreas of Cx32-deficient mice showed a decreased number of TUNEL-positive acinar cells and decreased caspase-3 activity but no change in Bax or Bcl-2 pancreatic expression. Interestingly, chemicals known to induce apoptosis in vivo had no effect on Cx32-deficient pancreatic acinar cells. CONCLUSIONS: Deficiency of a pancreatic connexin converts a mild reversible form of acute pancreatitis into a severe disease and decreases the sensitivity of acinar cells to apoptotic stimuli. The results show that acinar cell-to-cell communication plays a key role in the modulation of severity of acute pancreatitis.     

Protective effects of rhubarb on experimental severe acute pancreatitis

AIM: To investigate the effects of rhubarb on severe acute pancreatitis (SAP) in rats. METHODS: Severe acute pancreatitis was induced by two intraperitoneal injections of cerulein (40 μg/kg body weight) plus 5-h restraint water-immersion stress. Rhubarb (75-150 mg/kg) was orally fed before the first cerulein injection. The degree of pancreatic edema, serum amylase level, local pancreatic blood flow (PBF), and histological alterations were investigated. The effects of rhubarb on pancreatic exocrine secretion in this model were evaluated by comparing with those of somatostatin. RESULTS: In the Cerulein+Stress group, severe edema and diffuse hemorrhage in the pancreas were observed, the pancreatic wet weight (11.60&#177;0.61 g/Kg) and serum amylase (458 490&#177;43 100 U/L) were markedly increased (P&lt;0.01 vs control). In the rhubarb (150 mg/kg) treated rats, necrosis and polymorphonuclear neutrophil (PMN) infiltration in the pancreas were significantly reduced (P&lt;0.01), and a marked decrease (50%) in serum amylase levels was also observed (P&lt;0.01). PBF dropped to 38% (93&#177;5 mL/min per 100 g) of the control in the Cerulein+Stress group and partly recovered in the Cerulein+Stress+Rhubarb 150 mg group (135&#177;12 mL/min per 100 g) (P&lt;0.01). The pancreatic exocrine function was impaired in the SAP rats. The amylase levels of pancreatic juice were reduced in the rats treated with rhubarb or somatostatin, comparing with that of untreated SAP group. The bicarbonate concentration of pancreatic juice was markedly elevated only in the rhubarbtreated group (P&lt;0.01). CONCLUSION: Rhubarb can exert protective effects on SAP, probably by inhibiting the inflammation of pancreas, improving pancreatic microcirculation, and altering exocrine secretion.     

Pancreatic exocrine function in unconscious rats treated with submaximal, maximal, and supramaximal doses of bombesin tetradecapeptide

Supramaximal stimulation of the rat pancreas in vivo with caerulein elicits a sharp decline in pancreatic juice volume and protein outputs and initiates acute edematous pancreatitis within 30 min. Because of the similar effects of caerulein and bombesin on pancreatic exocrine function, we examined in unconscious rats (a) the effects of a continuous, 4-h intravenous infusion of varying doses (0.2-40.0 nmol/kg/h) of bombesin on pancreatic juice volume and protein output, and (b) whether supramaximal doses of bombesin produce acute edematous pancreatitis. A maximal, fivefold and 17-fold rise in pancreatic juice volume and protein output was achieved with intravenous doses of 1.0 and 4.0 nmol of bombesin/kg/h, respectively. Pancreas weights in rats infused with bombesin as high as 40.0 nmol/kg/h were not significantly different from control animal values (no bombesin infusion) and serum amylase concentrations were only moderately (twofold) elevated over control values in rats i.v. infused with 4.0-40.0 nmol of bombesin/kg/h. The pancreas in rats treated with the highest dose of bombesin (40.0 nmol/kg/h) revealed sparsely scattered microvacuoles in a few acinar cells and minor evidence of interacinar edema. It is concluded that supramaximal stimulation of the rat pancreas in vivo with bombesin fails to elicit acute edematous pancreatitis and appears to be related to the ability of bombesin, in contrast to supramaximal doses of caerulein, to continuously stimulate maximal pancreatic juice secretion.     

