Faculty Bibliography

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.

In most patients presenting with acute pancreatitis, the cause can be established on the basis of initial history, physical examination, laboratory studies, and abdominal sonography. Patients with unexplained pancreatitis at that point are often considered to have idiopathic disease. However, a cause and, often, effective treatment to prevent recurrent pancreatitis are possible in many of these patients if an aggressive diagnostic approach is taken to discover undiagnosed hyperlipidemia, occult gallstones, abnormalities of the bile and pancreatic ducts, sphincter of Oddi dysfunction, pancreatic cancer and other tumors, and cystic fibrosis (in children and young adults).

This study evaluated the effects of long-term cholecystokinin (CCK) stimulation and blockade on pancreatic and intestinal growth, function, and morphology. CCK release was induced by feeding of the protease inhibitor camostate and CCK blockade by feeding of the CCK antagonist CR 1409. Four groups of NMRI-mice received the following diets for 9 months (each group consisting of 36 mice): (1) chow (control); (2) chow + 100 mg/kg/day camostate; (3) chow + 50 mg/kg/day CR 1409; (4) chow + 100 mg/kg/day camostate + 50 mg/kg/day CR 1409. Long-term feeding of camostate greatly increased pancreatic weight by induction of marked hypertrophy (increase in protein content) and moderate hyperplasia (increase in DNA content). Camostate feeding also increased secretory capacity of the exocrine pancreas. Despite camostate-induced growth neither hyperplastic nor neoplastic nodules developed. The CCK-antagonist CR 1409 markedly inhibited the effects of camostate which are therefore mainly mediated by CCK. Neither long-term CCK stimulation nor CCK blockade altered morphology or composition of duodenal mucosa. Feeding of CR 1409 alone (i.e., without camostate) slightly but significantly decreased pancreatic content of protein and secretory capacity of enzymes when compared to the chow-fed control; pancreatic weight and DNA content remained unchanged after long-term administration of CR 1409. Thus, long-term, continuous and effective blockade of the CCK-receptor only slightly inhibited pancreatic growth and secretory capacity. CCK is, therefore, not an essential growth factor for the pancreas, although increases of endogenous CCK stimulate pancreatic growth and secretory capacity.

The present experiments evaluate in vivo effects of recently described cholecystokinin (CCK) receptor antagonists on rat pancreatic secretion. Pancreaticobiliary secretion was studied after bile duct cannulation in anesthetized rats. After two basal 10-min fractions were selected, secretion was stimulated by intravenous caerulein (0.1-30.0 micrograms/kg) or secretin, and collected for seven further 10-min fractions. Peptide antagonists (CR 1409, CR 1392, and CR 1505) and nonpeptide antagonists (asperlicin and L364,718) were given intravenously 10 min before agonists. Increasing doses of antagonists gradually reduced secretion of protein and enzymes stimulated by submaximal and maximal doses of caerulein. The antagonists did not alter nonstimulated or secretin-stimulated secretion, indicating their specificity for the CCK receptor. Except for proglumide and asperlicin, all antagonists were able to abolish caerulein-stimulated pancreatic secretion, as evaluated by the mean integrated 1-h response to a near-maximal dose of caerulein. The caerulein dose-response curve was gradually shifted to the right by increasing doses of CR 1409, indicating competitive-like kinetics. Inhibition of secretion due to supramaximal doses of caerulein, however, could be reversed by doses of CR 1409 smaller than expected from extrapolating truely competitive kinetics from an in vitro situation to the in vivo situation. The rank order of potency of the compounds to antagonize caerulein-stimulated secretion in vivo agreed with their relative potencies to antagonize caerulein-stimulated amylase secretion from pancreatic acini in vitro as well as with their affinity to bind to peripheral CCK receptors in vitro.(ABSTRACT TRUNCATED AT 250 WORDS)

The appearance of vacuoles inside acinar cells characterizes an early stage of development in different models of acute pancreatitis and, possibly, also in human disease. The vacuoles have been shown to contain both digestive and lysosomal enzymes. This abnormal admixture may have important implications for the pathogenesis of pancreatitis because the lysosomal enzyme cathepsin B can activate trypsinogen and may, by this way, trigger pancreatic autodigestion. For the activation process of trypsinogen by cathepsin B, however, an acidic pH is required. This study, therefore, looked for evidence of vacuole acidification in two different models of acute pancreatitis. Edematous pancreatitis was induced in rats by hyperstimulation with cerulein and hemorrhagic pancreatitis was induced in mice by feeding a choline-deficient, ethionine-supplemented diet. Pancreatic acinar cells were isolated at different times after induction of pancreatitis and incubated with 50 microM of acridine orange to identify acidic intracellular compartments. As shown in previous work, zymogen granules are the main acidic compartment of normal acinar cells; they remained acidic throughout the course of pancreatitis in both models. Vacuoles became increasingly more frequent in both models as pancreatitis progressed. Throughout development of pancreatitis, vacuoles accumulated acridine orange indicating an acidic interior. Addition of a protonophore (10 microM monensin or 5 microM carbonyl cyanide m-chlorophenylhydrazone [CCCP] or a weak base (5 mM NH4Cl) completely and rapidly abolished acridine orange fluorescence inside both zymogen granules and vacuoles providing further evidence for an acidic interior. The acidification of vacuoles seen in two different models of pancreatitis may be an important requirement for activation of trypsinogen by cathepsin B and thus for the development of acute pancreatitis.

