Jun kinases are rapidly activated by cholecystokinin in rat pancreas both in vitro and in vivo

Stimulation of pancreatic acini from male Sprague-Dawley rats by both cholecystokinin (CCK)-8 and anisomycin caused an increase in p46jnk and p55jnk activities. Both forms of c-Jun amino-terminal kinase (JNK) were slightly activated at 5 min, reached a maximum at 30 min, and remained significantly increased at 60 min of CCK stimulation. By contrast, p42mapkwas activated fully by 5 min. In pancreatic acini stimulated with different concentrations of CCK for 30 min, the minimal and maximal JNK responses were observed at 30 pm and 100 nM CCK, respectively; p42mapk activation was, as previously reported, much more sensitive, with maximal activation by 1 nm CCK. Carbachol and bombesin also stimulated JNK activity, while vasoactive intestinal peptide did not. Neither activating protein kinase C nor increasing intracellular Ca2+ significantly activated JNK. In in vivo experiments, rats were infused intravenously for 5 and 15 min with a secretory (0.1 microg/kg/h) or supramaximal (10 microg/kg/h) dose of the CCK analog caerulein (CER). Secretory doses of CER induced a 4-fold increase of both forms of JNK in pancreatic tissue at 5 and 15 min, while at the same time points, supramaximal stimulation with CER caused 4- and 27-fold increases, respectively, of these kinase activities. The secretory dose of CER slightly increased the activities of both forms of mitogen-activated protein kinase, while the supramaximal dose induced a 10-fold increase of p42mapk at 5 min. In conclusion, JNKs and mitogen-activated protein kinases are rapidly activated in rat pancreatic acini stimulated with CCK as well as in pancreatic tissue during in vivo stimulation with CER. The large response to supramaximal CER stimulation may be of importance in the early pathogenesis of acute pancreatitis.     

Inhibitory effect of somatostatin analogue, SMS 201-995, on secretin-stimulated exocrine secretion in isolated perfused rat pancreas

In order to clarify the effect of somatostatin of the ductal secretion of the exocrine pancreas, we measured pancreatic juice and protein secretion stimulated with 10 pM secretin and/or 10 pM cholecystokinin (CCK) in the presence or absence of somatostatin analogue, SMS 201-995 (SMS) utilizing the isolated perfused pancreas of rats. SMS significantly inhibited both pancreatic juice flow and protein output elicited by 10 pM secretin without affecting basal secretion. The inhibitory effect of SMS was dose-dependent and maximal inhibition was observed with 1-10 nM. Half-inhibitory dose of SMS for juice secretion was 140 pM. Because CCK is thought to potentiate secretin action on the ductal system, we examined the effect of SMS on pancreatic secretory response to 10 pM secretin in combination with 10 pM CCK. In the experimental system we used, the amounts of pancreatic juice and protein secreted during a 30-min stimulation with secretin and CCK were additive. SMS inhibited both pancreatic juice and protein secretion to the level comparable with that obtained with either stimulus and SMS. SMS had no effect on CCK-stimulated pancreatic juice secretion but significantly inhibited protein output. The present study demonstrated, therefore, that SMS inhibits ductal secretion in response to physiological concentration of secretin.     

Comparison of the kinetics of pancreatic secretion and gut regulatory peptides in the plasma of preruminant calves fed milk or soybean protein

Exocrine secretion from the pancreas and concentrations of cholecystokinin, gastrin, secretin, and somatostatin in plasma were measured in relation to feeding in 70- to 120-d-old preruminant calves fed either a milk diet or a soybean diet. Pancreatic fluid was continuously collected, measured, and reintroduced in catheterized calves. Blood samples were withdrawn for measurements of gut regulatory peptide concentrations in plasma. A slight increase in outflow of pancreatic fluid was observed 30 min before the milk diet was introduced but not before the soybean diet was fed. In contrast, concentrations and outflows of protein and trypsin immediately after feeding were higher when calves were fed the soybean diet. Overall, during the first 5 h postfeeding, the outflow of pancreatic fluid was 40% higher when the milk diet was fed than when the soybean diet was fed. No difference in outflow of protein was observed, but that of trypsin was 82% higher when the soybean diet was fed. This enhanced enzyme secretion could have been related to the increased plasma concentrations of gastrin and cholecystokinin after the soybean diet was fed. Secretin release was less in calves fed the milk diet that in calves fed the soybean diet during the first 2 h postfeeding, suggesting that this gut peptide along with gastrin and cholecystokinin, contributed to the stimulation of enzyme secretion. Plasma gut regulatory peptides could be influenced by the soybean diet, which does not coagulate in the stomach, inducing faster gastric emptying of protein and fat, and by the chemical form of protein from the soybean diet and the lower susceptibility of these proteins to protease compared with casein. However, the resulting enhancement of pancreatic trypsin secretion and activity seemed to be insufficient to increase the digestibility of soybean protein up to a level similar to that of milk.     

