The effect of CR 1409, a potent CCK receptor antagonist, on basal and stimulated pancreatic secretion in rat

Effect of cholecystokinin1 receptor antagonist loxiglumide (CR1505) on basal pancreatic exocrine secretion in conscious rats

INTRODUCTION AND AIM

To examine the involvement of cholecystokinin (CCK) in the basal pancreatic exocrine, we investigated the effect of loxiglumide (CR1505), a CCK1 receptor antagonist, on basal pancreatic exocrine secretion in conscious rats.

METHODOLOGY

After the basal collection of pancreatic juice for 1 hour, loxiglumide (10 mg/kg/h) or saline was infused via the femoral vein continuously for 2 hours.

RESULTS

Loxiglumide significantly suppressed the basal pancreatic protein and amylase outputs. However, loxiglumide did not alter the basal pancreatic juice volume.

CONCLUSIONS

These results demonstrate that loxiglumide suppresses basal pancreatic exocrine secretion in normal rats. They also suggest that CCK is involved in basal pancreatic exocrine in conscious rats and that loxiglumide may be useful as a therapeutic agent for pancreatitis, even during fasting, by attenuating the basal pancreatic exocrine burden on the pancreas.

Bovine pancreatic secretion in the first week of life: potential involvement of intestinal CCK receptors

The aim of this study was to evaluate pancreatic juice secretion of calves in the first postnatal days, and determine a potential involvement of cholecystokinin (CCK) and intestinal CCK receptor in its regulation. Nine neonatal Friesian calves (five controls and four treated intraduodenally with FK480, a CCK-A receptor antagonist) were surgically fitted with a pancreatic duct catheter and a duodenal cannula before the first colostrum feeding. Collections of pancreatic juice and duodenal luminal pressure recordings were started early after recovery from anaesthesia and continued for 6 days. From day 2 or 3 of life, periodic fluctuations in pancreatic secretions were observed in concert with duodenal myoelectric motor complex (MMC) and variations in plasma pancreatic polypeptide (PP) concentrations. Intraduodenal administration of FK480 reduced pancreatic juice secretion while intravenous infusion of CCK had no effect. Immunocytochemistry indicated an association of mucosal CCK-A and -B receptors with neural components of the small intestine. In conclusion, periodic activity of the exocrine pancreas exists in neonatal calves soon after birth and local neural intestinal CCK-A receptors could be partly responsible for the modulation of neonatal calf pancreatic secretion.

Effect of L364718 on interdigestive pancreatic exocrine secretion and gastroduodenal motility in conscious sheep

The present study examined roles of endogenous cholecystokinin (CCK) and CCK-A receptors in the regulation of pancreatic exocrine secretion and gastroduodenal motility in conscious sheep during interdigestive period. Interdigestive exocrine secretion of ovine pancreas changed cyclically corresponding with cycle of duodenal migrating myoelectric complexes (MMC). During second phase of the duodenal MMC, intravenous injection of L364,718 at 2.45 mumol kg-1 inhibited exogenous CCK-8-induced pancreatic exocrine secretion. Intravenous infusion of the antagonist at 2.45 mumol kg-1/5 min for 5 min also inhibited significantly the pancreatic enzyme secretion without CCK-stimulation to half of that in the control, but not the fluid and bicarbonate secretion. Atropine infusion (i.v.) at 72.0 nmol kg-1/5 min significantly inhibited not only enzyme but also fluid and bicarbonate secretion. Corresponding to the inhibition of the exocrine secretion, L364,718 induced premature phase III in duodenal electromyogram (EMG) in three of the five sheep. Omasal EMG was inhibited slightly but significantly by L364,718, however, neither regular ruminal contractions nor abomasal EMG were altered by L364,718. In contrast, the atropine infusion inhibited only amplitude of ruminal contractions. These results suggest that endogenous CCK contributes to the regulation of interdigestive pancreatic exocrine secretion, omasal contractions and duodenal MMC in the ovine gastrointestinal tract via CCK-A receptors.

