Hormonal regulation of the fish gastrointestinal tract

The gastrointestinal tracts (GIT) of fish and other vertebrates are challenged with a diversity of functional demands caused by changes and differences in dietary inputs and environmental conditions. This contribution reviews how hormonal regulation plays an essential role in modulating the GIT functions of fish to match changes in functional demands. Exemplary is how hormones produced by the GIT, the associated organs (e.g., pancreas), and other sources (e.g., hypothalamus, adrenal cortex, thyroid, gonads) modulate the digestive processes (motility, secretion, and nutrient absorption) in response to dietary inputs. Hormones regulate the other GIT functions of osmoregulation (secretion and absorption of electrolytes and water), immunity, endocrine secretions, metabolism, and the elimination of toxic metabolites and environmental contaminants to match changes in environmental conditions and physiological states. Although the regulatory molecules and associated signaling pathways have been conserved during evolution of the vertebrate GIT, the specific responses often vary among fish with different feeding habits and from different environments, and can differ from those described for mammals.     

Endotoxin-like effects in acute phase response to Trypanosoma brucei brucei infection are not due to gastrointestinal leakage

Trypanosomosis is mainly an immunological and inflammatory response mediated by increased levels of pro-inflammatory cytokines. Evidence suggests that pathological changes produced during infection with trypanosomes could be initiated by nonspecific endotoxin-like substances in trypanosomes and/or Gram-negative secondary bacterial infection. Studies in trypanosome-infected rats indicate damage to the gastrointestinal tract (GIT) accompanied by increased leakage of the GIT mucosa. The current study was carried out to determine the in vivo response to endotoxin-like substances of Trypanosoma brucei brucei. To this purpose we neutralized the entrance of endotoxin through the GIT using polymyxin-B treatment and monitored the plasma concentration of the acute phase proteins SAP and Hp. The results in this study, where infection was performed in the presence of oral antibiotic that is not absorbed from GIT and which binds to and inactivates endotoxin, show that the elevated plasma levels of endotoxin-like activity and the resulting acute phase response indicated by an increase in levels of Hp and SAP, are due to trypanosome infection. Results obtained in the present study indicate that GIT is not the major source of elevated plasma endotoxin-like activity levels and the observed acute phase response was due to an increase in the levels of acute phase proteins SAP and haptoglobin.Therefore trypanosomes are responsible for the elevated plasma endotoxin-like activity levels and the subsequent systemic acute phase response in the host.     

Effect of glucose infusion on venous blood levels of immunoreactive proinsulin activity, insulin activity and fat parameters in healthy and protodiabetic subjects.

Concentrations of immunoreactive insulin activity (IRI) and proinsulin activity (IRP), blood glucose, free fatty acids (FFA), glycerol, cholesterol, triglycerides were analyzed in 140 subjects suspect of protodiabetes and 50 healthy persons before, during and after a glucose infusion test (GIT). The protodiabetic subjects were classified into normweight, overweight, obese, hyperlipemic groups with diet or with Regadrin therapy and each of them subdivided into such with normal and such with pathological carbohydrate tolerance. Norm- and overweight subjects with asymptomatic diabetes were characterized by a significant reduction of insulin secretion during both phases. Obese patients with or without hyperlipoproteinemia demonstrated an increased IRI reaction during the late phase of secretion. Carbohydrate intolerance was associated with an enhancement of basal triglyceride levels and a reduced depression of glycerol and FFA during the GIT. There were no differences in fasting or reactive IRP concentrations between healthy and protodiabetic subjects with normal carbohydrate tolerance. In asymptomatic diabetes the IRP levels were increased during the late secretion phase, but the percentage of IRP in total IRI was normal or--in existing high response--significantly reduced in comparison to norm response. The results do not support an enhanced IRP secretion as the cause of carbohydrate intolerance.     

