M. Papp

Effect of a new potent CCK antagonist, lorglumide, on caerulein- and bombesin-induced pancreatic secretion and growth in the rat

1 The effect of lorglumide, a new potent cholecystokinin (CCK) antagonist, on pancreatic secretion and growth induced by caerulein and bombesin was studied in the rat. 2 Pancreatic exocrine secretion was studied both in vitro (isolated and perfused pancreatic segments) and in vivo (anaesthetized animals with cannulation of the common bile duct) whereas the trophic effect was investiged after short‐term (5 days) administration of the peptides and/or lorglumide. 3 Both caerulein and bombesin stimulated amylase release from in vitro pancreatic segments in a concentration‐dependent manner. Although the efficacy of both peptides was virtually identical, the potency of caerulein was higher than that of bombesin. Lorglumide displaced the concentration‐response curves to caerulein to the right without affecting the maximum response, suggesting a competitive antagonism. The Schild plot analysis of data gave a straight line with a slope not significantly different from unity. The calculated pA2 for lorglumide was 7.31 ± 0.45. The antagonist, however, was completely ineffective when tested against bombesin‐induced amylase release. 4 In vivo experiments confirmed results from in vitro studies since lorglumide (5 and 10 mg kg−1) significantly reduced pancreatic exocrine secretion induced by caerulein without affecting the response to bombesin. 5 Administration of either peptide increased the weight of the pancreas, the total pancreatic protein and DNA, trypsin and amylase content. Lorglumide (10 mg kg−1), administered together with caerulein, reduced the peptide‐induced increase in pancreatic weight, protein and enzyme content. On the contrary, when lorglumide was given together with bombesin, all the parameters that were examined were not altered by concomitant administration of the antagonist. 6 These results have demonstrated the ability of lorglumide to antagonize the effects on the pancreas of a CCK‐analogue, caerulein, and its inability to affect bombesin‐induced pancreatic secretion and growth, suggesting that lorglumide is a potent and selective antagonist of CCK‐receptors in the pancreas.

Bombesin promotes pancreatic growth in suckling rats

The pancreatic growth promoting effect of long term administration of bombesin was investigated in suckling rats. The authors showed that bombesin given in 10 μg/kg b.wt doses s.c. every 8 h for 10 days from the day of parturition stimulated pancreatic growth: it increased pancreatic weight, protein and DNA content, trypsin and amylase activity and trypsin/DNA ratio. Conclusion: Bombesin is an effective stimulator of pancreatic growth in suckling rats.

Effect of bombesin and its mammalian counterpart, GRP, on exocrine pancreas in the rat

The effect of equimolar doses (6 nmol/kg) of bombesin and its mammalian counterpart, GRP, on pancreatic growth and secretion was studied in adult rats. Both peptides were administered intraperitoneally three times a day for 5 consecutive days. Saline-treated rats were used as controls. At the end of the treatment, animals were anaesthetized and pancreatic juice was collected in basal conditions and after caerulein (0.75 nmol/kg i.p.) stimulation. Afterwards, the rats were sacrificed and growth and composition of the pancreatic tissue were determined. Compared with the control (saline) values, either basal or stimulated secretion was significantly increased after short-term treatment with both peptides. In addition, both bombesin and GRP increased pancreatic weight, total pancreatic protein, trypsin and amylase content. The DNA content was also increased by both peptides, although only the GRP effect proved to be significant. These results demonstrate that both bombesin and GRP have a growth-promoting effect on rat pancreas and concomitantly increase its secretory capacity. The mechanism of this peculiar biological action is likely to be connected with a direct stimulatory action on the gland.

Cholinergic and adrenergic control of enzyme secretion in isolated rat pancreas

While cholinergic nervous control of pancreatic enzyme secretion is well documented, data concerning adrenergic regulation of the exocrine pancreas are contradictory. In the present study we attempted to elucidate the direct action of adrenergic stimulation on pancreatic enzyme secretion. Rat pancreatic segments were set up in an organ bath and superfused with modified Krebs-Henseleit solution. Electrical field stimulation (EFS) stimulated amylase release from the segments. This stimulation was subject to inhibition with atropine up to 80%. Atropine-resistant enzyme discharge in response to EFS could be blocked by propranolol. Cholinergic agonist urecholine-induced amylase release was completely blocked by atropine. Noradrenaline (NA) exhibited a biphasic effect on amylase release. It inhibited the urecholine-induced amylase release in lower concentrations (10−8-10−7 M), while it stimulated basal enzyme secretion in higher concentrations (10−5-10−4 M). The inhibitory effect was mimicked by phenylephrine and completely prevented by prazosin. Isoprenaline concentration dependently enhanced, while clonidine and guanfacine did not affect amylase discharge. In conclusion, in rat pancreatic acinar tissue it seems likely that acetylcholine is the main neurotransmitter. Adrenergic action can be dual, inhibitory via α1-adrenoceptors or stimulatory via β-adrenoceptors on amylase secretion.