Pseudomonas pneumonia-mediated sepsis induces expression of pancreatitis-associated protein-I in rat pancreas

Severe impairment of exocrine pancreatic secretion has recently been demonstrated in a clinical study in sepsis and septic shock patients. The purpose of this study was to further evaluate involvement of the pancreas in the acute phase reaction in sepsis. Using a normotensive rat model of Pseudomonas pneumonia-induced sepsis, we assessed the expression of PAP-I, amylase and trypsinogen mRNA, PAPI protein levels, and cytokine expression in the pancreas by Northern and Western blot analysis and RT-M PCR, respectively. Presence of several well-established features of pancreatitis in sepsis-induced animals were examined by biochemical and histopathological methods as well as by a determination of both water and myeloperoxidase content. Sepsis resulted in an up-regulation of PAP-I gene expression and increase in its protein level in pancreas while the mRNA levels of amylase and trypsinogen were down-regulated. Differences in the pancreatic cytokine expression, serum amylase and serum lipase levels, the occurrence of pancreatic edema as well as the severity of inflammatory infiltration and necrosis were not significantly different between sham and pneumonia groups. Acinar cells showed increased vacuolization in pneumonia animals 24 hours after the treatment. These findings demonstrate that the pancreas is actively involved in the acute phase reaction in sepsis of remote origin. This involvement occurs without concomitant biochemical and histopathologic alterations observed in pancreatitis. Taken all together, these features are indicative of a sepsis-specific dysfunction of the pancreas.     

Dual effects of hydrocortisone on exocrine rat pancreas

The acute and chronic effects of hydrocortisone on exocrine pancreatic function were examined in the isolated perfused rat pancreas. In the first part of this study, rats were given subcutaneous injections of hydrocortisone at doses of 1.25, 2.5, 5, and 10 mg/kg body wt once daily for 7 days. Trypsin and lipase secretion in response to 100 pM cholecystokinin-octapeptide was significantly increased in rats with the two highest doses of hydrocortisone compared with controls, irrespective of whether calculated as the total amount of stimulated output of enzymes or related to the secretion of enzyme to the pancreas content. On the other hand, the secretory responsiveness of amylase to 100 pM cholecystokinin-octapeptide was maximal at the 5-mg dose, and decreased with higher doses. In the second part, 100 microM hydrocortisone was superimposed for 20 min on 100 pM cholecystokinin-octapeptide stimulation to examine the acute effects of hydrocortisone on exocrine pancreatic function in the isolated perfused rat pancreas. Addition of hydrocortisone caused a significant inhibition of the secretion of pancreatic juice and amylase. The present study has clearly demonstrated the dual effects of glucocorticoids on the pancreas: inhibition and potentiation. There is a possibility that chronic treatment with large doses of glucocorticoid may sensitize the acinar cells an induce hypersecretion of trypsin and lipase, whereas acute treatment inhibits secretory function of exocrine pancreas.     

Protection by gabexate mesilate (FOY) of the exocrine pancreas in rats with acute pancreatitis induced by a supramaximal dose of caerulein

Earlier studies have reported that interstitial oedematous pancreatitis characterized by hyperamylasaemia can be seen during the early stage of stimulation of supramaximal dose of caerulein. The present study investigated the changes in both cellular and lysosomal fragility and the protective effects of a synthetic protease inhibitor gabexate mesilate (FOY) on this non-invasive model of experimental pancreatitis. The infusion of FOY (50 mg/kg/h) prevented the caerulein-induced increase in serum amylase and pancreatic oedema formation and reduced the elevated amylase content significantly. The administration of FOY with caerulein also reduced the increased lactic dehydrogenase (LDH) discharge significantly and inhibited the cathepsin B leakage from lysosomes in an in vitro incubation system. These results indicate that FOY plays its protective role at the subcellular level--that is, in lysosomes by inhibiting some proteases such as phospholipase A2. The importance of esterases in the pathogenesis of acute pancreatitis is demonstrated. This type of esterase inhibitor may be valuable clinically in the treatment of acute pancreatitis and these results also suggest the role of lysosomal fragility in the pathogenesis of progression of acute pancreatitis.     