Contribution of postexercise increment in glucose storage to variations in glucose-induced thermogenesis in endurance athletes

The present study was undertaken to evaluate the contribution of an increment in glucose storage to the reduced glucose-induced thermogenesis (GIT) characterizing endurance-trained individuals. For that purpose, glucose storage and GIT were determined during an oral glucose tolerance test (OGTT) in eight elite endurance athletes exercising between 6 and 16 h/week. Their values were compared with those obtained in five nontrained subjects submitted to two OGTT, i.e., before and 16 h after they had performed a 90-min vigorous exercise. As expected, endurance athletes exhibited a reduced GIT and a greater glucose storage during the OGTT in comparison to the preexercise values of nontrained subjects. Once the latter subjects had performed the 90-min exercise, their glucose storage during the OGTT was similar to the level found in athletes. This adaptation was accompanied by a significant reduction in GIT, which corresponded to 47% of the difference observed between trained and nontrained subjects when both groups maintained their usual life habits. Unlike GIT, resting metabolic rate (RMR) was found to be higher in athletes than in nontrained individuals. When subdividing the athletes into two subgroups on the basis of the duration of their weekly training, it was found that RMR was mainly elevated in those performing the higher amount of exercise. These results demonstrate that the reduced GIT characterizing endurance-trained individuals is partly explained by an increase in glucose storage during an OGTT. As further discussed, this reduced GIT is likely an indirect consequence of modifications of other energy-requiring energy processes rather than a direct result of the postexercise increment in glucose storage.     

The cytoskeletal regulatory scaffold protein GIT2 modulates mesenchymal stem cell differentiation and osteoblastogenesis

G protein-coupled receptor kinase interacting protein 2 (GIT2) is a signaling scaffold protein involved in the regulation of cytoskeletal structure, membrane trafficking, and G protein-coupled receptor internalization. Since dynamic cytoskeletal reorganization plays key roles both in osteoblast differentiation and in the maintenance of osteoclast polarity during bone resorption, we hypothesized that skeletal physiology would be altered in GIT2(-/-) mice. We found that adult GIT2(-/-) mice have decreased bone mineral density and bone volume in both the trabecular and cortical compartments. This osteopenia was associated with decreased numbers of mature osteoblasts, diminished osteoblastic activity, and increased marrow adiposity, suggesting a defect in osteoblast maturation. In vitro, mesenchymal stem cells derived from GIT2(-/-) mice exhibited impaired differentiation into osteoblasts and increased adipocyte differentiation, consistent with a role for GIT2 in mesenchymal stem cell fate determination. Despite elevated osteoclast inducing cytokines and osteoclast numbers, GIT2(-/-) mice also exhibit impaired bone resorption, consistent with a further role for GIT2 in regulating osteoclast function. Collectively, these findings underscore the importance of the cytoskeleton in both osteoblast and osteoclast function and demonstrate that GIT2 plays essential roles in skeletal metabolism, affecting both bone formation and bone resorption in vivo.     

O3浓度升高对小麦根际土壤酶活性和有机酸含量的影响

近地层臭氧(O₃)浓度升高作为全球气候变化的重要因素之一,对土壤生态环境和农作物生长发育造成了很大影响.本研究采用开顶式气室(OTCs)法,探究臭氧浓度升高对小麦不同生育期(分蘖期、拔节期、孕穗期和成熟期)根际土壤酶活性(过氧化氢酶、多酚氧化酶、脱氢酶和转化酶)和有机酸含量(草酸、柠檬酸和苹果酸)的影响规律,并结合根际土壤理化性质、植株根系生长状况等分析其产生影响的原因.结果表明: O₃浓度升高不同程度地提高了小麦成熟期土壤过氧化氢酶、多酚氧化酶、脱氢酶和转化酶活性,其中过氧化氢酶和多酚氧化酶活性提高达显著水平;在抽穗期,脱氢酶和转化酶活性因臭氧浓度升高而显著提高,增幅最高可达76.7%.在成熟期,O₃浓度升高显著提高了根际土壤中柠檬酸和苹果酸含量;显著降低了根际土壤pH、电导率、总碳和总氮含量,增加了土壤氧化还原电位(Eh);显著降低了小麦根系生物量、总根长和根总表面积,而增加了根平均直径.     