In this study we evaluated the effects of hydration, oxygenation, peritoneal lavage, and the protease inhibitor gabexate mesilate in acute hemorrhagic pancreatitis induced by feeding mice a choline-deficient, ethionine-supplemented diet. Different groups of mice were kept at various concentrations of O2 (21%, 35%, and 45% O2), or were treated by either s.c. injections or i.p. injections of electrolyte solution at various doses (0, 4, 6, or 8 ml/day). Further groups were treated either with i.p. lavage, lavage with 1.5 mg/ml of gabexate, or i.p. injections of 100 mg/kg of gabexate without lavage. The potential benefits of the various regimens were assessed by measuring survival, various biochemical and histologic features, and alterations in hematocrit, pH, and blood gases. Increasing O2 concentrations reversed hypoxemia and acidosis, but had no effect on biochemical or morphologic alterations and did not improve survival. However, hydration by s.c. fluid markedly improved survival and normalized the hematocrit without having major effects on biochemical or morphologic alterations. Intraperitoneal fluid did not improve survival. Gabexate injections without lavage had a slight effect on survival and serum amylase concentration and very little effect on histology. Lavage without gabexate had a greater effect on survival, serum amylase, and histology. Addition of gabexate to the lavage fluid increased the beneficial effect of lavage. Increases in amylase and activated trypsin in ascites were markedly reduced by lavage and even more so by lavage with addition of gabexate. We conclude that sufficient hydration appears to be an important factor in supportive care for severe acute pancreatitis, whereas oxygenation without sufficient hydration has no major benefit. Peritoneal lavage with gabexate showed the greatest benefit of the various regimens for acute severe pancreatitis and is worthy of clinical trials.

Seventy-four medical and surgical patients having a minimum of two risk factors for stress-related gastric mucosal bleeding were prospectively selected randomly to receive prophylaxis by antacid titration (to maintain a gastric pH of more than 4) or with sucralfate suspension (1 g/10 ml every four hours). Gastric aspirates were monitored every two hours for pH and overt and occult bleeding. Despite a significantly greater severity of illness in the sucralfate group (p less than 0.01), no significant difference in overt or occult bleeding between the groups could be demonstrated. Low-grade occult blood loss occurred frequently in both groups, but only one of the 74 patients (four risk factors, sucralfate group) had significant stress-related bleeding as defined by preset criteria and documented by endoscopy. The effectiveness of sucralfate appeared unrelated to acid neutralization in keeping with its classification as a cytoprotective agent. There were eight antacid-related side effects (four severe diarrhea, four hypermagnesemia), and none related to sucralfate. Sucralfate suspension was safe and effective and had fewer side effects than antacid titration for the prophylaxis of stress-related bleeding in critically ill patients.

In a continuation of a trial for which preliminary results were reported in the Journal two years ago, a total of 64 patients with Child Class C cirrhosis and variceal hemorrhage requiring six or more units of blood were randomly assigned to receive either a portacaval shunt (32 patients) or endoscopic sclerotherapy (32 patients). The duration of initial hospitalization and the total amount of blood transfused during hospitalization were significantly less in the patients receiving sclerotherapy (P less than 0.001). There was no difference in short-term survival (50 percent of the sclerotherapy group were discharged alive, as compared with 44 percent of the shunt-surgery group). Both groups were followed for a mean of 530 days after randomization. Rebleeding from varices, the duration of rehospitalization for hemorrhage, and transfusions received after discharge were all significantly greater in the sclerotherapy group (P less than 0.001). Forty percent of the sclerotherapy-treated patients discharged alive (7 of 16 patients) ultimately required surgical treatment for bleeding varices, despite a mean of 6.1 treatment sessions. Health care costs and long-term survival did not differ significantly between the groups (P greater than 0.05). We conclude that although endoscopic sclerotherapy is as good as surgical shunting for the acute management of variceal hemorrhage in poor-risk patients with massive bleeding, sclerotherapy-treated patients in whom varices are not obliterated and bleeding continues should be considered for elective shunt surgery.

The effects on pancreatic growth and plasma CCK concentration of chronic feeding of camostate (400 mg/kg day for 10 days), a potent inhibitor of serine proteases including trypsin, were assessed in the mouse. For comparison, the trophic effects of chronic exogenous administration of CCK octapeptide (sc injection of 1 microgram/kg day every eight hours for 10 days) were also studied. In addition, the effects of a proglumide-analogue CCK-receptor antagonist (CR1409) on the stimulatory actions of camostate feeding and chronic administration of exogenous CCK were studied. The effects of the combination of chronic camostate feeding and sc injections of CCK, the effects of acute camostate feeding, and the effects of the CCK-receptor antagonist given without camostate or CCK were also studied. The results show that chronic camostate feeding markedly increased CCK plasma concentrations eight-fold over control values, and that acute camostate feeding increased plasma concentration to four fold of control values. Correspondingly, chronic camostate feeding markedly increased pancreatic weight, protein and DNA content. Exogenous CCK-8 also had qualitatively similar, but quantitatively less potent stimulatory effects. The combination of camostate and CCK-8 resulted in an additive stimulatory effect. The trophic actions of exogenous and endogenous CCK grossly increased chymotrypsinogen content, but left amylase content unaffected. The CCK-receptor antagonist CR 1409 completely abolished the trophic effects of exogenous CCK and greatly inhibited the effects of chronic camostate feeding. The CCK antagonist decreased pancreatic weight, DNA and protein content compared to control values when given without any CCK or camostate. We conclude that the protease inhibitor camostate is a very strong release effector of CCK and exerts a powerful trophic effect on mouse pancreas which is probably mediated by CCK. Furthermore, physiological increases of CCK during feeding of regular chow appear to exert trophic effects on the exocrine pancreas.

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.