Time-course of changes in pancreatic size and enzyme composition in rats during starvation

Ultrastructural Mapping of the Zebrafish Gastrointestinal System as a Basis for Experimental Drug Studies

Research in the field of gastroenterology is increasingly focused on the use of alternative nonrodent model organisms to provide new experimental tools to study chronic diseases. The zebrafish is a particularly valuable experimental platform to explore organ and cell structure-function relationships under relevant biological and pathobiological settings. This is due to its optical transparency and its close-to-human genetic makeup. To-date, the structure-function properties of the GIS of the zebrafish are relatively unexplored and limited to histology and fluorescent microscopy. Occasionally those studies include EM of a given subcellular process but lack the required full histological picture. In this work, we employed a novel combined biomolecular imaging approach in order to cross-correlate 3D ultrastructure over different length scales (optical-, X-ray micro-CT, and high-resolution EM). Our correlated imaging studies and subsequent data modelling provide to our knowledge the first detailed 3D picture of the zebrafish larvae GIS. Our results provide unequivocally a limit of confidence for studying various digestive disorders and drug delivery pathways in the zebrafish.

Expression differences in mitochondrial and secretory chaperonin 60 (Cpn60) in pancreatic acinar cells

In pancreatic acinar cells, chaperonin Cpn60 is present in all the cellular compartments involved in protein secretion as well as in mitochondria. To better understand the role Cpn60 plays in pancreatic secretion, we have evaluated its changes under experimental conditions known to alter pancreatic secretion. Quantitative protein A-gold immunocytochemistry was used to reveal Cpn60 in pancreatic acinar cells. Cpn60 immunolabelings in cellular compartments involved in secretion were found to decrease in acute pancreatitis as well as upon stimulation of secretion and in starvation conditions. A major increase in Cpn60 was recorded in diabetic condition. This was normalized by insulin treatment. Although in certain situations changes in secretory enzymes and in Cpn60 correlate well, in others, nonparallel secretion seemed to take place. In contrast, expression of mitochondrial Cpn60 in acinar cells appeared to remain stable in all conditions except starvation, where its levels decreased. Expression of Cpn60 in the secretory pathway and in mitochondria thus appears to behave differently, and Cpn60 in the secretory pathway must be important for quality control and integrity of secretion.

Spontaneous and cholecystokinin-octapeptide-promoted regeneration of the pancreas following L-arginine-induced pancreatitis in rat

CONCLUSION

In L-arginine (Arg)-induced pancreatitis, evidence of acute inflammation was observed on d 1-3. Continuous tissue atrophy became visible at the sites of previous pancreatic necrosis, with simultaneous regeneration of the pancreas, mainly around the Langerhans islets. Administration of low doses of cholecystokinin-octapeptide (CCK-8) increased the inflammatory signs of pancreatitis in the early phase, but subsequently diminished the level of atrophy and accelerated the processes of regeneration in this model of pancreatitis.

BACKGROUND

The aim of this work was to study the regenerative processes following Arg-induced pancreatitis in rats. Besides the spontaneous regeneration, the effects of low doses of CCK-8 on the laboratory and morphologic parameters in this type of experimental pancreatitis were investigated.

METHODS

Male Wistar rats were divided into three groups. In group I, the rats received 200 mg/100 g body weight of Arg i.p. twice, at an interval of 1 h, and 0.5 mL saline was administered s.c. twice daily. In group II, besides the same amount of Arg, the rats received 1 microgram/kg of CCK-8 s.c. in 0.5-mL saline twice daily (7 AM and 7 PM). In the control animals (group III), an identical amount of glycine was administered i.p. instead of Arg at the same times. The rats were examined on d 1, 3, 7, 14, and 28 after pancreatitis induction. The pancreatic weight/body weight ratio (pw/bw) was calculated in each case. The serum levels of amylase, and glucose and the pancreatic contents of soluble protein, trypsin, amylase and DNA were determined, and histologic examinations were performed.