Role of secretin in negative feedback regulation of postprandial pancreatic secretion in dogs

BACKGROUND: A negative feedback regulation of pancreatic exocrine secretion has been observed in fasting rats, pigs, and humans, but this phenomenon could not be found in fasting dogs. The aims of the present study were to investigate whether or not postprandial pancreatic secretion is regulated by a negative feedback mechanism and to determine if the mechanism is mediated by secretion and/or cholecystokinin (CCK) in dogs. METHODS: In eight dogs prepared with gastric and Herrera's pancreatic cannulas, pancreatic juice was collected for 3 hours after feeding a mixed meal to measure volume, bicarbonate, and trypsin output. Peripheral venous blood was obtained to determine plasma immunoreactive secretin and CCK levels. Four groups of experiments were performed while pancreatic juice was diverted from the duodenum: (1) diversion of pancreatic juice alone, (2) intraduodenal infusion of fresh pancreatic juice while pancreatic juice was diverted, (3) intraduodenal infusion of 150 mg/h of trypsin and 300 mg/h of chymotrypsin, and (4) intraduodenal infusion of 0.1 mol/L NaHCO3. RESULTS: Pancreatic secretion during diversion of pancreatic juice was significantly greater than that obtained while pancreatic juice was returned. Diversion-induced pancreatic hypersecretion was significantly suppressed by intraduodenal administration of pancreatic proteases, but it was not influenced significantly by 0.1 mol/L NaHCO3. The suppression by either pancreatic juice or proteases paralleled the decrease in plasma secretin response, whereas the CCK response remained unchanged. The inhibitory effect of pancreatic proteases on pancreatic secretion was blocked by a physiological dose of exogenous secretin, 0.06 clinical U.kg-1.h-1. CONCLUSIONS: In dogs, postprandial pancreatic secretion is controlled by a negative feedback mechanism mediated mainly by the release of secretin, but not by CCK.     

Effect of a new CCK-A receptor antagonist, dexloxiglumide, on the exocrine pancreas in the rat

The effect of dexloxiglumide, a new potent cholecystokinin (CCK) antagonist, on pancreatic enzyme secretion and growth was studied in the rat. 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 investigated after short-term (7 days) administration of the CCK-agonist, caerulein, or camostate (a potent trypsin inhibitor), with or without dexloxiglumide. CCK-8 stimulated amylase release from in vitro pancreatic segments in a concentration-dependent manner. Dexloxiglumide displaced the concentration response curves to CCK-8 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 (0.90 +/- 0.36) not significantly different from unity. The calculated pA2 for dexloxiglumide was 6.41 +/- 0.38. In vivo experiments confirmed results from in vitro studies since intravenous dexloxiglumide reduced pancreatic exocrine secretion induced by submaximal CCK-8 stimulation (0.5 nmol/kg/h) in a dose-dependent manner, the ID50 being 0.64 mg/kg. Both exogenous and endogenous (released by camostate) CCK increased the weight of the pancreas, the total pancreatic protein and DNA, trypsin and amylase content. Dexloxiglumide (25 mg/kg), administered together with caerulein (1 microgram/kg), reduced the peptide-induced increase in pancreatic weight, protein and enzyme content. Similarly, when dexloxiglumide was given together with camostate (200 mg/kg), all the observed changes were reduced by concomitant administration of the antagonist. These results demonstrate the ability of dexloxiglumide to antagonize the effects of CCK on pancreatic secretion and growth, suggesting that this compound is a potent and selective antagonist of CCK-A-receptors in the pancreas.     

