Disaccharidase activities after jejunoileal bypass in rat

Digestive enzymatic activities (maltase, lactase and sucrase) have been determined in the intestinal mucosa of rats subjected to a jejunoileal bypass of 45 cm. The weight and protein content of the mucosa (mg/cm) were significantly decreased in the bypassed segment and significantly increased in the unbypassed segment, as compared to control rats. Maltase, lactase and sucrase specific (U/g protein) and total activity (U/cm intestine) were significantly decreased in the bypassed jejunum, compared to sham-operated rats. In the ileum, maltase specific and total activities increased in bypassed animals while the lactase and sucrase activities remained unchanged.     

Enteral feedback control of pancreatic hypertrophy: the role of pancreatic biliary secretions

Chronic diversion of pancreatic and biliary secretions away from the proximal small intestine resulted in rapid increases in pancreatic size and protein content in adult rats. The effect was detectable as early as 10 days postsurgery. Differential changes in pancreatic enzymes were evident after bypass. The concentration of trypsinogen remained stable while amylase concentrations showed a marked decrease. Total pancreatic trypsinogen content, however, was increased, while amylase content remained similar to controls. Feeding bypassed rats with chows containing various pancreatic and biliary supplements had no effect on the hyperplastic response of their pancreata. Trypsinogen and amylase levels in supplemented groups remained similar to the bypassed group fed nonsupplemented chow, with the exception of increases in trypsinogen concentration and content in the groups supplemented with bile and cotazyme plus bile acids. The adequacy of oral refeeding of pancreatic biliary components was supported by its effectiveness in restoring mucosal enterokinase activity and trypsin levels in segment 1. However, there was no correlation between tryptic activity in the contents of the bypassed segment and the eventual pancreatic weight. These results indicate that factors other than those supplemented in this study are required in maintaining the steady state of pancreatic growth in normal rats.     

Mechanism for enterohepatic injury caused by circulatory disturbance of hepatic vessels in the rat

We reported previously that a transient occlusion followed by reperfusion of the portal vein and the hepatic artery of the rat significantly decreased the transhepatic transport of a cholephilic compound, and that this decrease was prevented by pretreating animals with poly(styrene co-maleic acid butyl ester)-conjugated superoxide dismutase (SM-SOD). To elucidate the mechanism for oxidative injury of the liver and the site for the generation of superoxide radicals, the effect of a portosystemic bypass on the liver function was examined in the rat whose hepatic vessels were temporarily occluded. A portosystemic bypass inhibited the reperfusion-induced decrease in hepatic transport of bromosulfophthalein as effectively as did SM-SOD. Kinetic analysis using 125I-labeled albumin revealed that the permeability of the small intestine markedly increased after a transient occlusion. The increase in intestinal permeability was also inhibited either by SM-SOD or by the portosystemic bypass. Xanthine oxidase activity in portal plasma markedly increased during occlusion and reperfusion, while it remained within normal ranges in the bypassed group. Thus, superoxide radical, and/or its metabolite(s), might play a critical role in increasing the intestinal permeability and in the pathogenesis of reperfusion-induced liver injury.     

The effect of massive small bowel resection (MSBR) and small intestinal bypass (JIB) in the rat on the enteroinsular axis