Leukotriene receptor antagonism in experimental acute pancreatitis in rats

OBJECTIVES: Acute pancreatitis is a multifactorial disease caused by activation of several inflammatory mediators. Leukotrienes, beside other mediators, may be involved in acute pancreatitis. The aim of this study was to investigate the effects of 'zafirlukast', a leukotriene receptor antagonist, in acute pancreatitis and its relation with prostaglandin synthesis. METHODS: Eighty rats were randomly divided into eight groups. Acute pancreatitis was induced by subcutaneous injection of cerulein (20 microg/kg), four times at 1-h intervals. Zafirlukast (20 mg/kg) was applied intraperitoneally as a pretreatment. Prostaglandin synthesis was inhibited by low-dose indomethacin (5 mg/kg subcutaneously). Pancreatic histopathology, serum amylase activity and pancreatic myeloperoxidase activity were determined to assess the severity of pancreatitis. RESULTS: Zafirlukast pretreatment alone did not induce any inflammation and fatty necrosis in pancreatic tissue. However, it increased the histopathological score from 3.70 +/- 0.57 to 6.62 +/- 0.53 in rats with acute pancreatitis (P < 0.001). Fatty necrosis was especially prominent in the zafirlukast-treated acute pancreatitis group compared with the untreated group (2.62 +/- 0.26 versus 0.40 +/- 0.22, respectively; P < 0.001). Inhibition of prostaglandin synthesis by indomethacin partially suppressed the harmful effects of zafirlukast in acute pancreatitis. It decreased the pathological score (4.62 +/- 0.73) and fatty necrosis (1.50 +/- 0.32) in that group. CONCLUSION: Interestingly, leukotriene receptor antagonism by zafirlukast increased the pancreatic histopathological score and fatty necrosis in rats with acute pancreatitis. Blocking of cysteinyl leukotriene receptors might cause an induction of mediator synthesis via other pathways. Effects of leukotriene receptor antagonism on the pancreas must be evaluated extensively in further studies.     

Pancreatic exocrine function during acute exacerbation in WBN/Kob rats with spontaneous chronic pancreatitis

Summary Conclusion Pancreatic exocrine hypofunction is markedly deteriorated during acute exacerbation in a rat model with chronic pancreatitis. Background Little is known about pancreatic exocrine function during acute exacerbation in patients with chronic pancreatitis. We investigated changes in pancreatic exocrine function after inducing acute pancreatitis in an animal model of spontaneous chronic pancreatitis. Methods WBN/Kob rats with chronic pancreatitis sequentially underwent pancreatic exocrine function test 1–6 d after surgical preparation with external pancreatic fistula. We induced acute pancreatitis in another WBN/Kob rats by iv administration of cerulein at a rate of 10 μg/kg/h for 4 h 4 after surgical preparation. Pancreatic exocrine function test was undertaken in a conscious state 1 d before and after cerulein administration. Results In WBN/Kob rats not given cerulein, pancreatic exocrine function remained almost constant, at 3–6 d after surgery. Marked hyperamylasemia developed immediately after cerulein administration. After its administration, the pancreas microscopcially showed prominent intersitial edema and intracellular vacuolization of acinar cells in addition to the finding of pre-existing chronic pancreatitis. Basal and chole-cystokinin-stimulated flow rate, bicarbonate output, and protein output, which were substantially impaired 1 d before cerulein administration, were further reduced 1 d after its administration.     

The effects of somatostatin on the microperfusion of the pancreas during acute necrotizing pancreatitis in rats

BACKGROUND/AIMS: Autodigestion and impairment of microcirculation of the pancreas play an important role in the pathogenesis of acute pancreatitis. Somatostatin with the reducing effect on the hepato-splanchnic blood flow decreases exocrine pancreatic secretion. Microcirculatory changes are central to the pathogenesis of acute pancreatitis. However, little is known about the effects of somatostatin on the pancreatic tissue oxygen pressure and acinar cell injury during acute pancreatitis. The aim was to evaluate somatostatin by measuring its effect on the pancreatic tissue oxygen pressure and acinar injury in acute pancreatitis. METHODOLOGY: Acute necrotizing pancreatitis was induced in rats by standardized intraductal bile acid infusion and cerulein hyperstimulation. Serum trypsinogen activation peptide was measured to verify comparable disease severity. After the induction of acute necrotizing pancreatitis, animals randomly received either ringer lactate or somatostatin. Monitoring included cardiorespiratory parameters, hematocrit, amylase, pancreatic tissue oxygen pressure, and trypsinogen activation peptide levels. At the end of the experiments the pancreas was removed for evaluation of acinar cell injury. RESULTS: The two study groups were comparable with regard to mean arterial pressure, heart rate, arterial blood gases, hematocrit, and serum amylase. The induction of pancreatitis resulted in the significant decrease of pancreatic tissue oxygen pressure in both groups. The use of somatostatin did not increase pancreatic tissue oxygen pressure. There were no significant differences in plasma trypsinogen activation peptide and serum amylase levels in the animals of two treatment groups. Only somatostatin decreased pancreatic damage significantly. CONCLUSIONS: The use of somatostatin did not improve pancreatic microcirculation or trypsinogen activation peptide level in acute necrotizing pancreatitis; however, it reduced pancreatic damage. Therefore, it has a limited value in the treatment of the acute pancreatitis.     