Regulation of neuroendocrine exocytosis by the ARF6 GTPase-activating protein GIT1

Neuroendocrine cells release hormones and neuropeptides by exocytosis, a highly regulated process in which secretory granules fuse with the plasma membrane to release their contents in response to a calcium trigger. Using chromaffin and PC12 cells, we have recently described that the granule-associated GTPase ARF6 plays a crucial role in exocytosis by activating phospholipase D1 at the plasma membrane and, presumably, promoting the fusion reaction between the two membrane bilayers. ARF6 is activated by the nucleotide exchange factor ARNO following docking of granules to the plasma membrane. We show here that GIT1, a GTPase-activating protein stimulating GTP hydrolysis on ARF6, is the second molecular partner that turns over the GDP/GTP cycle of ARF6 during cell stimulation. Western blot and immunofluorescence experiments indicated that GIT1 is cytosolic in resting cells but is recruited to the plasma membrane in stimulated cells, where it co-localizes with ARF6 at the granule docking sites. Over-expression of wild-type GIT1 inhibits growth hormone secretion from PC12 cells; this inhibitory effect was not observed in cells expressing a GIT1 mutant impaired in its ARF-GTPase-activating protein (GAP) activity or in cells expressing other ARF6-GAPs. Conversely reduction of GIT1 by RNA interference increased the exocytotic activity. Using a real time assay for individual chromaffin cells, we found that microinjection of GIT1 strongly reduced the number of exocytotic events. These results provide the first evidence that GIT1 plays a function in calcium-regulated exocytosis in neuroendocrine cells. We propose that GIT1 represents part of the pathway that inactivates ARF6-dependent reactions and thereby negatively regulates and/or terminates exocytotic release.     

Morphofunctional state of the digestive tract in the early stages of atherosclerosis]

Cholesterol, alpha- and beta-lipoproteids, serotonin were determined in the blood serum of dogs which were on atherogenic diet for 2 months. The serotonin content was examined in various parts of the gastrointestinal tract (GIT). Parallel studies of the structural changes were carried out in the vascular system (VS) and various parts of the GIT. There was found a direct correlation between a rise in the cholesterol and serotonin level in the blood and serotonin in the GIT tissues. The initial stages of atherosclerotic changes were revealed in the vascular system. Along with compensatory-adaptive changes detected in the duodenum and the upper protions of the small intestine, initial stages of dystrophic-atrophic processes were observed in the lower portions. Comparative analysis of biochemical and morphological data indicated that disturbances of the morphofunctional state in the GIT played an important role in the genesis of the early stages of atherosclerosis.     

Gastric acid secretion in streptozotocin-diabetic rats--different responses to various secretagogues.

We compared gastric acid secretion in response to various stimuli in normal and streptozotocin (STZ)-induced diabetic rats, in an attempt to characterize the alteration of acid secretory response in diabetic conditions. Animals were injected STZ (70 mg x kg(-1), i.p.) and used after 5 weeks of diabetes with blood glucose > 350 mg x dL(-1). Under urethane anesthesia, a rat stomach was mounted on an ex vivo chamber, perfused with saline and acid secretion was measured at pH 7.0 using a pH-stat method and by adding 100 mM NaOH. The acid secretion was stimulated by i.v. infusion of either histamine (4 mg x kg(-1) x h(-1)), pentagastrin (60 microg x kg(-1) x h(-1)) or carbachol (20 microg x kg(-1) x h(-1)) or i.v. injection of YM-14673 (0.3 mg x kg(-1)), an analog of thyrotropin-releasing hormone, or vagal electrical stimulation (2 ms, 3 Hz, 0.5 mA). In normal rats, gastric acid secretion was increased in response to either histamine, pentagastrin, carbachol, YM-14673 or electrical vagal stimulation. In STZ diabetic rats, however, changes in acid secretion varied depending on the stimuli; the acid secretory responses to histamine remained unchanged, those to YM-14673 and vagal electrical stimulation significantly decreased, but the responses to both pentagastrin and carbachol were significantly enhanced as compared to normal rats. Luminal release of histamine in response to both pentagastrin and carbachol was increased in STZ-diabetic rats as compared to normal animals. The altered acid secretory responses in STZ diabetic rats were partially reversed by daily injection of insulin with amelioration of high blood glucose levels. These results suggest that STZ-diabetic rats showed different changes in gastric acid secretory responses to various stimuli; no change in response to histamine, a decrease to both YM-14673 and vagal electrical stimulation and an increase to both pentagastrin and carbachol. The increased acid secretory response may be associated with an enhanced release of mucosal histamine, while the decreased response may be due to vagal neuropathy.     

