Long-term comparative effect of cholecystokinin and gastrin on mouse stomach, antrum, intestine, and exocrine pancreas

Mice were injected three times a day for 12 days with 300 micrograms/kg body weight of gastrin G17 or 37.5 Ivy dog U/kg body weight of CCK or saline. Other mice were also injected four times an hr for 1 hr with 7.5 micrograms/kg of gastrin, nine Ivy dog U/kg of CCK or saline; 1 hr before killing, they were injected with tritiated thymidine to evaluate the labelling indices in peptic, antral, duodenal, jejunal, and ileal mucosae. Four hours after the first injection of the two peptides, the peptic labelling indices increased while those of intestinal mucosa increased 8 hr after these injections. Long-term injections of CCK had a trophic effect on secretory cells of the digestive tract: the number of gastric zymogenic cells, Paneth cells, and the mucous cells of Brünner glands were hypertrophied. The pepsin, amylase, chymotrypsin, and lysozyme activities increased in stomach, exocrine pancreas, and intestine, respectively. Neither parietal cells nor intestinal enterocytes and hydrolase activities were affected. The trophic effect of long-term injections of gastrin is confirmed on parietal cells and exocrine pancreatic parenchyma and is demonstrated in Paneth cells. Confirming cytological results, pancreatic lipase and amylase activities and intestinal lysozyme activity were increased after gastrin. Although CCK and gastrin have a structural analogy, these two peptides did not affect the same cellular types. A specific action of CCK on the main secretory cells of the digestive mucosa is demonstrated.     

Long-term effect of somatostatin 14 on mouse stomach, antrum, intestine and exocrine pancreas

Mice were injected 3 times a day for 12 days with 8 micrograms/kg of somatostatin 14 which caused a hypoplasia of parietal and goblet cells, a hypotrophy and hypofunctionality of pancreatic acinar cells with a decrease in lipase and chymotrypsin activities, a decrease in the secretory fuction of the Brunner gland and in the number of dark granules of G cells. Neither villous and microvillous areas nor brush border hydrolase activities were affected. The number of peptic cells and Paneth cells increase as the level of pepsin and lysozyme. Mice were injected 4 times per hour with 2 micrograms/kg of somatostatin. 2 h after the first injection of somatostatin and 90 min after a single injection of tritiated thymidine, fundic, antral, jejunal and ileal labelling indexes strongly decrease (maximal effect in ileum). The inhibitory effect of somatostatin on the digestive epithelial cell proliferation compared to its long-term action only directed on specific cell types evokes probable compensatory mechanisms induced to maintain the equilibrium of the digestive epithelia.     

EFFECTS OF CHRONIC STEROID INGESTION ON GASTRODUODENAL EPITHELIAL RENEWAL IN THE RAT

Steroids may predispose to peptic ulcer formation. One possible mechanism could be via alteration of normal epithelial renewal. to study the effects of steroids on gastroduodenal epithelial renewal, rats received hydrocortisone sodium succinate in the drinking water to deliver a dose of 10 mg/kg per day. Control rats received plain water. After 4 weeks, the rats were injected intraperitoneally with tritiated thymidine, to label proliferating cells, and killed 1 hr later, to determine measurements of epithelial proliferation, or 24 hr later to determine measurements of epithelial migration. Sections of fundus, antrum and post-pyloric duodenum were processed for light microscopy and autoradiography. In fundic and antral mucosa, steroid treatment resulted in a reduction in the number of labelled cells and in the size of the proliferative zone and, in the fundus, the mucosal thickness was reduced. In the duodenum, although the number of labelled cells remained unchanged, steroid treatment did decrease the number of cells in the proliferative zone; further, crypt depth was reduced in steroid-treated rats, but villous height was increased, resulting in an overall increase in mucosal thickness. Epithelial migration was also depressed in fundic and antral mucosa, but appeared to be accelerated in the duodenum of steroid-treated rats. These studies indicate that although, in the duodenum, the effects of steroids on epithelial renewal are complex, in the stomach chronic steroid ingestion depresses epithelial renewal both in fundic and antral mucosa. This inhibition of epithelial renewal in the stomach may contribute to the ulcerogenic action of steroids by either rendering the mucosa susceptible to the effects of other ulcerogens or by retarding the healing of existing mucosal lesions.     