Gabexate mesilate (FOY) protects against ceruletide-induced acute pancreatitis in the rat

Acute pancreatitis (AP) is believed to result from intraparenchymal activation of trypsin and other digestive enzymes within the pancreas followed by autodigestion of the gland. Gabexate mesilate (FOY), a synthetic guanidino acid ester exhibiting potent and versatile inhibitory actions on a number of proteinases (e.g., trypsin, kallikrein, C1-r, C1 esterase, plasmin, thrombin, phospholipase A2), was examined for its ability to protect the rat pancreas against development of AP induced by pharmacological doses of ceruletide (CRT). Rats were i.v. infused for 6 h with either CRT (5 micrograms/kg/h) or CRT + FOY (50 mg/kg/h). In FOY-treated rats the serum amylase and trypsinogen concentrations were reduced by 60 and 80%, respectively, compared to rats infused with CRT alone. Histologically, the extent of acinar cell vacuolization in the pancreas was significantly reduced and interstitial edema, although not assessed by quantitative morphometric techniques, appeared to be qualitatively lessened in the FOY-treated rats. The ability of FOY to inhibit significantly AP produced by supramaximal doses of CRT, coupled with its inhibitory properties on components of the coagulation and complement cascades, stress the importance of continued research on this compound as a potential therapeutic agent for treatment of AP and its systemic sequelae.     

Somatostatin therapy of acute experimental pancreatitis.

Because somatostatin (SRIF) reduces exocrine pancreatic secretion, its effect on acute pancreatitis was investigated in rats. Linear SRIF reduced serum amylase and lipase but had no effect on pancreatic necrosis, oedema, leucocyte infiltration, and enzyme content. The mortality rate was not reduced. These results do not recommend the use of SRIF in the treatment of acute pancreatitis.     

Melatonin reduces apoptosis and necrosis induced by ischemia/reperfusion injury of the pancreas

The pancreas is highly susceptible to the oxidative stress induced by ischemia/reperfusion (IR) injury leading to the generation of acute pancreatitis. Melatonin has been shown to be useful in the prevention of the damage by ischemia-reperfusion in liver, brain, myocardium, gut and kidney. The aim of the study was to evaluate the cytoprotective properties of melatonin against injury induced by IR in pancreas. The obstruction of gastro-duodenal and inferior splenic arteries induced pancreatic IR in male Wistar rats. Melatonin was intraperitoneally administered before or/and after IR injury. The animals were killed at 24 and 48 hr after reperfusion and there were evaluated parameters of oxidative stress (lipoperoxides, superoxide dismutase, catalase, glutathione peroxidase and reduced glutathione), glandular endocrine and exocrine function (lipase, amylase, insulin) and cell injury (apoptosis and necrosis). The IR induced a marked enhancement of oxidative stress and impaired pancreatic function. The histological analysis showed that IR induced acute pancreatitis with the accumulation of inflammatory infiltrate, disruption of tissue structure, cell necrosis and hemorrhage. Melatonin administration before or after pancreatic IR prevented all tissue markers of oxidative stress, biochemical and histological signs of apoptosis and necrosis, and restored glandular function. No histological signs of pancreatitis were observed 48 hr after reperfusion in 80% of the animals treated with melatonin, with only a mild edematous pancreatitis being observed in the remaining rats. Preventive or therapeutic administration of melatonin protected against the induction of oxidative stress and tissue injury, and restored cell function in experimental pancreatic IR in rats.     

