Cholecystokinin antagonist prevents hyperamylasemia and improves pancreatic exocrine function in cerulein-induced acute pancreatitis

Role of CCK/gastrin receptors in gastrointestinal/metabolic diseases and results of human studies using gastrin/CCK receptor agonists/antagonists in these diseases

In this paper, the established and possible roles of CCK1 and CCK2 receptors in gastrointestinal (GI) and metabolic diseases are reviewed and available results from human agonist/antagonist studies are discussed. While there is evidence for the involvement of CCK1R in numerous diseases including pancreatic disorders, motility disorders, tumor growth, regulation of satiety and a number of CCK-deficient states, the role of CCK1R in these conditions is not clearly defined. There are encouraging data from several clinical studies of CCK1R antagonists in some of these conditions, but their role as therapeutic agents remains unclear. The role of CCK2R in physiological (atrophic gastritis, pernicious anemia) and pathological (Zollinger-Ellison syndrome) hypergastrinemic states, its effects on the gastric mucosa (ECL cell hyperplasia, carcinoids, parietal cell mass) and its role in acid-peptic disorders are clearly defined. Furthermore, recent studies point to a possible role for CCK2R in a number of GI malignancies. Current data from human studies of CCK2R antagonists are presented and their potential role in the treatment of these conditions reviewed. Furthermore, the role of CCK2 receptors as targets for medical imaging is discussed.

Zymogen granule alterations in caerulein-induced pancreatitis developed during continuous hydrocortisone administration

BACKGROUND

The amount of enzymes stored in individual zymogen granules and the glycosylation of their membrane have been analysed in rats with acute pancreatitis induced by caerulein after hydrocortisone treatment. The consequences of prolonging hydrocortisone administration after pancreatitis and the use of the cholecystokinin (CCK) receptor antagonist, L-364,718, have also been evaluated.

MATERIALS AND METHODS

Analysis was performed using flow cytometry.

RESULTS

Caerulein-induced pancreatitis in rats previously treated for 7 days with hydrocortisone (10 mg kg-1 per day) revealed alterations in enzyme storage in the pancreas. Significant increases in amylase and trypsinogen contents in zymogen granules were observed, an effect associated with a reduction in L-fucose glycoconjugates. Pancreatitis persists 7 days later if hydrocortisone treatment is prolonged. At this stage, a reduced granule fucosylation was still observed, and a significant decrease in the amount of trypsinogen stored in the granules was found. However, hydrocortisone administration led to an increase in intragranular amylase quantities up to normal values, even when L-364,718 was simultaneously administered, but it reverted to plasma as a consequence of pancreatitis. The amount of N-acetyl D-glucosamine in the zymogen granule membrane was not altered by caerulein acute pancreatitis induced under continuous hydrocortisone treatment, but it was decreased by the administration of L-364,718 over 7 days after pancreatitis induction.

CONCLUSIONS

The administration of hydrocortisone after the development of pancreatitis prevented recurrence of the disease. L-364,718 proved to be detrimental, not only failing to reduce the symptoms of pancreatitis but also altering the glycoproteins of zymogen granule membrane.

The somatostatin receptor-adenylate cyclase system in rat pancreatic acinar membranes after temporary pancreaticobiliary duct ligation

The mechanism whereby somatostatin (SS) produces beneficial effects in established pancreatitis induced by pancreaticobiliary duct ligation (PBDL) is still not clear. The aim of the work was to evaluate the possibility of a direct action of SS on pancreatic acinar cells from rats with acute pancreatitis. For this purpose, we studied the SS-receptor-adenylate cyclase system in pancreatic acinar membranes from both, control rats and rats with experimentally induced acute pancreatitis. On the other hand, it has been reported that cholecystokinin (CCK) diminishes the number of SS receptors in pancreatic acinar cells. Proglumide, a CCK receptor antagonist reduces the severity of acute pancreatitis in the rat. Therefore, we have also examined the effect of proglumide on the somatostatinergic system in controls and rats with acute pancreatitis. Fourteen hours after PBDL, the SS receptors, the capacity of the SS analogue SMS 201-995 to inhibit forskolin-stimulated adenylate cyclase activity and PTX-catalyzed [32P] ADP-ribosylation of the alpha1 subunits of Gi proteins could not be detected in pancreatic acinar membranes. One month after reopening the closed pancreaticobiliary duct (PBD), the pancreas showed regeneration of acinar cells, and the above-mentioned parameters were significantly lower than in the control group. Two months after reopening the closed PBD, all these parameters had returned to control values. The administration of proglumide (20 mg/kg i.p.), a cholecystokinin receptor antagonist, accelerated pancreatic regeneration and approached all these parameters to control values one month after reopening the closed PBD. The present study suggests that the beneficial effects of SS on established pancreatitis induced by PBDL may not be due to a direct action of the peptide on pancreatic acinar cells at least at 14 hours after PBDL. In addition, these findings suggest that in established pancreatitis the effect of proglumide on the SS receptor-adenylate cyclase system could be due to its action on pancreatic regeneration.