Diazepam binding inhibitor is a potent cholecystokinin-releasing peptide in the intestine

Pancreatic proteases in the duodenum inhibit the release of cholecystokinin (CCK) and thus exert feedback control of pancreatic exocrine secretion. Exclusion of proteases from the duodenum either by the diversion of bile-pancreatic juice or by the addition of protease inhibitors stimulates exocrine pancreatic secretion. The mechanism by which pancreatic proteases in the duodenum regulate CCK secretion is unknown. In this study, we isolated a trypsin-sensitive peptide that is secreted intraduodenally, releases CCK, and stimulates pancreatic enzyme secretion in rats. This peptide was found to be identical to the porcine diazepam binding inhibitor by peptide sequencing and mass spectrometry analysis. Intraduodenal infusion of 200 ng of synthetic porcine diazepam binding inhibitor1-86 in rats significantly stimulated pancreatic amylase output. Infusion of the CCK antagonist MK-329 completely blocked the diazepam binding inhibitor-stimulated amylase secretion. Similarly, diazepam binding inhibitor33-52 [corrected] also stimulated CCK release and pancreatic secretion in a dose-dependent manner although it was 100 times less potent than the whole peptide. Using a perfusion system containing isolated mucosal cells from the proximal intestine of rats, porcine diazepam binding inhibitor 10(-12) M) dose dependently stimulated CCK secretion. In separate studies, it was demonstrated that luminal secretion of the diazepam binding inhibitor immunoreactivity (7.5 X 10(11) M) could be detected in rat's intestinal washing following the diversion of bile-pancreatic juice. The secretion of this peptide was inhibited by atropine. In conclusion, we have isolated and characterized a CCK-releasing peptide that has a sequence identical to the porcine diazepam binding inhibitor from pig intestinal mucosa and that stimulates CCK release when administered intraduodenally in rat. This peptide may mediate feedback regulation of pancreatic enzyme secretion.     

Building a relationship: communications and relationships between staff and stroke patients on a rehabilitation ward

Pancreatic enzyme storage and secretion were studied in rats treated twice daily with s.c. injections (5 micrograms/kg) of CCK-8 for 3, 7, and 15 days. Isolated zymogen granules were analyzed by flow cytometry to determine their FSC (forward scatter), SSC (side scatter), and amylase and trypsinogen contents. DNA content, pancreatic weight, and both basal and stimulated pancreatic secretion under i.v. CCK infusion (1.25 micrograms/kg/h) were also studies. Two subsets of zymogen granules were identified by flow cytometry in both control and CCK-treated rats on the basis of FSC and SSC parameters: Z1 (smaller and less complex) and Z2. Both subsets displayed a high degree of heterogeneity with respect to their enzyme content per zymogen granule. During the first 7 days of CCK treatment, hyperplasia and hypertrophy developed in the rats together with changes in the zymogen granules, reflected by a significantly decreased FSC, and increased SSC, and an increase in the mean trypsinogen/amylase ratio per granule. A rise in pancreatic enzyme secretion, especially of trypsin, was observed. After 15 days of CCK administration, a simultaneous decrease in amylase content and increase in trypsinogen content per zymogen granule was observed. A desensitization of the pancreas to CCK happened after 15 days of CCK administration, reflected by a reduction of all the pancreatic functions that had been increased at shorter CCK administration periods. Nevertheless, trypsinogen appeared resistant to desensitization because its secretion significantly increased in response to an i.v. infusion of CCK. CCK treatment displayed a differential packaging of the enzymes in individual zymogen granules; the trypsinogen/amylase ration was significantly higher in Z2 zymogen granules than in Z1 subset throughout the treatment.     

Absorption of zinc from lupin (Lupinus angustifolius)-based foods

The absorption of Zn from a lupin (Lupinus angustifolius) milk fortified with Ca, a bread containing lupin flour (230 g/kg), a sauce containing lupin flour and a sauce containing a lupin-protein isolate was determined in humans by measuring the whole-body retention of radioisotope from meals labelled with 0.02 MBq 65Zn, allowing for endogenous excretion of Zn, after 14 d. The absorption of Zn from the Ca-enriched milk (16.2%) and the bread made with lupin flour (27.0%) was similar to literature figures for comparable soya-bean products. The absorption from composite meals made with lupin flour (28.2%) and protein isolate (32.7%) was significantly higher than that reported for comparable soya-bean products. In a second experiment the absorption of Zn from a lupin-milk base and a soya-bean-milk base was compared with that from Ca-supplemented bases. The absorption of Zn from the lupin-milk base (26.3%) was significantly higher than from the soya-bean-milk base (17.6%), and neither was significantly altered by the addition of Ca. Overall the absorption of Zn from lupin-protein foods was found to be higher than from comparable soya-bean products. Lupin milk could be an attractive alternative to soya-bean milk for infant formulas.     