The effect of massive small bowel resection (MSBR) and jejuno-ileal bypass (JIB) on the enteroinsular axis in rats was compared. Glucose levels after an oral glucose tolerance test were determined in MSBR, JIB and control animals. The response of the beta-cell mass to glucose and gastric inhibitory polypeptide (GIP) was established in the same animals using the isolated perfused pancreas model. Immunocytochemical and morphological studies were performed to monitor the adaptive changes seen in the intestine of these animals. The glucose response to the oral glucose load was blunted in both test groups with the fasting GIP levels in the JIB group being elevated and the MSBR group being reduced. The response of the isolated perfused pancreas to GIP showed a marked (70%) reduction of insulin release in the JIB rats and a slight but non-significant reduction in the MSBR rats. In both groups the insulin response to glucose alone appeared normal. The area of the pancreatic islets and the percentage of the total area consisting of the four islet cell types (B, A, D, PP) were unchanged. In the intestine the GIP cells were markedly reduced in number in the jejunum of the functional intestine of the JIB rats and the jejunum from the MSBR rats. The GIP cells in the jejunum of the bypass loop did not differ from the control jejunum. The results indicate that the high basal GIP levels seen in the JIB rats were the result of GIP secreted from the blind loop. This study also confirmed the decreased sensitivity of the beta-cells to GIP after JIB while indicating that MSBR has little if any effect on the response of the beta-cell to GIP. These data presented further evidence that the high basal GIP levels were causally related to the decreased insulin response in the JIB rats.     

Responses of the exocrine pancreatic secretion to spontaneous feeding in rats with bile-pancreatic juice diversion

The regulatory response of the exocrine pancreas was examined in rats under unanesthetized and unrestrained conditions. The previous study demonstrated that the pancreatic protease secretion increased 2-fold after spontaneous feeding of a low protein diet in chronically bile-pancreatic cannulated rats (normal rats) whose bile-pancreatic juice (BPJ) was returned to the duodenum. In the present study, we observed the response of the exocrine pancreatic secretion to spontaneous feeding of a low protein diet in rats with chronic diversion of BPJ from the proximal small intestine for 6 days (bypass rat) whose diverted BPJ was returned to the upper ileum. During BPJ diversion, the dry weight and the protein content of the pancreas were increased 2-fold, compared with normal rats. Also, the levels of trypsinogen and chymotrypsinogen in the pancreas were increased several times, but amylase was decreased. The basal secretion of enzymes after a 24-hr fast was enhanced in bypass rats in proportion to the pancreatic enzyme contents. After spontaneous feeding of 8% casein fat-free diet, the increases in the pancreatic secretion of bypass rats were much smaller than those of normal rats. In contrast, the increase of BPJ flow of bypass rats after feeding was greater than that of normal rats. These findings represent that the chronic diversion of BPJ exerts hypergrowth of pancreas and hypersecretion of proteases in the fasting state, and less sensitivity of pancreatic enzyme secretion to dietary feeding.     

Kinetic parameters of maltose hydrolysis and glucose intake in the rat small intestine in a chronic experiment

"True" (corrected for the influence of the pre-epithelial layer) kinetic constants of maltose hydrolysis (Km and Vmax) and Glucose active transport (Kt and Jmax) in the isolated loop of the rat small intestine in chronic experiments were determined using a new mathematical approach. The Km (4.260.25 mM) does not differ from that, obtained in in vitro experiments on the homogenates of mucous membrane taken from the same intestinal loops, and the Vmax (0.72 +/- 0.07 mol/(min.cm)) is 1.7 times lower than that in in vitro experiments. The Kt and Jmax values are 3.18 +/- 0.68 mM and 0.73 +/- 0.07 mol/(min.cm), resp. The estimated values of Km, Kt and Vmax are in accordance with the corresponding published data, whereas the Jmax is several times higher than the value generally believed on the basis of acute experiments in vivo. A high level of glucose absorption in the small intestine of unanesthetized animals is achieved mainly due to a high permeability of the pre-epithelial layer and a high capacity of the active transport as a major mechanism of glucose absorption in the small intestine under normal conditions.     

Epithelial cell kinetics in the descending colon of the rat

The influence of experimental bypass on the epithelial cell kinetics in the rat descending colon was studied. It was found that the number of cells per crypt was markedly reduced at 6 weeks after bypass. The percentage of labelled crypt cells, 1 h after 3HTdR, and the distribution of labelled cells in the crypt was normal. Also the life span of the epithelial cells was the same in control and bypassed colon. The response of crypt cell proliferation to ischaemia-induced cell loss in the bypassed descending colon was similar to the one previously described for normal descending colon. This indicates that the absence of the normal luminal contents does not result in a different response of colonic crypts to induced cell loss. Furthermore, it was found that the number of cells per crypt and the proliferative activity did not change in the transverse colon after temporary ischaemia of the bypassed descending colon. This indicates that the increase in crypt cell proliferation after ischaemia-induced cell loss is a local response.     