Effect of starvation on endocrine cells in the rat stomach

The influence of food deprivation on gastric G- and D-cells and on parietal cells was studied in the rat. In fed controls and groups of rats fasted for 12 and 96 h G-, D- and parietal cell densities, somatostatin and gastrin concentration in antral and fundic specimens and serum gastrin were compared. Gastrin in antral mucosa, serum gastrin, G-cell density as well as antral D-cell density decreased in long-term fasted rats by 52%, 90%, 58% and 42%, respectively. Fundic D-cell density remained unchanged. After 96 h starvation somatostatin concentration slightly increased in antral mucosa (+35%; P less than 0.05), but decreased in fundic mucosa (-40%; P less than 0.05). Parietal cell density was not influenced by prolonged fasting. These findings demonstrate that changes in D-cell morphology and mucosal somatostatin content are not parallel and that the rat gastric D-cell is less dependent on food in the gastric lumen than the G-cell. The unaltered fundic D-cell density reflects the functional activity of gastric D-cell which has also been shown to be independent of the presence or absence of food.     

亚东鲑消化系统的形态学和组织学观察

亚东鲑消化系统包括消化道和消化腺。消化道分为明显的食道、胃和肠等。食道粘膜为复层上皮,其中含有杯状细胞和味蕾,胃、肠粘膜为单层柱状上皮,其中散布较多的杯状细胞。消化腺包括肝脏和胰腺,肝小叶分界明显,胰腺外分泌部由腺泡组成,内分泌部即胰岛分散存在于外分泌部之间。     

Effect of myenteric denervation on intestinal epithelium proliferation and migration of suckling and weanling rats

The effects of myenteric denervation on the cell kinetics of the intestinal epithelium of suckling and weanling rats were investigated. The myenteric plexus of an ileal segment was partially ablated by serosal application of benzalkonium chloride (BAC) in three groups of rats: those that underwent surgery at 13 days and were killed 15 (13/28-day-old) or 23 (13/36-day-old) days after treatment, and those that were operated at 21 days (21/36-day-old) and were killed 15 days after treatment. The extent of denervation was assessed in whole-mount preparations. The cell bodies of myenteric neurones were stained by NADH-diaphorase histochemical technique. Cell proliferation was estimated by the mitotic index (MI) and morphometric analysis of villus and crypt lengths using an image analysis system. Thickness of the muscle layers was also assessed by morphometry. Cell migration on the villi was estimated by the position of the leading labelled cell 24 h after tritiated thymidine injection. The number of neurones was reduced by around 80% in rats operated at 13 days, and reduced by 98% in those operated at 21 days. The thickness of the muscle layers was increased in all groups of treated animals. MI was significantly higher 15 days after BAC-treatment in the 13/28 group. Morphological changes in the intestinal mucosa were observed 15 days after BAC-treatment, when there was an increase in villus height (13/28 group) and crypt depth (13/28 and 21/36 groups). Cell migration rate was accelerated in the 21/36 group. No differences where found in the 13/36 group. These results show the strong effect of myenteric ablation on cell proliferation and migration in the ileal epithelium in the first 15 days of treatment in suckling and in weanling rats, and the subsequent recovery of intestinal mucosa homeostasis later on.     

Calcitonin gene-related peptide neurons innervating the canine digestive system.