Behavior of exocrine pancreatic function during treatment with antibiotics and antineoplastic agents

The thesis is composed of two parts, the first part is concerned with experiments in rats, the second part confirms the findings in human beings. After administration of oxytetracycline, chloramphenicol and cyclophosphamide, respectively, to rats an approximately dose-dependent decrease in the pancreatic secretion of proteins and enzyme activities was demonstrable in vivo under exogenous stimulation. The exocrine pancreatic function was studied in humans by performing a secretin-pancreocymin test before and after treatment with oxytetracycline or chloramphenicol and before and after massive-dose therapy with cyclophosphamide or combined cytotoxic treatment (as outlined by De Vita). The investigations further included an examination of the exocrine pancreatic function in subjects on maintenance therapy with cyclophosphamide or busulfan and a comparison with the exocrine pancreatic function in a group of controls. In the oxytetracycline-treated humans there was a depression of the amylase and lipase activities in the duodenal secretion. Administration of chloramphenicol produced a decrease in the amylase output only. In the patients on massive-dose or continued therapy with cyclophosphamide the pancreatic function remained essentially unchanged. In contrast, cytotoxic combination treatment resulted in decreased activities of amylase and lipase. After maintenance treatment with busulfan a reduction of the trypsin and amylase activities was detectable. The volume and electrolyte outputs were found to remain essentially unchanged in all investigations. An impairment in enzyme synthesis is suggested as the major cause of the observed changes of pancreatic secretion after antibiotic and cytotoxic treatment.     

Cholestatic liver diseases in adults

BACKGROUND: Nitric oxide (NO) blockade by L-nitroarginine methyl ester (L-NAME) inhibits pancreatic secretion in vivo and aggravates caerulein induced pancreatitis. Nitric oxide synthase (NOS) is present in pancreatic islets, endothelium, and nerve fibres. L-NAME blocks all known NOS isoforms. AIM: To investigate the source of NO blocked by L-NAME that inhibits amylase secretion. METHODS: Amylase output was measured in rats in response to caerulein (0.1-50 microg/kg) alone or with indazole. Baseline secretion and the response to supramaximal caerulein were also examined after administration of indazole, L-NAME, haemoglobin, or aminoguanidine under continuous blood pressure measurement. In separate experiments, pancreatic secretion was measured after blockade of afferent nerve fibres by either systemic or local capsaicin. The effect of neural NOS inhibition on caerulein induced pancreatitis was also investigated. RESULTS: L-NAME, haemoglobin, and supramaximal caerulein (10 microg/kg) increased blood pressure, whereas indazole and suboptimal caerulein (0.1 microg/kg) did not. Indazole and capsaicin decreased basal amylase output. L-NAME and haemoglobin reduced basal amylase output to a lesser extent and potentiated the inhibitory response to supramaximal caerulein. In contrast, full neural NOS inhibition by L-NAME partially reversed the expected caerulein induced suppression of amylase output. This effect was reproduced by indazole and capsaicin. Indazole did not alter responses to either optimal (0.25 microg/kg) or suboptimal (0.1 microg/kg) caerulein, nor, in contrast with L-NAME, aggravate the outcome of caerulein induced pancreatitis. CONCLUSIONS: Reduction of circulating NO availability, probably of endothelial origin, is responsible for the decrease in amylase secretion observed in the early response to L-NAME. Nitrergic neurotransmission plays an important role in the control of pancreatic secretion and may induce opposite effects to endothelial NOS activity.     

Modification of unit responses to gustatory stimuli by conditioned taste aversion in rats

Secretion of trypsin, chymotrypsin, lipase and amylase was measured in male rats under urethane anaesthesia using a method of continuous perfusion of the duodenum. Prolonged infusion of cholecystokinin-pancreozymin (CCK-PZ) over a period lasting 200-360 min was administered either alone or together with a submaximal dose of secretin (1 unit/100 g - 10 min). Infusion of CCK-PZ was carried out using maximal doses (1--1.5 unit/100 g - 10 min) with and without secretin. Supramaximal doses of CCK-PZ (2 and 4 units/100 g - 10 min) were used only in combination with secretin. In all experiments secretion of enzymes showed a triphasic pattern including an initial peak followed by a plateau secretion after 10--20 min (phase 1), a decreasing second phase and finally base-line secretion (phase 3), thus demonstrating exhaustion of enzyme output from the gland with time. With increasing and supramaximal dose of CCK-PZ the cumulative output of enzymes from start to baseline secretion decreased progressively. Under the same conditions the levels of peak and plateau secretion were lower, the duration of plateau secretion was longer and the decreasing phase of secretion was shortened. These features indicate inhibition of secretion with increasing supramaximal doses of CCK-PZ infusion. Whereas the proteolytic enzymes and lipase reacted in a parallel way always amylase secretion was sustained on a higher level, implicating an alternative pathway for secretion.     

