Analysis of the effects of food and of digestive secretions on the small intestine of the rat. 1. Mucosal morphology and epithelial replacement.
A modified Roux-en-Y repositioning of rat small intestine was performed so that the proximal segment of bowel (A) received only bile and pancreastic secretions, the second (B) received food direct from the stomach, and these two segments drained into a third (C). Four to five weeks after operation, cell production was assessed by injection of vincristine into operated, sham-operated and unoperated rats, and counts of blocked metaphases were made on isolated microdissected crypts. Villus height, crypt depth, and the number of crypts per villus (crypt/villus ratio) were also measured. Most of segment A showed no significant differences from sham-operated intestine, although the normal proximo-distal gradient of villus height was abolished. At the distal end (near the anastomosis with segments B and C), crypt depth and cell production were increased. The villus height gradient in segment B was also abolished, although crypt depth and cell production were significantly increased, especially at the proximal end. Crypt/villus ratio was also increased. Segment C showed all the characteristics of small bowel promoted to a more proximal position: increased villus height, crypt depth and cell production. Increased crypt/villus ratio was also observed. These results are discussed in terms of the role of food and of digestive secretions in the control of mucosal morphology and epithelial replacement. (+info)
Immunoreactive pancreatic Reg protein in sera from cystic fibrosis patients with and without pancreatic insufficiency.
BACKGROUND: The biological function of the Reg protein, a non-enzymic protein produced in fairly large amounts by pancreatic acinar cells, remains elusive. Its susceptibility to proteolysis leading to precipitation of the proteolysis product at neutral pH suggests that it could contribute to the protein plugging observed in cystic fibrosis (CF). AIMS: To study its behaviour in the serum of CF patients with or without pancreatic insufficiency and to compare it with that of other pancreatic secretory proteins. PATIENTS: 170 patients (93 with CF, 55 controls, and 22 with chronic pancreatitis) were studied. METHODS: Reg protein was measured using a specific enzyme immunoassay and its molecular form in CF sera was characterised by gel filtration. Molecular gene expression was investigated by dot-blot hybridisation. RESULTS: Reg protein was present in all CF sera studied from patients with or without pancreatic insufficiency, and in all cases the level was significantly higher than in controls. Its chromatographic behaviour in CF sera was identical with that of the protein present in normal serum. No correlation was found between the levels of Reg protein and trypsin(ogen) (or lipase) in CF, nor in control sera or normal pancreatic juice. Molecular gene expression of the corresponding proteins investigated in pancreatic tissues showed an absence of correlation between the mRNA levels. CONCLUSIONS: Reg protein may not be a secretory exocrine protein like the digestive enzymes but rather a hormone-like secretory substance with an endocrine or paracrine function. (+info)
COOH-terminally extended secretins are potent stimulants of pancreatic secretion.
Posttranslational processing of preprosecretin generates several COOH-terminally extended forms of secretin and alpha-carboxyl amidated secretin. We used synthetic canine secretin analogs with COOH-terminal -amide, -Gly, or -Gly-Lys-Arg to examine the effects of COOH-terminal extensions of secretin on bioactivity and detection in RIA. Synthetic products were purified by reverse-phase and ion-exchange HPLC and characterized by reverse-phase isocratic HPLC and amino acid, sequence, and mass spectral analyses. Secretin and secretin-Gly were noted to coelute during reverse-phase HPLC. In RIA using eight different antisera raised against amidated secretin, COOH-terminally extended secretins had little or no cross-reactivity. Bioactivity was assessed by measuring pancreatic responses in anesthetized rats. Amidated canine and porcine secretins were equipotent. Secretin-Gly and secretin-Gly-Lys-Arg had potencies of 81 +/- 9% (P > 0.05) and 176 +/- 13% (P < 0.01), respectively, compared with amidated secretin, and the response to secretin-Gly-Lys-Arg lasted significantly longer. These data demonstrate that 1) amidated secretin and secretin-Gly are not separable under some chromatographic conditions, 2) current RIA may not detect bioactive COOH-terminally extended forms of secretin in tissue extracts or blood, and 3) the secretin receptor mediating stimulation of pancreatic secretion recognizes both amidated and COOH-terminally extended secretins. (+info)
Detection of mutations of p53 tumor suppressor gene in pancreatic juice and its application to diagnosis of patients with pancreatic cancer: comparison with K-ras mutation.