The pattern of nerve cells and fibers containing calcitonin gene-related peptide immunoreactivity (CGRP-IR) was investigated in the canine digestive tract by means of immunohistochemistry. CGRP-IR nerve fibers innervate all the layers of the gut, including the vasculature, with different densities depending on the region. CGRP-IR processes are sparse in the esophagus and stomach, where they are mostly confined to the enteric plexuses and vasculature. CGRP-IR fibers are quite abundant in the small and large intestine, where they form dense arborizations in the mucosa, and are numerous in the muscularis mucosae, deep muscular plexus and circular muscle. The myenteric and submucous plexuses of the intestine contain dense networks of CGRP-IR fibers and numerous CGRP-IR ganglion cells. On the other hand, in the enteric ganglia of the esophagus and stomach, in the intrapancreatic ganglia and in the ganglionated plexus of the gallbladder, CGRP-IR is restricted to non-varicose processes. A moderate density of CGRP-IR fibers supplies the endocrine and exocrine pancreas, and the fibromuscular layer and lamina propria of the gallbladder. The density of CGRP innervation in different regions can be summarized as follows: intestine > pancreas and gallbladder > or = antrum > cardia > gastric corpus and distal esophagus. CGRP- and tachykinin (TK)-IRs are colocalized in a substantial population of fibers, particularly those distributed to the mucosa, muscularis mucosae and vasculature, whereas there was no evidence of colocalization in intrinsic ganglion cells. The present results suggest that (1) the CGRP innervation of the dog digestive system includes an intrinsic and an extrinsic component, and (2) CGRP- and TK-IRs are co-expressed in extrinsic nerve fibers. These findings extend previous observations in rats and guinea pigs and provide insights into the sites of action of CGRP in the digestive system of the dog, which has served as a model for CGRP functional studies.     

Precocious cessation of intestinal macromolecular transport and digestive enzymes development by prostaglandin E2 in suckling rats

The effect of repeated oral administration of prostaglandin analogue (dmPGE₂) on intestinal macromolecular transport and digestive enzymes development were investigated in the suckling rats. By the administration of dmPGE₂ for 7 days, precocious induction of maltase activity, depression of amylase activity and enhancement of trypsin activity in the pancreas occurred. Absorption of bovine IgG was dose dependently depressed by drnPGE₂ treatments. The intestinal cessation was also observed in the adrenalectomized pups, but was not influenced by difluoromethyl ornithine administration. These results suggest that oral administration of PGE₂ induces precocious maturation of the small intestine and exocrine pancreas and that the intestinal cessation is not directly related to ornithine decarboxylase activity in the suckling rats.     

In vitro electrophysiological effects of cimetidine, prostaglandin E2 and acetylcholine on the rabbit gastric mucosa

The electrophysiological effects of cimetidine, cytoprotective dose of prostaglandin E2 (PGE2) and acetylcholine were determined in parallel in Ussing-chambered rabbit fundic and antral mucosal preparations. In the fundic mucosal preparations both cimetidine and PGE2 caused an increase in transmucosal potential difference (PD) and in short-circuit current (ISC); the transepithelial resistance (Rt) was essentially unchanged. Addition of acetylcholine to the pretreated fundic preparations produced further gradual increases in PD and ISC; cimetidine pretreatment delayed this effect of acetylcholine. In contrast to fundic mucosa, cimetidine did not cause any electrical change of the antral preparation but decreases in PD, Rt and ISC were detected after the addition of PGE2. Acetylcholine produced a rapid initial PD elevation followed by a PD drop of both antral tissues independent of pretreatment. These findings suggest that both cimetidine and PGE2 generated electrical hyperpolarisation of rabbit fundic mucosa. These changes may be favourable for mucosal protection. No "beneficial" electrical changes were detected on the antral mucosa after administration of cimetidine and PGE2. Acetylcholine increased the effects of other stimuli on the fundic mucosa. In the rabbit antral mucosa acetylcholine generated biphasic changes of electrical properties.     

Association of radiolabeled urogastrone binding with regenerating intestinal mucosa and epidermal growth factor/urogastrone producing organs in rat.

In the present study, we have tested the hypothesis that the regeneration of intestinal epithelium is regulated by changes in the uptake of radiolabeled recombinant human urogastrone (125I rhUG) in the regenerating mucosa and epidermal growth factor/urogastrone (EGF/URO) producing organs in the rats. Operations were performed on rats to approximate the ileal mucosa to the serosal surface of the cecum. This procedure allows the regeneration of ileal mucosa onto the serosal surface of the cecum. Groups of 5 rats were killed on the 2nd, 4th, 8th and 12th post-operative days. Two hours before autopsy, rats were given 0.5 ml (50 microCi with 30 micrograms protein) of 125I rhUG intravenously and the following tissues were removed: regenerating mucosa, salivary gland, duodenum, liver and kidney. Results indicated that the uptake of 125I rhUG was significantly greater in the salivary gland and duodenum on the 2nd post-operative day which gradually tapered with increasing time after surgery. A similar pattern in the uptake of 125I rhUG was also evident in the regenerating mucosa. Further analysis revealed a significant correlation between the uptake of 125I rhUG in the salivary gland and duodenum vs rate of epithelialization and uptake of 125I rhUG in the regenerative mucosa. These results suggested that the endogenous EGF/URO produced in the salivary gland and duodenum may be a factor in the regulation of intestinal regeneration; however, the mechanism responsible for reflex stimulation of EGF/URO production in these organs is not known.     