Effect of Pancreatic Stimulation on Serum and Urine Amylase Isoenzymes in Man

Alpha amylase of pancreatic origin is cleared by the kidney more rapidly than the salivary isoamylase. To determine whether alterations in the ratio of pancreatic to salivary amylase in sera caused alterations in over all renal clearance, the clearance of amylase was measured before and after the exocrine pancreas was stimulated with a prolonged intravenous infusion of secretin plus cholecystokinin. Serum and urine samples collected prior to and following stimulation were analyzed for amylase activity and creatinine concentration. Amylase isoenzymes were separated using isoelectric focusing. Over all renal clearance of amylase and of the separated amylase isoenzymes were calculated as a percentage of the clearance of creatinine. The hormone infusion was associated with an increase in serum and urine amylase activities, this increase being mainly accounted for by pancreatic amylase. The renal clearance of the salivary and pancreatic isoamylases was not altered by the hormone infusion but the over all amylase clearance by the kidney rose from 2.31 +/- 0.74 to 3.42 +/- 1.46% of creatinine clearance. In some cases the renal clearance of amylase following stimulation entered the range considered diagnostic for acute pancreatitis.     

Ceruletide-induced acute pancreatitis in the dog and its amelioration by exogenous secretin

Large pharmacological doses of ceruletide administered to conscious dogs by intravenous (i.v.) infusion uniformly induce a severe acute necrotizing pancreatitis within 4 h. High-dose i.v. secretin administered for a period of 24 h after cessation of ceruletide infusion resulted in a significant amelioration of the acute pancreatitis compared to non-secretin-treated dogs with acute pancreatitis. Light microscopy of the pancreas in secretin-treated dogs revealed a significant decrease in edema, polymorphonuclear leukocyte infiltration, cell necrosis and acinar cell vacuolization. Serum amylase levels in secretin-treated dogs were significantly decreased compared to non-secretin-treated dogs. The results of this study suggest that high-dose i.v. secretin exerts a beneficial effect on pre-established, ceruletide-induced acute pancreatitis in dogs.     

Ceruletide-induced acute pancreatitis in the dog and its amelioration by exogenous secretin

Summary Large pharmacological doses of ceruletide administered to conscious dogs by intravenous (i.v.) infusion uniformly induce a severe acute necrotizing pancreatitis within 4 h. High-dose i.v. secretin administered for a period of 24 h after cessation of ceruleetide infusion resulted in a significant amelioration of the acute pancreatitis compared to non-secretin-treated dogs with acute pancreatitis. Light microscopy of the pancreas in secretin-treated dogs revealed a significant decrease in edema, polymorphonuclear leukocyte infiltration, cell necrosis and acinar cell vacuolization. Serum amylase levels in secretin-treated dogs were significantly decreased compared to non-secretin-treated dogs. The results of this study suggest that high-dose i.v. secretin exerts a beneficial effect on pre-established, ceruletide-induced acute pancreatitis in dogs.     

Pancreatic exocrine secretion in acute experimental pancreatitis

Little is known about exocrine pancreatic secretory function in patients with acute pancreatitis, in particular during the early phase of the disease. Therefore, this study evaluates basal and stimulated pancreatic secretion in vivo and in vitro in four different models of acute pancreatitis which reflect its clinical spectrum of severity: (a) edematous pancreatitis induced in the rat by seven IP injections of 50 micrograms/kg cerulein at hourly intervals; (b) edematous pancreatitis with cellular necrosis induced in the mouse by seven IP injections of 50 micrograms/kg cerulein at hourly intervals; (c) hemorrhagic pancreatitis induced in the mouse by feeding an ethionine-supplemented, choline-deficient diet for 66 hours; and (d) hemorrhagic pancreatitis induced in the rat by retrograde infusion of 0.6 mL 5% sodium taurocholate into the pancreatic duct. Secretory studies were performed in vivo and in vitro at various times after onset of pancreatitis. The results show that the exocrine pancreas gradually became resistant to cholecystokinin stimulation after the onset of acute pancreatitis in all four animal models. Cholecystokinin-stimulated secretion was almost abolished in vivo and in vitro at the time of maximal histological damage. In vivo basal secretion was also reduced. In vitro there was an increase in basal release of amylase from isolated acini that was not caused by an increase in luminal secretion but by enzyme release from damaged cells. The time course of improvement of secretory function after acute experimental pancreatitis depended on the severity of the pancreatitis. Recovery of secretory capacity took longer after severe necrotizing pancreatitis than after edematous pancreatitis. However, the ultimate resolution of secretory function was remarkable, in particular after severe hemorrhagic pancreatitis. In all four models, secretory capacity became indistinguishable from normal before the morphological alterations had completely resolved. The present experimental data suggest that pancreatic secretion, and particularly pancreatic secretory response to cholecystokinin, may also be reduced in patients early after the onset of acute pancreatitis.     