RESULTS

In groups I and II, both pw/bw (3.5 +/- 0.2 mg/g and 4.1 +/- 0.28 mg/g, respectively) and the serum amylase level (8900 +/- 560 IU/L and 11100 +/- 1390 IU/L, respectively) were significantly elevated on d 1 vs group III (2.1 +/- 0.06 mg/g and 5562 +/- 373 IU/L, respectively). Pw/bw was significantly decreased in groups I (0.96 +/- 0.12 mg/g, 0.8 +/- 0.1 mg/g, and 1.8 +/- 0.1 mg/g, respectively) and II (1.4 +/- 0.15 mg/g, 1.7 +/- 0.2 mg/g, and 1.95 +/- 0.1 mg/g, respectively) on d 7, 14, and 28 vs group III (2.6 +/- 0.3 mg/g, 3.1 +/- 0.15 mg/g, and 2.7 +/- 0.1 mg/g, respectively), whereas in group II it was significantly elevated vs. group I on d 7 and 14. The pancreatic contents of soluble protein, DNA, trypsin and amylase were significantly decreased on d 3-14 in groups I and II vs group III. The pancreatic DNA level was significantly elevated in group II (1.23 +/- 0.2 mg/pancreas) vs group I (0.7 +/- 0.1 mg/pancreas) on d 7. In group II, the soluble protein (73.1 +/- 15.5 mg/pancreas) and amylase (1104 +/- 160 IU/pancreas) levels were significantly elevated on d 14 as was that of trypsin (27.2 +/- 3.1 IU/pancreas) on d 28, vs group I (26.4 +/- 5.3 mg/p, 525 +/- 111 IU/pancreas, and 16.3 +/- 1.1 IU/pancreas, respectively). On histologic sections, the signs of acute inflammation of the pancreas were more pronounced in group II than in group I on d 1-3. After that time, in spite of the progressive atrophy of the pancreas, the signs of tissue repair were more expressed in group II.

Total parenteral nutrition affects the tropic effect of cholecystokinin on the exocrine pancreas

BACKGROUND

Cholecystokinin (CCK) exerts trophic effects on the exocrine pancreas. Total parenteral nutrition (TPN) results in hypotrophy of the pancreas. The present study aimed to examine the effect of exogenous and endogenous CCK during TPN.

METHODS

Seventy-two Sprague-Dawley rats were orally fed or given TPN after pancreaticobiliary diversion (PBD) and were infused with CCK-8S or the CCK-receptor antagonist devazepide for 7 days.

RESULTS

Infusion of CCK and PBD caused hyperCCKemia, whereas TPN did not influence the concentration of plasma CCK. The reduced pancreatic contents during TPN could be reversed by CCK but not by PBD. The hyperplastic response to CCK in orally fed rats was abolished during TPN. Devazepide did not influence the pancreatic variables in orally fed and TPN-treated rats.

CONCLUSION

TPN reduces the hyperplastic response of the exocrine pancreas to CCK, and CCK reverses the hypotrophy seen during TPN. The effects of CCK on the exocrine pancreas seems to need enteral nutrition for the full expression.

The changes in the rat parotid glands following total parenteral nutrition and pancreatico-biliary diversion are not mediated by cholecystokinin

CONCLUSIONS

The results of the present study suggest that the pancreas and parotid glands both respond with hypoplasia during absence of food in the digestive tract and with hyperplasia following pancreatico-biliary diversion (PBD). Factors other than cholecystokinin (CCK) are, however, involved in the effects on the parotid glands, since infusion of CCK-8S and devazepide was without influence.

BACKGROUND AND AIM

Total parenteral nutrition (TPN) causes reduced pancreatic weight, whereas PBD evokes hyperCCKemia and enlargement of the rat pancreas. The pancreas and parotid glands have in part similar morphology and function. Therefore, we studied the possible presence of alterations also in the parotid glands during TPN, after PBD and during infusion of sulfated cholecystokinin (CCK-8S) and the CCK-A receptor antagonist devazepide, respectively.

MATERIALS AND RESULTS

Rats either received TPN for 7 d, or were kept under otherwise identical conditions with free access to food and water. TPN markedly reduced both pancreatic and parotid wet weight and thereby also the protein and amylase contents, and pancreatic DNA content was decreased. There was a significant correlation between the pancreas and parotid glands when comparing these parameters. The concentration of plasma CCK was unaffected by TPN. PBD caused a sevenfold increase in plasma CCK and a three fold increase in the pancreatic weight compared to control rats 28 d after the operation. The protein and DNA contents in the pancreas were found to be increased. The parotid glands increased twofold in weight, but their protein and amylase contents were not affected. There was a significant correlation between the pancreas and parotid glands when comparing weight, and protein and amylase concentrations. Infusion of CCK-8S during 28 d caused a marked increase in pancreatic wet wt and protein and DNA contents. The CCK-A receptor antagonist devazepide induced a reduction in protein and DNA contents in the pancreas. The parotid glands were not affected by either treatment. No effect on the labeling index of serous and ductal cells of the parotid gland was seen at 36 h, 3, 7, and 28 d of infusion with CCK-8S or devazepide.