Marked increase in gastric histidine decarboxylase activity in patients with hypergastrinemia.

Histidine decarboxylase (HDC) activity and histamine content were measured in endoscopic gastric biopsy specimens of 19 control subjects with normogastrinemia and 6 patients with hypergastrinemia. In controls, the HDC activity was 3 fold higher in fundic mucosa (120 +/- 13 fmol/min/mg protein, mean +/- S.E.) than in antral mucosa (39 +/- 5 fmol/min/mg protein). In patients with hypergastrinemia, an extremely high HDC activity (713 +/- 181 fmol/min/mg protein) was observed in fundic mucosa, although the HDC activity in antral mucosa was not significantly different from that of controls. The histamine content in fundic mucosa was also significantly higher in patients with hypergastrinemia than in controls but no significant difference was seen in histamine content in antral mucosa between the two groups. These results are compatible with the hypothesis that in man, as well as in rat, histamine synthesis in fundic mucosa is enhanced by gastrin.     

Effect of short-term fasting/refeeding on epidermal growth factor content in the gastrointestinal tract of suckling rats.

Epidermal growth factor (EGF) is trophic for varying regions of the developing gastrointestinal tract (GIT) of suckling rats. The presence of large amounts of EGF in milk from various species, combined with low production of EGF by suckling animals, led to speculation that milk is a major source of EGF for suckling rats. We report that short-term fasting (8 hr) of 12-day-old suckling rats resulted in a significant decrease in the levels of immunoreactive EGF (irEGF) in the GIT. Pups refed by lactating mothers for 1 to 4 hr exhibited an increase in irEGF to original levels, whereas pups fed a rat milk substitute by gastric gavage did not have an increase in irEGF content. The irEGF levels in the GIT of pups that were manually fed normal rat milk, or rat milk substitute supplemented with EGF, returned to the prefasted levels. Fasted suckling rats refed 2 ml of rat milk in 2 h exhibited significantly higher level of irEGF in the GIT than did those refed with 0.5 ml in 45 min. Since rat milk irEGF exists in three distinct forms (A, B, and C; C is equal to authentic submandibular gland EGF, the irEGF forms in the GIT were characterized by native polyacrylamide gel electrophoresis. In the stomach luminal contents of the fed suckling rats, only the larger form, Peak B, was observed. Both the luminal content and the mucosa scrapings of all other segments of all groups contained only Form D (comigrating with desarginyl EGF), a metabolic derivative of EGF. All forms were immunoreactive, exhibited receptor binding, and stimulated DNA synthesis in growth-arrested fibroblasts. The rapid changes in EGF within the GIT of suckling rats suggest the EGF can acutely modify some GIT functions of suckling rats.     

Postnatal development of biliary and pancreatic exocrine secretion in piglets

1. The secretory responses of bile and exocrine pancreas were studied in various aged piglets. 2. At 3 days old the bile and exocrine pancreas could be reacted by various stimulations. The response by secretin was the same as that in the 28 day old. 3. Protein concentration in pancreatic juice by CCK-8 increased steeply after 6 days old, but the ratio of amylase to protein rose abruptly at 28 days old. 4. These findings indicate that (1) the secretory capacity of bile and pancreatic juice developed predominantly at an early period of postnatal life; (2) the formation of bile acids and pancreatic digestive enzymes developed gradually during the suckling period.     

