James R. Wisner

Effects of L-364,718, a New Cholecystokinin Receptor Antagonist, on Camostate-Induced Growth of the Rat Pancreas

Chronic feeding of rats with camostate results in pancreatic hypertrophy or hyperplasia, or both. Previous studies suggest that this effect of camostate occurs via an increase in endogenous cholecystokinin due to an enteral feedback mechanism involving the inhibition of trypsin in the duodenum. Studies employing proglumide, a weak and relatively nonspecific cholecystokinin antagonist, have failed to fully abolish camostate-induced pancreas growth. We examined the effects of L-364,718, a new and highly potent cholecystokinin receptor antagonist, on camostate-induced pancreas growth in rats. The pancreas weights and the concentrations of ribonucleic acid, protein, and chymotrypsinogen in the pancreas of rats treated with camostate alone were significantly elevated over those of controls. These effects of camostate were completely abolished in rats treated with camostate + L-364,718. The pancreas weights and the concentrations of deoxyribonucleic acid and ribonucleic acid in the pancreas of rats treated with L-364,718 alone were significantly lower than values in control rats. These data indicate that camostate-induced pancreas growth in rats appears to be dependent on the actions of endogenous cholecystokinin and that cholecystokinin may play a role in the maintenance of pancreatic growth in normal rats.

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&OV0401;, 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 μg/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.

Pancreatic secretion after secretin and cholecystokinin stimulation in chronic alcoholics with and without cirrhosis

We have studied the volume, protein concentration, total protein, and chymotrypsin and trypsin outputs in pure pancreatic juice (PPJ) following endoscopic cannulation of the pancreatic duct in 11 male and 2 female patients with advanced alcoholic cirrhosis (AC). Results were compared to those obtained from 21 nonalcoholic volunteers (NAV) and 26 chronic alcoholic (CA) patients without cirrhosis. Intravenous stimulation with secretin followed 10 min later by intravenous cholecystokinin-pancreozymin (CCK-PZ) resulted in highly significant increases in volumes during both phases of pancreatic stimulation in AC compared to NAV and CA. Protein concentration and total output during secretin stimulation was not different among the three groups. During CCK-PZ stimulation, CA exhibited a significant elevation in protein concentration and total output compared to NAV and AC. Although total chymotrypsin output was lower in secretin-stimulated CA than other groups, no other differences between the groups were observed in either of the hormone-stimulation phases. Marked elevations in trypsin output were observed in secretin-stimulated AC and in CCK-PZ-stimulated AC and CA. The high PPJ volume and the relatively low protein concentration observed in AC may effect a washout phenomenon resulting in a decreased tendency for ductal protein precipitation in these patients.

Chronic alcohol consumption intensifies caerulein-induced acute pancreatitis in the rat.

SummaryRats were chronically fed either an ethanol-containing diet (36% of total calories derived from alcohol) or a pair-fed, control diet (no alcohol) for 8 wk, and acute pancreatitis (AP) was subsequently induced by a 3-h iv infusion of caerulein (CR) at a dose of 5 μg/kg/hr. CR-induced AP in control rats (no alcohol) was characterized by a significant elevation in serum lipase content, pancreatic interstitial edema, infrequent occurrences of karyorrhexis, and the appearance of vacuoles in acinar cells. Chronic feeding of the ethanol diet followed by treatment with CR resulted in increases in serum lipase content, interstitial edema, karyorrhexis, and acinar vacuolization that were significantly greater than that seen in rats fed the control diet and treated with CR. It is concluded that chronic ethanol intake in the rat intensifies AP that is subsequently induced by CR.

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

SummaryLarge 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.

Asperlicin, a nonpeptidal cholecystokinin receptor antagonist, attenuates sodium taurocholate-induced acute pancreatitis in rats.

Asperlicin (ASP), a new, nonpeptidal cholecystokinin (CCK) receptor antagonist isolated from the fungus Aspergillus alliacerrs, has an affinity that is 300–400 times greater than that of proglumide for gallbladder, ileal, and pancreatic CCK receptors. The long in vivo half-life and high selectivity for peripheral CCK receptors make ASP suitable for investigations on the physiological and pharmacological actions of CCK. Endogenous CCK has been postulated to participate in the pathogenesis of acute hemorrhagic pancreatitis (AHP) in rats and mice. We examined the effects of ASP in rats on the early course (6 h) of AHP induced by a retrograde infusion of sodium taurocholate (NaTC) into the common bile-pancreatic duct. An i.v. bolus injection of ASP (either 10 mg/kg or 30 mg/kg) in dimethyl sulfoxide (DMSO) given 1 h prior to AHP induction failed to significantly alter pancreas weights, serum amylase concentrations, or pancreatic histopathology when compared with AHP controlrats treated with vehicle alone. However, rats given 2 i.p. injections of ASP (either 20 mg/kg/injection or 40 mg/kg/injection) in DMSO:olive oil 1 h before and 2 h after induction of AHP exhibited significantly reduced serum amylase concentrations. Additionally, rats given the high dose i.p. injections of ASP also had significantly reduced pancreas weights and less severe pancreas histopathology compared with AHP control animals. These data indicate that endogenous CCK participates in the pathogenesis of NaTC-induced AHP in the rat.