Comparison between the oral glucose tolerance test and the glucose infusion test in the characterization of protodiabetes]

Within 3 days the 2-hour glucose infusion test (GIT) and the 50gm oral glucose tolerance test (oGTT) were performed in 113 normal weight and 33 obese persons suspected to protodiabetes and in 14 control subjects respectively. The results are compared with criteria from a group of healthy persons without any heredity of diabetes worked out in our laboratory. In about 66 per cent of the investigated subjects a concordance between both tests could observed in carbohydrate tolerance. Abnormal results were found more frequently after the oral glucose application. From these finding it was concluded a higher sensitivity of the oGTT. On the other hand followup studies of the disagreed diagnosis have shown that in 91 per cent the test results of the GIT were reproduced. The insulin secretion pattern agreed in 70 per cent between both tests. Whereas the insulin secretion pattern during the oGTT does not allowed to differ between the groups using the glucose infusion test we were able to observe a significant diminished hormone release in the initial as well as in the late phases, if the carbohydrate tolerance was pathologically. Summarizing the results we concluded that the GIT is characterized by a good reproducibility and a higher diagnostic importance than the 50 gm oGTT.     

Diet-induced obesity suppresses ghrelin in rat gastrointestinal tract and serum

The aims of the present study were to examine ghrelin expression in serum and gastrointestinal tract (GIT) tissues, and to measure tissue ghrelin levels and obesity-related alterations in some serum biochemical variables in rats with diet-induced obesity (DIO). The study included 12 male rats, 60 days old. The rats were randomly allocated to two groups (n = 6). Rats in the DIO group were fed a cafeteria-style diet to induce obesity, while those in the control group were fed on standard rat pellets. After a 12 week diet program including an adaptation period all rats were decapitated, tissues were individually fixed, ghrelin expression was examined by immunohistochemistry , and tissue and serum ghrelin levels were measured by radioimmunoassay. Serum biochemical variables were measured using an autoanalyzer. When the baseline and week 12 body mass index and GIT ghrelin expression were compared between DIO and control rats, BMI had increased and ghrelin expression decreased due to obesity. The RIA results were consistent with these findings. Serum glucose, LDL cholesterol, and total cholesterol levels were elevated and HDL cholesterol significantly decreased in the DIO group. A comparison of GIT tissues between the control and obese groups demonstrated that ghrelin was decreased in all tissues of the latter. This decrease was brought about a decline in the circulating ghrelin pool. This suggests that rather than being associated with a change in a single tissue, obesity is a pathological condition in which ghrelin expression is changed in all tissues.     

Correlation between electrical activity and ACTH/beta-endorphin secretion in mouse pituitary tumor cells

The electrical and secretory activities of mouse pituitary tumor cells (AtT-20/D-16v), which contain and release the ACTH/beta-endorphin family of peptides, were studied by means of intracellular recordings and radioimmunoassays. Injection of depolarizing current pulses evoked action potentials in all cells and the majority (82%) displayed spontaneous action potential activity. Action potentials were found to be calcium-dependent. Barium increased membrane resistance, action potential amplitude and duration, and release of ACTH and beta- endorphin immunoactivity. Isoproterenol increased both action potential frequency and hormone secretion. Raising the external calcium concentration increased the frequency and amplitude of the action potentials and stimulated secretion of ACTH and beta-endorphin immunoactivity. Thus, stimulation of secretory activity in AtT-20 cells was closely correlated with increased electrical activity. However, a complete blockade of action potential activity had no effect on basal hormone secretion in these cells. These results suggest that the mechanisms underlying stimulated hormone secretion are different from those responsible for basal secretory activity. It is proposed that the increased influx of calcium due to the increased action potential frequency initiates the stimulated release of hormone from these cells.     

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.     

Nonlatent and latent hepatic glutathione-insulin transhydrogenase activity during perinatal development and liver regeneration in rats and in rat placenta

We have studied glutathione-insulin transhydrogenase (GIT) activity in differentiating rat liver during parturition and neonatal growth and during compensatory liver growth. Parturition is characterized by a rapid but transient increase in total (i.e., nonlatent plus latent) hepatic GIT activity resulting from changes in the quantity (Vm) of the enzyme while neonatal growth is characterized by an increase in the nonlatent (active) form which persists until just prior to weaning. During liver regeneration following partial hepatectomy, GIT activity/mg protein is lowest after 12 h of regeneration and then progressively increases exceeding the control levels after 72 h of regeneration. Placenta from near-term rats contain a significant concentration of GIT which is immunologically similar to hepatic GIT.     