Localization of pancreatic enzyme secretion-stimulating activity and trypsin inhibitory activity in zymogen granule of the rat pancreas

The intracellular localization of pancreatic enzyme secretion-stimulating activity in rat pancreas was investigated. We found and purified a pancreatic enzyme secretion-stimulating peptide from rat bile/pancreatic juice. The peptide is trypsin-sensitive (showing temporary trypsin inhibitory activity), and it is hypothesized that it acts as a trypsin-sensitive mediator in the feedback regulation of diet-induced pancreatic enzyme secretion. The zymogen granule fraction was purified 5-fold by ultracentrifugation by the Percoll density gradient method. The purity of the zymogen granule fraction was determined from the specific amylase activity and electron microscopic morphology. The specific enzyme activities of amylase and trypsin and the trypsin inhibitory activity increased in parallel during the purification, and the pancreatic enzyme secretion-stimulating activity was also localized in the zymogen granule fraction. These results suggest that the pancreatic enzyme secretion-stimulating peptide originates from the acinar cells, and that it is secreted through exocytosis of zymogen granules into the small intestine, its ratio to trypsin thus remaining constant. This idea supports our hypothesis that the stimulating peptide acts as a mediator for the feedback regulation of pancreatic enzyme secretion by trypsin.     

Effect of jejunoileal bypass in the rat on the enteroinsular axis

The effect of jejunoileal bypass (JIB) on the enteroinsular axis was studied in vivo and in vitro in the rat. Glucose, insulin and GIP responses to oral glucose were compared in JIB and control rats. The effect of glucose and GIP on insulin release from the isolated perfused pancreas of the same animals was investigated to determine if JIB altered the sensitivity of the beta cell. Immunocytochemical studies of gut and pancreas were also carried out. Glucose, insulin and GIP responses to a glucose load were blunted after JIB, although basal GIP levels were elevated in these animals. The insulin response of the perfused JIB pancreas to GIP was 70% reduced from controls although the insulin response to glucose appeared normal. The size and area of JIB islets were unchanged from controls as was the distribution of insulin, glucagon, somatostatin and pancreatic polypeptide. GIP immunoreactive cells were present in all regions of the intestine including the JIB blind loop. This study confirms the findings of others that a relationship exists between reduced GIP and insulin response to oral glucose after JIB, and indicates that a decrease in sensitivity of the beta cell to GIP occurs following JIB that is not rapidly reversible. GIP secreted from blind loop mucosa may contribute to the high basal GIP found in JIB rats and may be causally connected to the fall in beta cell sensitivity.     

Epostane and indomethacin actions on ovarian kallikrein and plasminogen activator activities during ovulation in the gonadotropin-primed immature rat.

Kallikrein and plasminogen activator (PA) are serine proteases that have been implicated in the ovulatory process. Epostane and indomethacin are anti-ovulatory agents that inhibit steroid and eicosanoid synthesis, respectively. This study examines the effects of these two anti-ovulatory agents on ovarian kallikrein and PA activities during ovulation. The proteases were assayed by their actions on chromogenic peptide substrates S-2266 and S-2251, respectively. The ovulatory process was induced in 25-day-old Wistar rats by giving them hCG (10 IU, s.c.) 2 days after the animals had been primed with eCG (10 IU, s.c.). Control animals ovulated approximately 60-70 ova/rat, with the first ova appearing in the oviducts at 10-12 h after hCG administration, and this was the same time ovarian kallikrein and PA activities reached a peak. When doses of epostane ranging from 0.1-5.0 mg/rat or doses of indomethacin ranging from 0.03 to 3.16 mg/rat were administered s.c. at 3 h after hCG, the two drugs inhibited ovulation and ovarian kallikrein and PA activities in a dose-dependent manner. However, the anti-ovulatory action of the two drugs was more closely correlated with suppression of kallikrein activity than with PA activity. Treatment of the animals with exogenous progesterone reversed the inhibitory action of epostane, but not of indomethacin. The results suggest that the increase in ovarian progesterone at the time of ovulation may influence ovarian kallikrein and PA activities.     