Growth pattern of the polypeptide-YY cell population in the upper digestive tract of the rat during the perinatal period and after weaning

Summary The distribution of polypeptide-YY cells within the gastric and duodenal mucosa of the rat and the development of their populations were examined daily from 3 days before birth until day 8 postpartum and after weaning, on day 25 postpartum, using a precise technique of quantification. Polypeptide-YY cells appeared in the stomach around the 19th day of gestation. They were always more numerous in the antral mucosa and particularly in the pyloric sphincter area than in the fundic mucosa. Immunogold staining at the electron-microscopic level revealed that, in the antrum, polypeptide-YY was colocalised with gastrin in endocrine cells mainly of type G and, more rarely, in cells of intestinal type IG. Comparison of the gastrin and polypeptide-YY cell populations in the same rats indicated that, except at day 6 postpartum, there were fewer gastric polypeptide-YY cells than immunoreactive gastrin cells and that polypeptide-YY cells were 8 times less numerous than gastrin cells at day 25 postpartum. Polypeptide-YY cells were clearly present in the duodenum of the 19-day-old embryo. This population increases with age until day 8 postpartum, then significantly decreases (by 87%) between days 8 and 25 postpartum. Because polypeptide-YY may inhibit secretion of gastric acid, it is possible that the presence of significant population of polypeptide-YY cells in the upper digestive tract during the first postnatal week of life may play a role (endocrine or paracrine) in the decreased acid secretion occurring in the newborn rat.     

Cholecystokinin octapeptide induces both proliferation and apoptosis in the rat pancreas

Cholecystokinin-8 (CCK-8) causes exocrine pancreatic hypertrophy and hyperplasia. High doses of the CCK analogue cerulein causes necrosis and an inflammatory response in the pancreas. We have studied the pancreatic growth response in rats after administration of CCK-8 for 3 days, given either intermittently (20-80 microg/kg) twice a day, or continuously (2.4-48 microg/kg per 24 h). Plasma CCK-8 levels, pancreatic wet weight, water, protein and DNA contents and the pancreatic caspase-3 activity were measured. Cell proliferation was visualized by [3H]thymidine incorporation and apoptosis by TUNEL reaction. Continuous administration of CCK-8 dose-dependently increased the plasma CCK levels, the pancreatic wet weight, protein and DNA contents as well as thymidine labeling index, apoptotic index and caspase-3 activity. Intermittent injections of CCK-8 caused transient raises in plasma CCK, increased apoptotic index and caspase-3 activity, a dose-dependent increase in thymidine labeling but caused a dose-dependent reduction of pancreatic wet weight, protein, and DNA contents. It is concluded that CCK-8 causes both increased proliferation and apoptosis in the pancreas. In case of continuous administration of CCK-8, the proliferation outweighs the apoptosis causing hyperplasia but in the case of intermittent administration the opposite effect is seen.     

Processing and transfer of epidermal growth factor in developing rat jejunum and ileum

Using everted sac technique we demonstrated the transfer of ¹²⁵I-mEGF across the jejunal and ileal walls of suckling, weanling and adult rats. The transfer by the suckling rat jejunum and ileum was significantly inhibited by the presence of dinitrophenol and sodium azide or by the replacement of sodium with potassium or choline. RP-HPLC analysis detected carboxy-terminal processing of ¹²⁵I-mEGF in suckling and adult rat jejunum and ileum. Suckling rat jejunum produced ¹²⁵I-des(53)mEGF and ¹²⁵I-des(49–53)mEGF, whereas ¹²⁵I-des(48–53)mEGF was detected in suckling rat ileum or adult rat jejunum and ileum. All three forms of ¹²⁵I-mEGF bound to anti-EGF antibody and EGF receptors. The receptor binding of ¹²⁵I-des(53)mEGF was higher than that of ¹²⁵I-mEGF, but those of ¹²⁵-des(49–53)mEGF and ¹²⁵I-des(48–53)mEGF were greatly diminished. Results indicate a carboxy-terminal processing of mouse EGF during uptake and transfer in the small intestine of developing and adult rats, and the resulting products showed altered receptor binding. An identical amino acid sequence of the C-terminal pentapeptide of EGF from mouse, human and possibly rat may suggest a biological significance of C-terminal processing of EGF in the small intestine.     