Duration and potency of anticholecystokinin action of subcutaneous and oral loxiglumide on cerulein-stimulated pancreatic exocrine secretion

The duration and the potency of the antiCCK activities of loxiglumide given by sc and oral routes were examined in rats. Pancreatic juice flow and protein output in response to an iv bolus injection of cerulein (100 ng/kg body wt) were measured at specified time intervals from 1-12 h after loxiglumide administration. Subcutaneous loxiglumide (10 g/kg body wt) effectively suppressed cerulein-stimulated protein output for 4 h and pancreatic juice volume for 6 h, when total outputs during a 60-min period after cerulein stimulation were compared with the control value without loxiglumide pretreatment. Oral dose of loxiglumide exerted longer-term anti-CCK activity (protein output: 6 h, pancreatic juice: 8 h) than the same sc dose. In addition, oral loxiglumide showed more potent suppression of protein output than the same sc dose at the corresponding time interval. Higher oral dose of loxiglumide (50 mg/kg body wt) caused longer inhibition on both protein (8 h) and pancreatic juice secretion (12 h). These results suggest that the half-life of loxiglumide given by oral route is longer than that by sc route or that the bioavailability of oral loxiglumide is higher than that of sc dose. The present study demonstrates that loxiglumide, given either by sc or by oral route, has long duration of action in antagonizing responses to exogenously administered cerulein.

CCK and PYY do not participate in the delayed inhibition of pancreatic secretion, after stimulation by duodenal oleic acid infusion

The role played by CCK in the stimulation of pancreatic secretion by duodenal infusion of oleic acid in conscious rats was studied using a potent and specific CCK receptor antagonist. CR-1409 did not alter basal secretion, which does not require CCK. The three doses of CR-1409 that were used (2, 4 and 8 mg/kg/h) suppressed the protein response to duodenal infusion of oleic acid and significantly enhanced the delayed inhibition normally observed in control rats (-81%, -87% and -88% vs. -51% of basal in controls). CR-1409 dose-dependently reduced the volume of pancreatic secretion after duodenal infusion of oleic acid (0.40 +/- 0.02, 0.36 +/- 0.02, 0.34 +/- 0.03 vs. 0.48 +/- 0.04 ml/30 min for 2, 4, 8 mg/kg/h and controls, respectively) and revealed a delayed inhibition of volume and a slight reduction of bicarbonate secretion. CCK appears to be directly responsible for the protein and also water response to duodenal infusion of oleic acid, and to be indirectly involved in bicarbonate stimulation. PYY antiserum significantly augmented protein output after duodenal infusion of oleic acid (10.75 +/- 1.40, 14.10 +/- 1.60 vs. 8.60 +/- 1.20 mg/30 min, 1 microliter, 2 microliters and controls), but failed to modify the delayed inhibition: PYY modulates the response to duodenal infusion of oleic acid and is not involved in the delayed inhibition, which was shown to be also present for volume, but which is normally masked by the action of CCK.

Perspectives of CCK antagonists in pancreatic research. Part II. Experimental studies

In this article, the effects of different classes of cholecystokinin (CCK) receptor antagonists in CCK-related physiological processes of the pancreas have been discussed. Both glutaramic acid derivatives and natural (benzodiazepine) analogs are potent, competitive antagonists of peripheral CCK receptors. These compounds thus provide a powerful tool for investigating the physiological and pharmacological actions of CCK in the gastrointestinal system, and have already clarified the role of CCK in pancreatic secretion and trophism or growth.

Perspectives of CCK antagonists in pancreatic research and clinical use. Part I

Cholecystokinin (CCK) is one of the most important regulators of pancreatic and digestive physiology. Its importance led to research and discovery of a number of CCK receptor antagonists. Some of them are experimentally and clinically used today in order to assess the relative contribution of CCK to different aspects of pancreatic physiology. Furthermore, clinical trials are running with the aim of determining their possible therapeutic indications in pancreatic diseases, such as acute and chronic pancreatitis or pancreatic carcinoma. The rationale and evidence for their use are discussed.