Inhibition of Pancreatic Secretory and Trophic Response to Caerulein by the H2-Receptor Antagonist Ranitidine in the Rat

The effect of ranitidine (20 mg . kg-1) and cimetidine (50 mg . kg-1) on pancreatic secretory and trophic responses to caerulein (1 microgram . kg-1) was studied in the rat. Ranitidine or cimetidine were administered alone or combined with caerulein twice a day for 7 days. Saline-treated rats were used as controls. At the end of treatment animals were anesthetized and pancreatic juice was collected for 1 h after intravenous secretin plus CCK-PZ (8 U . kg-1). Afterwards rats were sacrificed and growth and composition of pancreatic tissue were determined. Compared with control (saline) values, volume of pancreatic juice and output of trypsin and amylase were increased by treatment with caerulein. Ranitidine, when given combined with caerulein, completely abolished the secretory response induced by the peptide, whereas it was totally ineffective when given alone. Cimetidine (alone or combined with caerulein) was always ineffective. Caerulein increased pancreatic weight, total pancreatic trypsin, amylase and RNA content. Here again ranitidine, combined with caerulein, abolished almost completely the trophic effect of caerulein on the pancreas, but when given alone it did not influence pancreatic growth and composition. Also in this case, cimetidine was completely inactive. These results suggest that ranitidine affects exocrine pancreas with an action independent of the H2-receptor blockade.

Neuroeffector Transmission of the Hepatic and Pancreatico-Duodenal Isolated Arteries of the Dog

Direct evidence has been obtained that the neurogenic responses of the hepatic and pancreatico-duodenal arteries of the dog are mainly due to norepinephrine released from varicosities and that this effect is mediated via alpha 1-adrenoceptors. In addition, there is a prazosin-resistant response to nerve stimulation that is certainly not mediated via alpha 2-adrenoceptors. These vessels are 10-100 times less sensitive to applied norepinephrine than the great majority of peripheral arteries; however, the pA2 value for prazosin (7.5) is the same as in other systems. The varicose terminal plexus is located deep in the media, as shown by electron microscopic study. Findings indicate that these gastrointestinal arteries are mainly controlled by adrenergic innervation, that their density is as high as that of any other vessel, and that these arteries might be much less influenced by the circulating catecholamines than others. The neuroeffector transmission of hepatic and pancreatico-duodenal arteries is subject to presynaptic modulation. Muscarinic (oxotremorine) and P1 (adenosine) receptor agonists are effective inhibitors of transmission, whereas xylazine surprisingly has no effect.

ALCOHOL DOES NOT AFFECT THE TROPHIC PANCREATIC EFFECT OF CCK AND ITS PLASMA LEVEL IN YOUNG RATS

face the possible development of pancreatic cancer in the patient and in (asymptomatic?) members of his family. This is particularly relevant in those patients without biliary disease and without a history of alcohol abuse. administered for 3 months counteracted the trophic pancreatic effects of endogenous cholecystokinin (CCK) on partially resected adult rat pancreas (1). These authors had earlier reported that alcohol (5 g/kg/day) applied for 2 weeks eliminated pan-

Caerulein stimulates pancreatic growth and somatic growth in suckling rats

SummaryThis study deals with the stimulatory effect of caerulein on pancreatic and somatic growth in CFY suckling rats before weaning. After birth, caerulein (0.25, 0.5, 1, 3, 10 and 30 μg/kg) was given subcutaneously (s.c.) 3 times daily for 10 days. Salinetreated newborn rats were used as control. Caerulein increased pancreatic weight and total pancreatic trypsin activity reaching the maximum at 1 μg/kg dose; higher doses did not cause higher values. On this basis 1 μg/kg caerulein was applied s.c. 3 times daily for 3, 5, 10 and 20 days. At the end of the treatment pancreatic weight, total pancreatic protein, DNA content, trypsin and amylase activity was measured. Increases in body weight due to caerulein treatment were found from 6 days of treatment. Caerulein treatment increased pancreatic weight, total pancreatic DNA and protein content, and trypsin and amylase activity when applied for 5, 10 and 20 days. Treatment for 3, 5, 10 and 20 days with caerulein preferentially increased pancreatic trypsin activity compared to amylase activity. Trypsin activity per mg DNA increased with time in each caerulein-treated group demonstrating that the effect of caerulein increases with duration of treatment. In the saline-treated control group, however, pronounced increase in pancreatic amylase activity compared to that of trypsin activity was found in the age between days 11 and 21. This may be explained by the observation that the plasma corticosterone level increased during this period of postnatal life. The effect of caerulein in promoting pancreatic and somatic growth of suckling rats before weaning may be attributed to a specific enhancing effect of the peptide on proteolytic (e.g. trypsin) enzyme production of the pancreas.