Because of the difficulty in obtaining biopsy specimens from pancreatic cancer patients, K-ras mutation analysis in pancreatic juice has been used for specific diagnosis. But recently, false positives have been obtained with this method. To improve the genetic diagnosis of pancreatic cancer, detection of p53 gene mutation in pancreatic juice was studied. Pancreatic juice was sampled endoscopically. Single-strand conformation polymorphism analysis was used for p53 mutation analysis. Furthermore, K-ras mutations at codon 12 were also studied in the same pancreatic cancer patients. Of 26 cases of pancreatic cancer, p53 mutations were detected in 11 (42.3%). No mutations were seen in the cases with mucin-producing adenoma nor with chronic pancreatitis. K-ras mutations were detected in 84.0% of cases by RFLP analysis, which has high sensitivity, and in 65.3% by hybridization protection assay, which has high specificity. Using a combination assay with both genes, genetic abnormalities were detected in 92.0% by RFLP and 73.1% by hybridization protection assay including two cases in which p53 alone was positive by both methods. The specificity of p53 mutation for pancreatic cancer is very high. Therefore, simultaneous analysis of p53 and K-ras mutation is suggested to enhance the genetic diagnosis of pancreatic cancer. (+info)
Pharmacokinetics of 5-fluorouracil and its penetration into pancreatic juice in dogs.
AIM: To study the pharmacokinetic behavior of 5-fluorouracil (5-FU) in pancreatic juice in dogs and its correlation with 5-FU in plasma, and to evaluate its penetration characteristics. METHODS: After placing a pancreatico-drainage tube, 8 dogs were injected 5-FU 250 mg i.v. Blood and pancreatic samples were collected and the 5-FU concentrations were determined by HPLC. The pharmacokinetic parameters were obtained with statistical analysis. RESULTS: The mean slopes of the terminal phase (K10) in plasma and pancreatic juice were 9.4 h-1 and 10.2 h-1, respectively (P > 0.05). The pharmacokinetic behaviors of 5-FU in plasma and pancreatic juice fitted a nonlinear model. Its penetration index was 3.39 +/- 2.84. The penetration of 5-FU from blood to pancreatic juice was relatively rapid, demonstrating a consistently higher concentration in pancreatic juice than in plasma. CONCLUSIONS: The elimination phase of 5-FU in plasma was similar to that in pancreatic juice, indicating that they were in the same kinetic compartment. (+info)
Electrical physiological evidence for highand low-affinity vagal CCK-A receptors.
We have demonstrated that under physiological conditions CCK acts through vagal high-affinity CCK-A receptors to mediate pancreatic secretion. In this study, we evaluated the vagal afferent response to endogenous CCK in rats and defined the CCK-receptor affinity states and the vagal-receptive field responsive to CCK stimulation using electrophysiological studies. Experiments were performed on anesthetized rats prepared with bile-pancreatic fistula. Plasma CCK levels were elevated by diverting bile-pancreatic juice (BPJ). The single-unit discharge of sensory neurons supplying the gastrointestinal tract was recorded from the nodose ganglia. All units studied were either silent or they had a very low resting discharge frequency. Thirty-two single units were studied extensively; seven were shown to be stimulated by diversion of BPJ (2.6 +/- 2 impulses/min at basal to 40 +/- 12 impulses/min after diversion). Acute subdiaphragmatic vagotomy or perivagal capsaicin treatment abolished the response. The CCK-A-receptor antagonist CR-1409, but not the CCK-B antagonist L-365260, blocked the vagal response to endogenous CCK stimulation. Infusion of the low-affinity CCK-receptor antagonist CCK-JMV-180 completely blocked the vagal afferent response to the diversion of BPJ in three of seven rats tested but had no effect on the response in the remaining four. In a separate study, we demonstrated that gastric, celiac, or hepatic branch vagotomy abolished the response in different subgroups of neurons. In conclusion, under physiological conditions, CCK acts on both high- and low-affinity CCK-A receptors present on distinct vagal afferent fibers. The vagal CCK-receptor field includes the regions innervated by the gastric, celiac, and hepatic vagal branches. This study provides electrophysiological evidence that vagal CCK receptors are present on the vagal gastric, celiac, and hepatic branches and may occur in high- and low-affinity states. (+info)
Stimulative effect of a casein hydrolysate on exocrine pancreatic secretion that is independent of luminal trypsin inhibitory activity in rats.