Blepharophimosis: a causally heterogeneous malformation frequently associated with developmental disabilities

The effects of loxiglumide (CAS 107097-80-3, CR 1505), a novel cholecystokinin-A(CCK-A) receptor antagonist, on pancreatic exocrine secretion stimulated by exogenously administered CCK-8 were examined in conscious dogs with chronic pancreatic fistula. Pancreatic exocrine secretion in dogs was significantly increased by intravenous infusion of CCK-8 at a dose of 0.06 microgram/kg/h. Loxiglumide inhibited CCK-8-augmented outputs of pancreatic protein, trypsin and amylase at intravenous doses of 1, 3, 10 mg/kg/h (p < 0.05 or 0.01), and inhibited pancreatic juice volume at a dose of 10 mg/kg/h (p < 0.05). These results demonstrated that the selective CCK-A antagonist loxiglumide inhibited the increase of pancreatic exocrine secretion stimulated by CCK-8 based on selective blockade of receptor binding of CCK in dogs.     

Exocrine pancreatic secretion in man following one week of M1-muscarinic receptor blockade

A double-blind, randomized, placebo-controlled crossover study was performed to assess the influence of one week of selective M1-muscarinic receptor blockade on pancreatic exocrine secretion in man. Ten healthy subjects received telenzepine (3 mg p.o.) and placebo each for 8 days, with a 6-day drug-free washout interval between treatment sequences. On Day 8 of each sequence, pancreatic secretion was stimulated for 2 h by infusion of submaximal secretin (0.2 U.kg/h) followed by maximal stimulation with secretin (1.0 U.kg/h) and ceruletide (120 ng.kg/h). Telenzepine had no significant effect on secretory parameters during submaximal stimulation with secretin. During maximal stimulation, total protein, secretory volume, and output of amylase, trypsin and bicarbonate were unexpectedly increased by telenzepine. These findings might be partially explained by removal of the inhibitory influence of pancreatic polypeptide, which was depressed by telenzepine. Acute studies have shown that M1-receptor antagonists inhibit exocrine secretion. Our results suggest that adaptation of physiological mechanisms governing the exocrine pancreas may occur after one week of receptor blockade by a therapeutic dosage of telenzepine, to the extent that M1-blockade no longer inhibits secretion.     

Cholecystokinin is not a physiological regulator of gastric pepsin secretion in rats

The physiological relevance of cholecystokinin (CCK) in gastric pepsin secretion is unclear, although CCK has been reported to stimulate pepsin secretion in intact animals and in dispersed chief cell. To clarify the physiological role played by this peptide in pepsin secretion, we determined the effects of intravenous infusions of CCK on gastric pepsin release, and investigated the effect of endogenous CCK released by small amounts of trypsin inhibitor on pepsin secretion in conscious rats. The infusion of CCK-8 at 1 nmol/kg per h resulted in a plasma CCK concentration of 204 pM and a 2.5-fold increase in pepsin secretion compared to the baseline rate. The infusion of CCK-8 at 0.3 nmol/kg per h resulted in a plasma CCK concentration of 41.8 pM and also caused a significant increase in pepsin secretion compared to the baseline rate. However, the infusion of CCK-8 at 0.1 nmol/kg per h (plasma CCK level, 19.9 pM), which is still far beyond the physiological plasma levels of CCK, did not significantly affect pepsin secretion. In addition, the intraduodenal infusion of soybean trypsin inhibitor increased the plasma CCK concentration to 4.4 pM, a value comparable to that observed after feeding (3.3 pM), but again, this had no effect on gastric pepsin secretion. We conclude that CCK is not a physiological regulator of gastric pepsin secretion in rats.     