Proteinase,Lipase and Amylase Activities in the Small Intestine of Pigs Suffering from Colienterotoxaemia

The activities of proteinases, lipases, amylases and the activities of proteinase inhibitors, as well as the numbers of Escherichia coli in the contents from the small intestine were examined for pigs suffering from colienterotoxaemia and for healthy pigs. Enzyme activities were determined using an agar diffusion test. Compared with healthy animals the activities of proteinases and amylases in diseased animals were reduced while lipases showed increased activity. In pathologically changed contents showing large numbers of E. coli, proteinases could not be demonstrated; however, proteinase inhibitors were found in these contents. In healthy animals, proteinase inhibitors were not demonstrated in ingesta-con-taining contents. In diseased animals, E. coli were found in large numbers in all parts of the small intestine. In healthy animals, E. coli was demonstrated especially in the posterior part of the small intestine and regularly in small numbers. The possible influence of digestive enzymes, especially proteinases and their inhibitors, on enterotoxins from E. coli is discussed.     

Adenosine 3' , 5'-cyclic monophsphate phosphodiesterase activities in the x-irradiation induced rat small bowel adenocarcinoma.

The adenosine 3′, 5′-cyclic monophosphate phosphodiesterase (PDE) activities were evaluated in X-irradiation induced Holtzman rat small bowell adenocarcinoma and age-matched normal small intestine. Within normal small intestine, PDE activity was optimal at pH 7.4, and highly dependent upon the addition of Mg²⁺ or Mn²⁺. Analyses of the rat small bowel adenocarcinoma revealed significantly elevated PDE activities above the normal small bowel which were found to be relatively constant throughout the length of the ileum and jejunum. These findings suggest that the diminished intracellular adenosine 3′, 5′-cyclic monophosphate levels observed in this lesion (1) may be the consequence of elevated PDE activities.     

Chronic systemic treatment with epidermal growth factor in the rat increases the mucosal surface of the small intestine

We examined the effects of treatment with human recombinant epidermal growth factor (EGF) on the functioning small intestine in the rat. Male Wistar rats, 7–8 weeks old, were treated with EGF administered subcutaneously in doses of 0 (n = 7) or 150 μg/kg/day (n = 8) for 4 weeks. The histological composition and mucosal surface area of the perfusion-fixed small intestine was quantified with stereological principles. The length of the gut remained unchanged. The amount of tissue and surface area per length of gut (median (ranges)) were increased from 117 (101–131) mg/cm and 2.6 (2.1–3.5) cm²/cm in the controls to 146 (138–152) mg/cm and 3.5 (2.5–3.8) cm²/cm for the complete small intestine (both comparisons p < 0.02). The weight increase was due to mucosal growth in all parts of the intestine, whereas the surface area was only increased in proximal and middle parts. It is concluded that EGF treatment in rats increases the mucosal weight and surface area of the functioning small intestine.     

Effect of streptozotocin administration upon the serotonin content of the pancreas and small intestine of the rat

The study has examined the effect of streptozotocin-induced diabetes of 3 days and 10 weeks duration upon the serotonin content of the rat pancreas and small intestine. Streptozotocin administration (65 mg/kg) resulted in a significant (p less than 0.001) decrease in pancreatic serotonin after 3 days (to 18% of the non-diabetic content). Diabetes of both short- and medium-term duration had no significant effect upon the serotonin content of the small intestine suggesting that changes in mucosal serotonin levels are not responsible for the diarrhea frequently observed in streptozotocin-treated animals. The diabetogenic effect of streptozotocin and the reduction in pancreatic serotonin were abolished by prior injection of nicotinamide thus providing further evidence for co-storage of insulin and serotonin in the B cell.     