Beneficial effects of preventive oral administration of camostate on cerulein-induced pancreatitis in rats.

To The Editor: We read with great interest the article of Otsuki et al on the beneficial effects of the synthetic trypsin inhibitor camostate (FOY 305) applied by gavage as a treatment in cerulein-induced acute pancreatitis in rats (t). Intravenous FOY or FOY 305 improved the course of sodium taurocholateor cerulein-induced pancreatitis (2-4). It is suggested that the favorable effects of camostate may be attributed to: (1) absorption of camostate and its metabolites from the intestines into the blood, (2) stimulation of release of endogenous secretion and CCK increasing pancreatic juice secretion, and (3) reducing intraacinar vacuolization ( 1 ). These vacuoles contain digestive enzymes and lysosomal hydrolases (4, 5), among them cathepsin B, which lysosomal enzyme activates trypsinogen to trypsin (6). A single dose of oral camostate almost abolished pancreatic digestive enzyme content in rats (7). Trypsin is suggested to be the trigger of acute pancreatitis (6). Starting from the data mentioned before, we studied how a single oral dose of camostate influences pancreatic trypsin content and onset of cerulein-induced pancreatitis (8) in rats. Pancreatitis was induced by four supramaximal subcutaneous doses of cerulein (20 txg/kg; Takus, Farmitalia) given at hourly intervals (1). Nonfasted 6-week-old Wistar rats were used. Camostate (400 mg,&g; Ono, Pharmaceutical Co., Osaka, Japan) was given by gavage once at 1 hr before the first cerulein injection. Five hours after the first cerulein injection, the rats were exsanguinated and their pancreata removed, weighed, and analyzed. Plasma amylase level, pancreatic trypsin, and protein content (methods in ref. 9) were determined, and specimens of the pancreata were examined by histology. One rat was used only once. Statistical analysis was performed by ANOVA and the Dunn and Dunnett contrast (9). Camostate alone caused pancreatic trypsin content almost disappear for 5 hr and decreased protein content (Table 1, part A). Cerulein increased pancreatic weight and trypsin and protein content due to blocked enzyme secretion and unchanged protein synthesis (5) and caused a fivehold increase in plasma amylase level vs control. In combination with cerulein, camostate reduced the increase in pancreatic weight by 20% and trypsin content by about 25% (Table 1, part B). The elevated plasma amylase level due to cerulein was not affected by camostate. Histology revealed cerulein-induced pancreatic edema and vacuolization of acinar cells. Coadministration of camostate reduced the extension of edema and vacuolization of acinar cells (data are not shown). In conclusion, oral camostate depleted pancreatic trypsin content. Due to this, preventive oral application of camostate had beneficial effects on ceruleininduced acute pancreatitis in rats.

Pancreatic secretory and trophic response to caerulein in rats: Effect of proglumide and lorglumide

Summary— The effect of proglumide and lorglumide, two CCK‐receptor antagonists, on caerulein‐induced pancreatic secretion and growth was studied in the rat. In anaesthetised animals, caerulein (1 μg/kg) significantly increased the volume of pancreatic juice and protein output. Lorglumide (5 and 10 mg/kg), administered intraperitoneally 15 min before stimulation, reduced peptide‐induced pancreatic exocrine secretion. By contrast, proglumide (100 and 400 mg/kg) was completely ineffective. In experiments dealing with the trophic effect of caerulein, both drugs were administered alone or combined with the peptide (1 μ/g/kg) 3 times daily for 5 d. Saline‐treated rats served as controls. At the end of the experiment, rats were sacrificed, and growth and composition of pancreatic tissue were determined. Pretreatment of the animals with either proglumide or lorglumide did not affect pancreatic size and composition. Caerulein increased the weight of the pancreas, the total pancreatic protein, trypsin, amylase, and DNA content. After pretreatment with proglumide, all these parameters were not significantly different from those obtained with caerulein alone. In contrast, when lorglumide was given together with caerulein, it significantly reduced caerulein‐induced pancreatic growth and decreased enzymatic protein content of the gland. These results show that lorglumide is a much more potent and effective CCK‐receptor antagonist than proglumide. Its ability to antagonize the pancreatic secretory and trophic action of a CCK‐analogue (i.e. caerulein) supports the view that these physiological actions of CCK are mediated through an interaction of the hormone with specific receptors.