Cathepsin B inhibition in two models of acute pancreatitis

The possible role of cathepsin B in the pathogenesis of two forms of acute pancreatitis was studied using the cathepsin B inhibitor known as E-64. In an edematous, nonfatal pancreatitis induced by supramaximal doses of cerulein, increases in the serum amylase and lipase levels were less pronounced in rats pretreated with E-64. Other parameters of pancreatic injury were unaffected by inhibition of cathepsin B. In a necrohemorrhagic type of pancreatic injury induced by retrograde infusion of bile salts into the pancreatic duct, E-64 partially attenuated increases in serum levels of amylase and lipase, and in addition, reduced the activation of trypsinogen. However, the high mortality in this model of pancreatitis was not modified.

Peptide YY ameliorates cerulein-induced pancreatic injury in the rat

Peptide YY (PYY), a known inhibitor of both pancreatic secretion and the release of cholecystokinin (CCK), may play a role in the pathophysiology of acute pancreatitis (AP). Supramaximal stimulation of the pancreas with CCK, or its analogue cerulein, induces edematous AP. We previously documented significant decreases in plasma PYY in sodium taurocholate-induced AP in the anesthetized pig, with exogenous PYY suppressing plasma amylase activity. We hypothesized that PYY may ameliorate cerulein-induced pancreatic injury in a conscious animal model. Thirty-two male Sprague-Dawley rats underwent chronic cannulation of the jugular vein and carotid artery for drug infusion and blood sampling. The animals were allowed to recover from anesthesia for a minimum of 16 hours, after which they were randomized to one of four (n = 8) treatment groups (cerulein 10 micrograms/kg/h, PYY 400 pmol/kg/h, cerulein+PYY, and control-saline 2 mL/kg/h). All treatments were administered by intravenous infusion over the first 6 hours of the experiment. Blood samples were taken prior to infusion and at 1, 3, 6, 9, and 24 hours into the study; the rats were then killed and the pancreata removed for weighing and histologic examination. All pancreatic specimens were graded in a blinded fashion for vacuolization, edema, inflammation, and necrosis. The mean basal plasma amylase level for all animals was 1,171 +/- 100 U/L and was not significantly different between groups. Infusion of cerulein resulted in significant increases in plasma amylase levels at 3, 6, 9, and 24 hours (4,827 +/- 1,022 U/L at 24 hours). In the group receiving both cerulein and PYY, the hyperamylasemia was attenuated with a return to basal values at 24 hours (1,206 +/- 103 U/L). There was significant pancreatic weight gain (1.99 +/- 0.07 g versus 1.03 +/- 0.07 g) and a worsened histologic picture in cerulein-treated animals compared with control animals (worsened edema, necrosis, and vacuolization). The addition of PYY to cerulein resulted in significantly lower pancreatic weight (1.27 +/- 0.11 g) than in the non-PYY-treated rats receiving cerulein. Pancreatic weight was not significantly different in this group compared with the control group. In addition, pancreatic histologic findings were significantly improved in those rats receiving PYY (decreased vacuolization and necrosis). Amylase levels, pancreatic weight, and morphologic findings were not significantly changed compared with basal values in the control or PYY alone treated groups. e conclude that as an inhibitor of pancreatic exocrine secretion, PYY ameliorates cerulein-induced pancreatic injury in the conscious rat.