Ultrastructural changes in the rat exocrine pancreas after jejunoileal bypass

The influence of a 90% jejunoileal bypass on the rat exocrine pancreas was studied by morphometrical procedures. In sham-operated animals exocrine acinar cells accounted for 80.3% of the pancreas volume. These cells are composed of 9.9% nuclei, 8.4% mitochondria, 12.2% zymogen granules, 0.3% lipid droplets and 69.2% of a compartment ("ERGLS") composed of endoplasmic reticulum, ribosomes, Golgi areas, lysosomes and the cytoplasmic ground substance. Intestinal bypass did not change the volume density of exocrine cells nor that of nuclei in the cells during the three postoperative months. The means nuclear diameter was approximately the same in both groups. However, the volume density of secretory granules diminished by 50%. This was accompanied by a decrease in mean granular diameter, but not in their numerical density. The volume density of lipid droplets increased 10 fold, that of mitochondria increased slightly from the 15th postoperative day but significantly from the 45th day. The remaining cellular compartment composed of "ERGLS" was not modified by intestinal bypass. These findings suggest that a 90% jejunoileal bypass induces major changes in the composition of pancreatic acinar cells but not in their size.     

Intestinal goblet cell mucus release. II. In vivo stimulation by antigen in the immunized rat.

We previously reported that the infusion of certain soluble immune complexes stimulated mucus release from the rat small intestine in vivo. The present studies sought to evaluate the response of the intestine of normal and immunized rats to the infusion of antigen alone. One hour after the intraduodenal infusion of antigen, small intestinal washings were obtained and analyzed for the presence of 35S-labeled, high m.w. glycoprotein of goblet cell origin. The amount of goblet cell glycoprotein released was estimated from the radioactivity present in the void volume of a Sepharose 4B gel filtration column. The release of goblet cell mucus was enhanced by antigen stimulation in orally immunized animals. The discharge of goblet cell mucus was not increased after antigen infusion in animals immunized by the i.p. route despite the induction of high levels of serum antibody. The inability to demonstrate release of mucus after antigen challenge in systemically immunized rats suggests that the amount or the type(s) of antibody required at the mucosal surface is produced only after oral immunization.     

Walker 256 tumour growth causes marked changes of glutamine metabolism in rat small intestine

The effect of Walker 256 tumour growth on the metabolism of glucose and glutamine in the small intestine of rats was examined. Walker 256 tumour has been extensively used as an experimental model to induce cancer cachexia in rats. Walker 256 tumour growth decreased body weight and small intestine weight and length. The activities of glucose-6-phosphate dehydrogenase and phosphate-dependent glutaminase were reduced in the proximal, median and distal portions of the intestine. Glutamine oxidation was reduced in the proximal portion only. The decrease in glutaminase activity was not due to a low synthesis of the protein as indicated by Western blotting analysis. Hexokinase and citrate synthase activities were not changed by the tumour. These findings led us to postulate that tumour growth impairs glutamine metabolism of small intestine but the mechanism involved remains to be elucidated.     

Influence of nitrate and nitrite on electrolyte transport by the rat small and large intestine

1. The influence of nitrate and nitrite on net absorption of electrolytes (Na+, K+, Cl-) and water from ligated loops was studied at various intestinal sites in rats. 2. Nitrate strikingly reduced Cl- absorption in rat proximal and distal colon, whereas Na+ absorption was reduced only moderately. Nitrite also reduced Cl- absorption in the colon. 3. Nitrate showed no significant effect on electrolyte absorption in the small intestine. 4. The results suggest that Cl-/HCO3- on exchange is the major route of Cl- absorption in the colon, whereas this mechanism seems not to be of importance for Cl- absorption by the small intestine.