Pancreatic trophism in experimental liver cirrhosis

Pancreatic trophism and pancreatic enzyme composition, and plasma levels of cholecystokinin, insulin, glucagon, and glucose in liver cirrhosis induced by chronic thioacetamide administration (0.02% in the drinking water for 12 mo) were studied in rats. Advanced liver cirrhosis was evident in all thioacetamide-treated rats. The weight of the pancreas and its contents of DNA, protein, trypsinogen, chymotrypsinogen, proelastase, secretory trypsin inhibitor, and amylase were significantly increased as compared to the controls. The pancreatic secretory enzyme content changes showed a nonparallelism, characteristic of a cholecystokinin effect. Light and electron microscopy revealed a normal pancreatic architecture. Bioassayed plasma cholecystokinin levels in both fed and 24-h-fasted cirrhotic rats were significantly higher than in the corresponding controls. The plasma glucose, insulin, and glucagon levels demonstrated hypoglycemic tendencies with a glucagon predominance. These findings indicate that advanced liver cirrhosis in the rat is accompanied by pancreatic hypertrophy and hyperplasia, which might be attributed, at least in part, to elevated circulating cholecystokinin levels.

Experimental pancreatic hyperplasia and neoplasia: effects of dietary and surgical manipulation

Several studies carried out during the past two decades have investigated the effect of dietary and surgical manipulation on pancreatic growth and carcinogenesis. Diets high in trypsin inhibitor stimulate pancreatic growth and increase the formation of preneoplastic lesions and carcinomas in the rat pancreas. Cholecystokinin (CCK) is the key intermediary in this response, since both natural and synthetic trypsin inhibitors increase circulating levels of the hormone and CCK antagonists largely prevent these changes. Fatty acids enhance pancreatic carcinogenesis in both rats and hamsters, whereas protein appears to have a protective role in the rat, but to increase tumour yields in the hamster. Several surgical operations affect the pancreas. Pancreatobiliary diversion and partial gastrectomy stimulate pancreatic growth and enhance carcinogenesis, probably by means of increased CCK release. Complete duodenogastric reflux has similar effects on the pancreas but the gut peptide involved is gastrin. Although massive small bowel resection increases pancreatic growth, the marked reduction in caloric absorption probably explains its failure to enhance carcinogenesis. CCK and enteroglucagon might work in concert to modulate the tropic response of the pancreas to small bowel resection. In the pancreas, as in the large intestine, hyperplasia appears to precede and predispose to neoplasia.

Role of cholecystokinin in pancreatic adaptation to massive enterectomy

Since pancreatic adaptation to massive proximal small bowel resection (PSBR) may be modulated through cholecystokinin (CCK) secretion, we tested the effect of the CCK antagonist CR-1409 on this response. Male Wistar rats (n = 72) weighing 220-225 g were randomised to receive either PSBR or transection/resuture followed by saline or CR-1409 (12 mg/kg daily subcutaneously). Rats were killed one, two, and three weeks post-operatively, at which time blood was obtained for CCK assay and the pancreas was assessed for proliferative activity by three parameters: nucleic acid and protein content, bromode-oxyuridine (BrdUrd) labelling index, and proliferating cell nuclear antigen (PCNA) expression. PSBR increased plasma CCK concentration by 83-102% at 1-3 weeks, irrespective of CR-1409 administration. Total pancreatic DNA content per 100 g body weight increased by 34% at two weeks (p less than 0.05) and by 82% at three weeks (p less than 0.05), while RNA content increased by 60% and 178% (p less than 0.001) and protein content by 20% and 57% (p less than 0.05). PSBR increased the BrdUrd labelling index and the percentage of PCNA immunoreactive cells. CR-1409 completely abolished this proliferative response and also prevented the rise in nucleic acid and protein contents. Apart from growth stimulation, PSBR also enhanced pancreatic exocrine function, as shown by ultrastructural evidence of an appreciable decrease in zymogen granules; CR-1409 also inhibited this functional effect of hypercholecystokininaemia. The results confirm the tropic role of CCK after PSBR, and CR-1409 prevents this pancreatic adaptation.