Regulation of the action of the novel cholecystokinin-releasing peptide diazepam binding inhibitor by inhibitory hormones and taurocholate

Diazepam binding inhibitor (DBI1-86) has recently been isolated in search for a cholecystokinin (CCK)-releasing peptide in the duodenum that is responsible for the feedback regulation of exocrine pancreatic secretion. Synthetic porcine DBI1-86 stimulates CCK release in vivo and in vitro from isolated intestinal mucosal cells. We postulated that DBI intraduodenally releases CCK in a paracrine fashion and might be the missing link in the feedback regulation of exocrine pancreatic secretion. Somatostatin, peptide YY (PYY) and taurocholate are known to inhibit feedback-stimulated CCK release in the rat. In this study, we investigated the effect of somatostatin, PYY and taurocholate on DBI-stimulated CCK secretion. Dispersed rat intestinal mucosal cells were prepared from the proximal small bowel and continuously perfused. The perfusate was collected and the release of CCK into the medium was measured. DBI1-86 dose-dependently stimulated CCK release, with a maximal effect at 10(-9) M. Somatostatin blocked the DBI-stimulated CCK release. Pretreatment of the cells with pertussis toxin fully reversed the inhibitory effect of somatostatin on DBI-stimulated CCK secretion, suggesting that somatostatin exerts its action by an inhibitory G-protein. In contrast, PYY (10(-6) M) and taurocholate (10(-6) M) did not affect DBI stimulated CCK levels, indicating that they act through different mechanisms to inhibit feedback-stimulated CCK release.     

Kinetics of pancreatic juice secretion in relation to duodenal migrating myoelectric complex in preruminant and ruminant calves fed twice daily

Daily secretion of pancreatic juice, including postprandial responses to food, was investigated in two groups of calves: preruminant (fed with liquid food) and ruminant (fed with solid food). Male Friesian calves (1 week old and 6 weeks old) were surgically fitted with a pancreatic duct catheter, duodenal cannula and two duodenal electrodes. Continuous 24 h collections of pancreatic juice and myoelectrical recordings were performed with minimal restraint and disturbance of animals. In both groups of calves clear periodic fluctuations in pancreatic juice secretion (volume, protein output and trypsin activity) coinciding with duodenal migrating myoelectric complexes (MMC) were recorded. Secretion of juice per cycle and per day was greater in ruminant calves, but the frequency and amplitude of cycles were lower in this group. There were no differences between day and night-time preprandial pancreatic cycles and duodenal MMC in preruminant calves, whilst in ruminant calves, evening MMC were longer than morning MMC. The pancreatic cephalic phase (increase of volume flow, protein output and trypsin activity during and just after food intake) was significant only in preruminant calves following morning feeding. Postprandial pancreatic cycles did not differ from preprandial cycles, except the pancreatic cycle (juice volume and trypsin activity) in which food was offered in preruminant calves. No gastric or intestinal phase was observed in either group of calves. In conclusion, biological cycles of the gastrointestinal tract are present in both preruminant and ruminant calves, and these cycles evolve along with the change from liquid to solid food.     

The influence of intravenous infusions of glucose and amino acids of pancreatic enzyme and mucosal protein synthesis in human subjects

BACKGROUND: Animal studies have shown that the synthesis and secretion of pancreatic enzymes and the turnover of mucosal proteins is strongly influenced by diet. METHODS: To determine whether the absorbed products of digestion are responsible for these changes, we investigated in groups of five healthy volunteers, the effects of i.v. infusions of amino acids (0.08 g/kg/h) and glucose (0.3 g/kg/h) on pancreatic enzyme and mucosal protein synthesis. Proteins were labeled in vivo by a 4-hours i.v. infusion of 14C-leucine and the enteric infusion of 3H-leucine tracer, during simultaneous cholecystokinin stimulation and duodenal collection of secreted pancreatic enzymes. Labeling of mucosal proteins was measured by endoscopic biopsy. RESULTS: The amino acid infusions elevated plasma amino acid levels, and the glucose infusions increased both glucose and insulin concentrations. The rates for amylase and trypsin secretion were significantly lower during the first 2 hours of glucose infusion and the rate of synthesis of trypsin was delayed by i.v. amino acid infusions from 52.1 +/- 4.1 to 77.6 +/- 8.5 minutes. Mucosal protein turnover rates were unaffected. 3H-labeling via the enteral route showed similar enzyme synthesis rates but variable mucosal incorporation rates. CONCLUSIONS: I.v. nutrients do not appear to stimulate the synthesis of pancreatic and mucosal proteins in human subjects.     