We have previously demonstrated that proteins could stimulate pancreatic secretion independently of luminal bile-pancreatic juice (BPJ) in a BPJ-diverted rat. To determine whether luminal protease-independent pancreatic secretion occurs in normal rats with BPJ returned to the upper small intestine, we investigated the pancreatic secretory response to intraduodenal instillation of a casein hydrolysate or the synthetic trypsin inhibitor, FOY 305, at concentrations which could almost equally inhibit hydrolysis of the synthetic substrate for trypsin with the luminal content. FOY 305 at 10 micrograms/ml and casein hydrolysate solutions at both 100 and 200 mg/ml similarly inhibited approx. 80% of the tryptic activity in the luminal contents of the proximal small intestine. Intraduodenal administration of casein hydrolysate solutions (100 and 200 mg/ml) significantly increased pancreatic secretion in a dose-dependent manner. However, intraduodenal administration of FOY 305 (10 micrograms/ml) was ineffective for stimulating pancreatic secretion. These results demonstrate that dietary protein enhances pancreatic secretion independently of the masking of luminal trypsin activity in rats. (+info)
Canine pancreatic juice stimulates the release of secretin and pancreatic secretion in the dog.
A secretin-releasing factor (SRF) was found in canine pancreatic juice that increases plasma secretin and stimulates pancreatic secretion in rats, suggesting that a positive feedback mechanism may be involved in the regulation of pancreatic secretion. In the present study, we investigated to determine whether or not SRF releases endogenous secretin and stimulates exocrine pancreatic secretion in conscious dogs. Fresh pancreatic juice was collected from four dogs by intravenous administration of secretin at 0.5 microg. kg(-1). h(-1) and CCK at 0.2 microg. kg(-1). h. The juice was boiled for 10 min at 100 degrees C. Experiments were carried out in phase I of spontaneous cycle of interdigestive pancreatic secretion. The testing solutions were infused intraduodenally in separate experiments: NaHCO3 solution (0.1 M, 4.5 ml/min, 60 min), a corn oil (Lipomul, 2 ml/min, 10 min), boiled pancreatic juice (BPJ, 4.5 ml/min, 60 min), and mixture of BPJ and Lipomul. Pancreatic secretion of fluid and bicarbonate was significantly increased by either BPJ or a mixture of BPJ and Lipomul (34- and 31-fold or 41- and 38-fold, respectively). Plasma secretin level also significantly increased by 164.7 +/- 13.4% and 223.1 +/- 35.0%, respectively, from basal concentration of 1.7 +/- 0.5 pM. In contrast, neither bicarbonate solution nor Lipomul influenced the plasma secretin level or pancreatic secretion. In addition, when Lipomul was incubated with BPJ, no fatty acid was produced. Thus the increased pancreatic secretion in the dog infused with a combination of BPJ and Lipomul was caused by SRF in BPJ, which released endogenous secretin. Moreover, the increases by BPJ of both plasma secretin level and bicarbonate secretion were completely blocked by intravenous administration of an antisecretin antibody in these dogs. The observations suggest that SRF in pancreatic juice exerts a positive feedback effect on exocrine pancreatic secretion that is mediated by the release of secretin in the interdigestive state in dogs. (+info)