Resveratrol supplementation restores high-fat diet-induced insulin secretion dysfunction by increasing mitochondrial function in islet

Resveratrol (RSV), a natural compound, is known for its effects on energy homeostasis. Here we investigated the effects of RSV and possible mechanism in insulin secretion of high-fat diet rats. Rats were randomly divided into three groups as follows: NC group (animals were fed ad libitum with normal chow for 8 weeks), HF group (animals were fed ad libitum with high-fat diet for 8 weeks), and HFR group (animals were treated with high-fat diet and administered with RSV for 8 weeks). Insulin secretion ability of rats was assessed by hyperglycemic clamp. Mitochondrial biogenesis genes, mitochondrial respiratory chain activities, reactive oxidative species (ROS), and several mitochondrial antioxidant enzyme activities were evaluated in islet. We found that HF group rats clearly showed low insulin secretion and mitochondrial complex dysfunction. Expression of silent mating type information regulation 2 homolog- 1 (SIRT1) and related mitochondrial biogenesis were significantly decreased. However, RSV administration group (HFR) showed a marked potentiation of glucose-stimulated insulin secretion. This effect was associated with elevated SIRT1 protein expression and antioxidant enzyme activities, resulting in increased mitochondrial respiratory chain activities and decreased ROS level. This study suggests that RSV may increase islet mitochondrial complex activities and antioxidant function to restore insulin secretion dysfunction induced by high-fat diet.     

The elevation of glutamate content and the amplification of insulin secretion in glucose-stimulated pancreatic islets are not causally related

Glucose increases insulin secretion by raising cytoplasmic Ca(2+) ([Ca(2+)](i)) in beta-cells (triggering pathway) and augmenting the efficacy of Ca(2+) on exocytosis (amplifying pathway). It has been suggested that glutamate formed from alpha-ketoglutarate is a messenger of the amplifying pathway (Maechler, P., and Wollheim, C. B. (1999) Nature 402, 685-689). This hypothesis was tested with mouse islets depolarized with 30 mm KCl (+ diazoxide) or with a saturating concentration of sulfonylurea. Because [Ca(2+)](i) was elevated under these conditions, insulin secretion was stimulated already in 0 mm glucose. The amplification of secretion produced by glucose was accompanied by an increase in islet glutamate. However, glutamine (0.5-2 mm) markedly augmented islet glutamate without affecting insulin secretion, whereas glucose augmented secretion without influencing glutamate levels when these were elevated by glutamine. Allosteric activation of glutamate dehydrogenase by BCH (2-amino 2-norbornane carboxylic acid) lowered islet glutamate but increased insulin secretion. Similar insulin secretion thus occurred at very different cellular glutamate levels. Glutamine did not affect islet [Ca(2+)](i) and pH(i), whereas glucose and BCH slightly raised pH(i) and either slightly decreased (30 mm KCl) or increased (tolbutamide) [Ca(2+)](i). The general dissociation between changes in islet glutamate and insulin secretion refutes a role of beta-cell glutamate in the amplification of insulin secretion by glucose.     

The rise in concentration of free Ca2+ and of pH provides sequential, synergistic signals for secretion in antigen-stimulated rat basophilic leukemia (RBL-2H3) cells