Chromium(VI) treatment of normal human lung cells results in guanine-specific DNA polymerase arrest, DNA-DNA cross-links and S-phase blockade of cell cycle

The effects of pancreatic secretagogues on the membrane fluidity of pancreatic acini were investigated using 1-[4-(trimethylammonium)phenyl]-6-phenyl-1,3,5-hexatriene iodide as a probe. Two kinds of pancreatic secretagogues, one category of which induces acute pancreatitis (cholecystokinin and carbachol) and another which does not induce acute pancreatitis (bombesin, CCK-JMV-180, and secretin), as well as lecithin were used to investigate the effect of changes in membrane fluidity of acini. Our study revealed that the membrane fluidity of the pancreatic acini was unaffected by a physiological dose (10(-11) M) of cholecystokinin. However, stimulation with a supramaximal dose of cholecystokinin (10(-8) M) increased membrane fluidity markedly within 20 min. Membrane fluidity increased dose-dependently with increasing CCK stimulation. A supramaximal dose of cholecystokinin also induced bleb formation and increased LDH release. These phenomena were blocked by simultaneous incubation with CR1505 (Loxiglumide), a potent antagonist of peripheral cholecystokinin receptors. A supramaximal dose of carbachol (10(-3) M) also induced increases in the membrane fluidity. Pancreatic secretagogues that do not induce acute pancreatitis did not induce alterations in membrane fluidity. Lecithin increased both membrane fluidity and LDH release. These observations suggest that this increase in membrane fluidity of the pancreatic acini may be related to membrane alteration and to functional damage of the acini. These observations [correction of observation] can serve as a window to detect the development of acute pancreatitis at an early stage.     

Mechanism of gastric acid hypersecretion in patients with islet cell tumor without hypergastrinemia: studies in rats

BACKGROUND & AIMS: A nongastrin acid-stimulating peptide (NGASP) has been found in ulcerogenic pancreatic tumor syndrome without hypergastrinemia. The mechanism of gastric acid hypersecretion by NGASP was investigated in rats. METHODS: In vivo, gastric acid secretion and in vitro histamine release from enterochromaffin-like (ECL) cells in responses to tumor extract (TE) and synthetic human gastrin-17 I or pentagastrin (PG) were studied. Whether the 2 secretagogues potentiate each other was determined. RESULTS: TE dose-dependently stimulated histamine release, which was not blocked by a cholecystokinin (CCK)-B receptor antagonist. When TE was incubated with trypsin, the activity was abolished but was not affected by antibody. However, when rats were pretreated with antigastrin serum or CCK-B receptor antagonist, the acid secretion by TE was virtually abolished. The dose response of acid secretion to TE in the rats receiving PG in a threshold dose was significantly greater than that achieved by TE alone. Similarly, the dose response to PG combined with a threshold dose of TE was significantly greater than that produced by PG alone. CONCLUSIONS: NGASP stimulates histamine release from ECL cells, but the release is not mediated via CCK-B/gastrin receptor. NGASP and gastrin may potentiate each other to produce acid hypersecretion in ulcerogenic pancreatic tumor syndrome.     

Effect of L-364,718 (CCK receptor antagonist) on exocrine pancreatic secretion of adrenalectomized rats

The exocrine pancreatic secretion of control and adrenalectomized rats treated with L-364,718 was studied. The blockade of the action of endogenous cholecystokinin (CCK) in the control animals was reflected in a reduction of basal pancreatic secretion. This effect was reversed by the administration of submaximal doses of CCK-8. Under treatment with L-364,718, no decrease in pancreatic weight was observed. From this it may be deduced that factors other than CCK act on the pancreas to maintain the processes of enzyme synthesis and storage. Adrenalectomy reduced the weight of the pancreata; the main cause of this was the depletion of zymogen granules, which has been reported in adrenalectomized rats and is accompanied by a reduction in enzyme secretion, especially that of amylase. By contrast, the administration of L-364,718 from the very first moments after adrenalectomy leads to a retention of pancreatic enzymes. This effect is reflected in the maintenance of pancreatic weight and a secretory capacity in response to submaximal doses of CCK-8 similar to that of nonadrenalectomized animals. Accordingly, in the absence of glucocorticoids, endogenous CCK dominates the secretory process because when the action of this secretagogue is prevented by the administration of L-364,718, the discharge of proteins able to be secreted in response to a suitable stimulus is inhibited.