Inhibitory effect of a cholecystokinin antagonist on the proliferative response of the pancreas to pancreatobiliary diversion

Since pancreatobiliary diversion probably stimulates pancreatic growth by increasing cholecystokinin secretion, the effect of the cholecystokinin antagonist CR-1409 on this adaptive response was tested. Male Wistar rats (n = 108) weighing 220-250g were randomised to receive either pancreatobiliary diversion (n = 60) or sham diversion (n = 48) and thereafter to receive either saline injections or CR-1409 (10 mg/kg/day, subcutaneously). Rats were killed at four, seven, and 14 days postoperatively, when blood was obtained for cholecystokinin assay and the pancreas was assessed for proliferative activity by three techniques: nucleic acid and protein assay, bromodeoxyuridine labelling, and metaphase arrest after vincristine administration (1 mg/kg, intraperitoneally). Pancreatobiliary diversion increased plasma cholecystokinin concentrations by 91% at seven days and 137% at 14 days, irrespective of CR-1409 treatment. Total pancreatic RNA content was doubled by pancreatobiliary diversion at four days (2.15 v 1.07 mg/100 g body weight: p less than 0.001) and at seven days (3.43 v 1.76 mg/100 g: p less than 0.001), and trebled at 14 days (4.27 v 1.32 mg/100 g: p less than 0.001). Pancreatobiliary diversion increased bromodeoxyuridine labelling index from 1.1 to 3.7% at seven days and the cell birth rate from 0.09 to 0.06%. CR-1409 completely abolished this proliferative response and partly prevented the rise in RNA. The results confirm pancreatic hypertrophy and increased acinar cell proliferation after pancreatobiliary diversion. CR-1409 prevents this adaptive growth, probably by blocking cholecystokinin receptors. Bromodeoxyuridine labelling and the metaphase arrest technique may be used to assess pancreatic cell kinetics.

Changes in pancreatic trophism and gene expression during a prolonged fasting period in rats

To examine the effects of fasting on trophism and gene expression in pancreas, adult male rats were deprived of food from 0-6 d. Total DNA, RNA, and proteins, and specific mRNAs for rat amylase, chymotrypsinogen B, trypsinogen I, proinsulin I, and actin (assessed by employing cloned cDNAs and dot-blot hybridization) were quantitated in pancreas. Body and pancreatic wt diminished progressively to reach 65 and 75% of initial values at the 6th d of fasting. Protein/DNA and total RNA/DNA ratios decreased 2.04 and 2.31-fold, respectively, during 6 d of fasting. The concentration of amylase, chymotrypsinogen B, trypsinogen I, and actin mRNA, expressed as cpm/microgram RNA, decreased significantly throughout the study period, whereas the decrease observed in Proinsulin I mRNA concentration was not significantly different. When mRNA concentrations were refereed to the total content of DNA, however, the decrease was significant for all messengers tested. It is concluded that the prolonged absence of nutrients in the digestive tract exerts negative trophic influence on pancreas and triggers differential changes in pancreatic gene expression. These changes are gradual, asynchronic, and nonparallel.

Mechanisms of action of alcohol administration on the trophic effect of soybean trypsin inhibitor and cholecystokinin octapeptide in rat

Influence of alcohol administration on the trophic effect of cholecystokinin-octapeptide and soybean trypsin inhibitor administration was examined in male Wistar rats. Two x 4 mL of 20% alcohol given intragastrically during 2 wk did not significantly influence pancreatic weight, DNA, protein, trypsin, chymotrypsin, amylase, lipase, or trypsin inhibitor contents of the pancreas. It diminished the hypertrophy but not the hyperplasia seen after CCK-8 treatment, and eliminated the hyperplasia, as well as the hypertrophy provoked by SBTI administration. Secretory studies and CCK measurements demonstrated decreased CCK release in response to SBTI stimulation after 3-d alcohol administration. The results indicate that alcohol inhibits the enzyme synthesis of the CCK stimulated dividing and/or newly formed acinar cells and the endogenous CCK release.