Comparative inhibitory effects of pirenzepine and atropine on cholinergic stimulation of exocrine and endocrine rat pancreas

The effects of pirenzepine on carbamylcholine-stimulated exocrine and endocrine pancreatic functions were compared with those of atropine in both the isolated pancreatic acini and the isolated perfused pancreas of rats. In the isolated acini pirenzepine and atropine produced a concentration-dependent inhibition of amylase secretion initiated by carbamylcholine. This inhibition resulted in a rightward shift in the dose-response curve for carbamylcholine-stimulated amylase secretion without altering the maximal increase in amylase secretion. Pirenzepine was, however, approximately 300 times less potent than atropine in inhibiting the stimulated amylase release. A similar difference in potency was observed with respect to carbamylcholine stimulation of pancreatic juice, amylase, and insulin release from the isolated perfused pancreas. The maximal inhibitory concentration of pirenzepine on a maximal effective concentration of pirenzepine on a maximal effective concentration of carbamylcholine for stimulating pancreatic exocrine secretion was 10 microM, whereas that of atropine was 30 nM. The present data define the pirenzepine receptors in the exocrine and endocrine pancreas as low-affinity-type receptors.     

Effects of somatostatin on acute canine experimental pancreatitits

Summary Somatostatin is an inhibitory hormone that decreases the secretion and end organ response of cholecystokinin (CCK). Inhibition of hormonal stimulation of pancreatic exocrine secretion by somatostatin may improve the course of acute pancreatitis. Anesthetized dogs underwent cholecystectomy and cannulation of the pancreatic duct, thoracic, duct, and portal vein. Twenty experiments were performed in random order with 5 dogs in each group. Hourly measurements of lymph flow and portal and thoracic duct amylase were made. Portal blood insulin, glucagon, and CCK concentrations were determined by radioimmunoassay on samples obtained at the beginning and end of the experiments. Pancreatitis was induced by injecting, under, constant pressure, 10 ml bile into the pancreatic duct during 1 min. Somatostatin was administered intravenously (20 μg/kg/hr). After 5 h, the dogs were killed, pancreas glands removed and weighted and tissue samples obtained for histologic evaluation. There was a significant-increase in lymph amylase output and portal venous amylase and CCK concentrations in the dogs with pancreatitis compared to the control dogs. In dogs with pancreatitis, lymphatic amylase secretion and portal CCK concentrations were significantly decreased by somatostatin. Somatostatin did not significantly alter portal amylase concentrations, pancreas gland weights or histologic inflammation when compared to values from dogs with pancreatitis not treated with somatostatin. In bile-induced acute experimental pancreatitis, somatostatin decreases thoracic duct amylase output and may have a protective influence on the course of pancreatitis.     

Experimental pancreatitis induced by synthetic prooxidant tert-butyl hydroperoxide

The purpose of this study was to verify whether injection of tert-butyl hydroperoxide (Bu(t)OOH, a well-known prooxidant agent) into the bile-pancreatic duct can induce acute pancreatitis. A rapid blockade of the secretion was observed in the majority of the animals after 3 hours of observation. After 6 hours, the secretion reached a very low level, significantly different compared with controls. In groups of rats injected with Bu(t)OOH, pancreatic weight gain was observed compared with the rats injected with physiologic saline. Histology of pancreata removed 3 hours after injection of Bu(t)OOH showed acinar cell vacuolization, interstitial edema, focal necrosis of pancreatic acini, fat-tissue necrosis, and leukocyte infiltration of the organ. These changes were considerably greater after the 6-hour observation period. Electron-microscopic inspection revealed profound morphologic changes 3 hours after Bu(t)OOH injection. The control rats receiving physiologic saline alone had well-preserved pancreatic tissue structure. In conclusion, injection of the prooxidant agent, tert-butyl hydroperoxide, into common bile-pancreatic duct induces acute necrotizing pancreatitis, which indicates the crucial role of free radical reactions in pathogenesis of this disease.