Ag stimulation of rat basophilic leukemia (RBL-2H3) cells results in hydrolysis of inositol phospholipids, a transient increase in concentration of cytosol Ca2+ [( Ca2+]i), a gradual increase in cytosolic pH (pHi) and the activation of protein kinase C. To determine whether all these changes serve as signals for secretion, studies were conducted with cells permeabilized with streptolysin O in which pHi and [Ca2+]i could be varied independently of each other and enzyme activities could be manipulated. At resting pHi (approximately 7.0) and [Ca2+]i (0.1 microM), the permeabilized cells showed little secretory response to Ag. At resting pHi, elevated levels of Ca2+ (0.33 microM) were required for maximal secretory response to Ag. At a pHi of 7.4, however, 0.1 microM [Ca2+]i was sufficient to sustain near maximal responses to Ag. Therefore, a small increase of [Ca2+]i to 0.33 microM was required to initiate secretion, but once the pHi was elevated secretion could be sustained at near basal levels of [Ca2+]i. Since elevating the [Ca2+]i and pHi, by themselves promoted little secretion, another potentiating signal must have been generated by antigen stimulation. This signal was possibly transduced via hydrolysis of inositol phospholipids and protein kinase C. Even with an elevated [Ca2+]i (0.33 microM) the hydrolysis of the phospholipids and secretion stimulated by Ag were inhibited by guanosine 5'(2-O-thio)diphosphate and neomycin. Furthermore, both protein-kinase C and the secretory response to Ag were lost after permeabilized cells were washed but both were retained if cells were exposed to PMA before permeabilization.     

GPCR kinase 2 interacting protein 1 (GIT1) regulates osteoclast function and bone mass

G‐protein‐coupled receptor (GPCR) kinase 2 interacting protein‐1 (GIT1) is a scaffold protein expressed in various cell types including neurons, endothelial, and vascular smooth muscle cells. The GIT1 knockout (KO) mouse has a pulmonary phenotype due to impaired endothelial function. Because GIT1 is tyrosine phosphorylated by Src kinase, we anticipated that GIT1 KO should have a bone phenotype similar to Src KO. Microcomputed tomography of the long bones revealed that GIT1 KO mice have a 2.3‐fold increase in bone mass compared to wild‐type controls. Histomorphometry showed increased trabecular number and connectivity suggesting impaired bone remodeling. Immunoblot analysis of GIT1 expression showed that it was expressed in both osteoclasts and osteoblasts. Osteoblast activity and function assayed by alkaline phosphatase, mineral nodule formation, and in vivo calcein labeling were normal in GIT1 KO mice suggesting that the observed increase in bone mass was due to an osteoclast defect. GIT1 KO bone marrow cells differentiated into multinucleated osteoclasts, but had defective bone resorbing function on dentin slices. This defect was likely caused by loss of podosome belt based on immunofluorescence analysis and previous studies showing that GIT1 is required for podosome formation. Furthermore, we found that GIT1 was a regulator of receptor activator of NFκB (RANK) signaling since it was tyrosine phosphorylated in a Src‐dependent manner and was required for phospholipase C‐γ2 phosphorylation. These data show that GIT1 is a key regulator of bone mass in vivo by regulating osteoclast function and suggest GIT1 as a potential target for osteoporosis therapy. J. Cell. Physiol. 225: 777–785, 2010. © 2010 Wiley‐Liss, Inc.     

Central regulation of gastric acetylcholine metabolism and acid output: Analysis using stress and 2-deoxy-d-glucose administration in rats

The stress of immobilization in water caused a significant increase in the activity of choline acetyltransferase (CAT) and acetylcholinesterase (AChE), acetylcholine (ACh) content in the stomach and gastric acid secretion, but a decrease of choline content in rats. The increase in CAT activity began 1 h after the application of stress, peaked in 3 h and gradually decreased to normal within 7 h. Similar alterations in gastric acid secretion were observed. The ACh content in stomach tissue increased 30 min after the application of stress and remained elevated for 2.5 h. The content decreased to control levels after 5 h, and significantly increased again after 7 h. The choline content in stomach tissue significantly decreased 1 and 2 h after stress but returned to normal 3 h after the application. An increase in AChE activity was observed 2 and 7 h after the application of stress but normal levels were found after 4 h. Increases in CAT activity and acid output were also observed following administration of 2-deoxy-d-glucose (2-DG), but no changes in ACh and choline contents or AChE activity were observed. The increases in CAT activity and the acid secretion caused by stress and 2-DG administration were blocked by administration of hexamethonium. These results suggest that increases in gastric CAT, AChE activities and ACh content and a decrease of choline content in the early stages are results of increased vagus nerve activity, which influences gastric acid secretion. Furthermore, they suggest that alterations in ACh content and AChE activity at a later stage are less directly related to the increase in vagus nerve activity.