Chronic administration of a potent cholecystokinin receptor antagonist, L-364,718, fails to inhibit pancreas growth in preweanling rats.

We examined whether endogenous cholecystokinin (CCK) is involved in growth of the preweanling rat pancreas. Twice daily for 14 days, 7-day-old neonatal rats received an oral gavage of either 2.5 mg/kg or 5.0 mg/kg of the potent and specific CCK receptor antagonist L-364,718 (the 2.5 mg/kg dose of antagonist was shown in the present study to abolish totally the pancreas growth-promoting effects of exogenously administered caerulein (CR) in neonatal rats). Control pups received oral gavages of the L-364,718 vehicle alone. The final body weights, pancreas weights, total pancreatic DNA contents, and total pancreatic protein contents did not differ significantly between the 21-day-old control pups and the 21-day-old pups that were pretreated for 14 days with either the low or the high doses of L-364,718. These findings suggest that endogenous CCK is not required for growth of the neonatal rat pancreas.

The effects of nafamostat mesilate (FUT-175) on caerulein-induced acute pancreatitis in the rat

SummaryWe examined the ability of a highly potent synthetic protease inhibitor, nafamostat mesilate (FUT-175), to protect the rat pancreas against AP induced by a supramaximal dose of caerulein (CR). Rats received a 6-h, continuous intravenous (iv) infusion of either CR alone or CR + a 6-h infusion of either 2.5, 5.0, 10.0, 25.0, or 50.0 mg of FUT-175/kg/h. Pancreas weights and serum chymotrypsinogen concentrations were significantly elevated by approximately 85 and 75%, respectively, over values in saline infused rats. Pancreas weights in rats treated with CR+ FUT-175 at doses from 2.5–25.0 mg/kg/h were significantly reduced by approximately 20% compared to rats given CR along, and histology showed a reduction in the extent and size of acinar cell vacuolization and reduced interstitial edema compared to rats treated with CR alone. Serum chymotrypsinogen concentrations in rats treated with CR and either 5.0 or 10.0 mg of FUT-175/kg/h were significantly lower than in rats given CR alone. Significant mortality occurred in rats infused with FUT-175 at doses of either 25.0 or 50.0 mg of FUT-175/kg/h. These data indicate that serine proteases appear to be involved in the pathogenesis of CR induced AP in rats and that FUT-175 administered in low doses (2.5–10.0 mg/kg/h) provides significant protection against this form of pancreatitis.

ACUTE ADMINISTRATION OF INTACT PARATHYROID HORMONE BUT NOT ITS AMINO-TERMINAL FRAGMENT STIMULATES VOLUME OF PANCREATIC SECRETION

Chronic renal failure is associated with structural and functional abnormalities of the exocrine system of the pancreas. Certain data suggest that the excess parathyroid hormone (PTH) in these patients may participate in the genesis of these pancreatic derangements. However, direct evidence that PTH exerts a direct effect on the exocrine pancreatic system is not well documented. The present study examined the effects of the intact molecule (1-84 PTH) and of the amino-terminal fragment (1-34 PTH) of the hormone on the basal output of pure pancreatic juice (PPJ) volume and pancreatic protein secretion in the rat. 1-84 PTH but not 1-34 PTH significantly (p less than 0.01) stimulated the output of PPJ volume without an effect on protein secretion. The magnitude of this stimulatory effect of 1-84 PTH depended on the dose of the hormone administered, and it was related to its biological activity, since inactivation of PTH abolished its action on the output of PPJ volume. The simultaneous administration of the calcium channel blocker, verapamil, reduced but did not abolish the stimulatory effect of PTH on the volume of PPJ output. The data demonstrate that: (1) the ductal cells of the pancreatic acini are targets for PTH and (2) the action of the hormone on these cells is mediated, at least in part, via PTH-induced entry of calcium into the target cells.

Evidence against cholecystokinin mediation of basal and bombesin-stimulated pancreatic secretion in the rat

Studies in dogs suggest that bombesin-stimulated pancreatic exocrine function is mediated via endogenous cholecystokinin. We studied (a) the short-term effects of bombesin on pancreatic juice volume and protein output in unconscious rats and (b) whether a potent cholecystokinin-receptor antagonist, L-364,718, affects the pancreatic exocrine response to bombesin. A 4-h i.v. infusion of low-dose (0.2 nmol/kg.h) or high-dose (1.0 nmol/kg.h) bombesin elicited significant increases in pancreatic juice volume and protein output, which were unaltered by treatment with L-364,718 at a dose capable of fully suppressing cholecystokinin-octapeptide-stimulated pancreatic juice volume and protein output. We conclude that the effects of exogenously administered bombesin on the exocrine pancreas in the rat are not mediated via release of endogenous cholecystokinin.