Self-renewal of the human gastric epithelium: new insights from expression profiling using laser microdissection

The gastric mucosa is subject to continual bidirectional renewal by differentiation from stem and transit amplifying cells. It was the aim of this study to characterize the self-renewal of the human gastric mucosa and its two major types of glands in the fundus and antrum, respectively. Three characteristic regions (pit, proliferative, and lower neck regions) were isolated from fundic and antral units by the use of laser microdissection, and expression profiles concerning 15 marker genes were generated by RT-PCR analysis. The surface mucous cells (SMCs) of fundic and antral units differed in their expression of at least four secretory genes, i.e., gastric lipase, TFF3, FCGBP, and lysozyme. The maturation of mucous neck cells was shown to occur stepwise, first towards a mucous phenotype followed by a serous differentiation step. Also, a stepwise maturation of both the antral SMCs and antral gland cells was observed. Additionally, the presence of gastric lipase was also demonstrated for the first time in antral gland cells. In conclusion, the different expression profiles of SMCs of the fundic and antral units could be the basis for the different self-renewal rates of fundic and antral SMCs and could influence the spatial organization of the bacterial microbiota within the various parts of the gastric mucosa.     

Incorporation of radioactive proline and fucose in gastric mucosal biopsies. Correlation with histological findings

Human gastric mucosal biopsies incorporate in vitro radioactive proline and fucose into macromolecular glycoproteins (mucin). Differences were found between the incorporation pattern of antral and fundic mucosae according to their pathology, confirmed by histology. Antral mucosae with abnormal histology showed a significantly higher incorporation of proline than normal samples. Fucose incorporation was also increased. Similar results were found with fundic biopsies. The ratio of total fucose to total proline incorporated into mucin secreted during incubation also increased significantly in these samples. Biochemical analyses on the other hand showed no significant change. The results suggest a breakdown in the processing, storage and secretory processes of mucin-type glycoproteins in pathological mucosae, but not in their biosynthesis. The mucosal samples could be classified as A or B types according to their proline and fucose incorporation: A mucosae have a lower proline incorporation than B mucosae (greater than 380 cpm/micrograms DNA for the antrum and greater than 200 cpm/micrograms DNA for the fundus). These results confirm the possibility of studying abnormal mucus secretion using gastric biopsy samples.     

Preparation and properties of monoclonal and polyclonal antibodies to mouse epidermal growth factor (EGF) receptors: evidence for cryptic EGF receptors in embryonal carcinoma cells

Monoclonal antibodies to mouse epidermal growth factor (EGF) receptor were prepared by the immunization of rats with receptor glycoprotein purified from mouse liver by affinity chromatography on immobilized EGF. Purified mouse EGF receptor retained EGF-inducible autophosphorylating activity and was antigenic in rats and rabbits. The monoclonal antibodies cross react very poorly with human EGF receptor, while polyclonal rabbit antibodies immunoprecipitate human, rat and mouse EGF receptor equally well. The rabbit antibody blocks EGF binding to mouse fibroblast cells and, at 20-fold higher concentrations, stimulates uptake of tritiated thymidine into DNA. This indicates that antibodies bind at or close to the EGF-binding site and can mimic the effects of the growth factor. None of the monoclonals bind at the EGF site of the receptor. Immunoprecipitation, immunoblotting, 125I-EGF cross linking, 125I-surface labelling, immunohistochemistry and autophosphorylation techniques were used to delineate the basis for the induction of EGF receptors when OC15 embryonal carcinoma (EC) cells differentiate into endodermal derivatives (END). EGF-stimulated autophosphorylation of a 170 X 10(3) Mr protein in solubilized OC15 EC cells is readily detectable, although intact EC cells do not bind or respond to EGF by all other tests. The results suggest that cryptic EGF receptors are present in EC stem cells, a finding with implications in development.     

Announcement

Abstract

The Gastrin content has been estimated in the antral mucosae of male and female rats in different phases of the estrous cycle. Gastrin content appears to be highest in the rats at di‐estrous cycle end lowest in the rats at pro‐estrous. There is not much difference between the gastrin content at estrous and pro‐estrous. The gastrin content in the antral mucosa of male rats is higher than in rats a both estrous and pro‐estrous but it is about the same amount in rats at di‐estrous. The possible role of the circulating sex hormones on the storage of gastrin in the antral mucosa of rats has been discussed.