Stomach Wall Of Rats Research Articles

Safety assessment and gastrointestinal retention of orally administered cerium oxide nanoparticles in rats

Cerium oxide nanoparticles (CeO2 NPs, NM-212) are well-known for their catalytic properties and antioxidant potential, and have many applications in various industries, drug delivery, and cosmetic formulations. CeO2 NPs exhibit strong antimicrobial activity and can be used to efficiently remove pathogens from different environments. However, knowledge of the toxicological evaluation of CeO2 NPs is too limited to support their safe use. In this study, CeO2 NPs were orally administered to Sprague Dawley rats for 13 weeks at the doses of 0, 10, 100, and 1000 mg/kg bw/day, followed by a four week recovery period. The hematology values for the absolute and relative reticulocyte counts in male rats treated with 1000 mg/kg bw/day CeO2 NPs were lower than those in control rats. The clinical chemistry values for sodium and chloride in the treated male rat groups (100 and 1000 mg/kg/day) and total protein and calcium in the treated female rat groups (100 mg/kg/day) were higher than those in the control groups. However, these changes were not consistent in both sexes, and no abnormalities were found in the corresponding pathological findings. The results showed no adverse effects on any of the parameters assessed. CeO2 NPs accumulated in the jejunum, colon, and stomach wall of rats administered 1000 mg/kg CeO2 NPs for 90 days. However, these changes were not abnormal in the corresponding histopathological and immunohistochemical examinations. Therefore, 1000 mg/kg bw/day may be considered the “no observed adverse effect level” of CeO2 NPs (NM-212) in male and female SD rats under the present experimental conditions.

HISTOLOGICAL AND MORPHOLOGICAL CHANGES IN THE LYMPHOID STRUCTURES OF THE GASTRIC MUCOUS MEMBRANE IN WHITE RATS WITH THE ADMINISTRATION OF SODIUM GLUTAMATE.

The aim: To determine the histological and morphological changes of the lymphoid structures of the stomach in male rats under the influence of oral sodium glutamate at the rate of 15 mg/kg of body weight. Materials and methods: The scientific experiment was performed on 20 white non-linear male rats of reproductive age (4-5 months). The experimental animals were divided into two groups (10 rats in each group), which were orally received monosodium glutamate at a dose of 15 mg/kg body weight every day. We studied the effect of 2 and 4 weekly administration of monosodium glutamate at a dose of 15 mg/kg body weight, respectively, in the I and II groups of experimental animals (depending on the week of their decapitation). Rats of the control groups (n=10) were injected with a placebo for 2 and 4 weeks, namely 0.5 ml of dechlorinated tap water at room temperature. Intact control animals were also divided into two groups, 5 rats each, depending on the week of decapitation: respectively, III group - decapitation on the 2nd week of the experiment; IV group - decapitation on the 4th week of the experiment. After the experiments were completed, animals were decapitated under light ether anesthesia. According to the purpose of the study, pieces of rat stomach measuring 1.0 x 1.0 cm were taken from the front wall of the bottom of the stomach near the great curvature, cardiac and portal parts of the organ. Histological preparations were examined using a MICROmed SEO SСAN light microscope and a Vision CCD Camera. Morphometric studies were carried out according to the method of S. B. Stefanov, using grids No. 3/16. For electron microscopic examination, pieces of the stomach wall of rats were fixed in a 2.5% solution of glutaraldehyde in a 0.1 M phosphate buffer (pH 7.2-7.4) with subsequent fixation in a 2.0% solution of osmium tetroxide. After dehydration in alcohols and acetone, the material was embedded in eponaraldite. Sections were made on an LKB-8800-III ultramicrotome and studied using a JEM - 100-V microscope. To study the structural components of the lymphoid formations of the mucous membrane of different parts of the stomach of rats, semi-thin sections were made for the purpose of sharpening the blocks, which were stained with methylene blue. Results: The analysis of the obtained data of the conducted experiment indicates that the administration of monosodium glutamate in a dose of 15 mg/kg of body weight to rats already after 14 days leads to an increase in the density and size of the lymphoid structures of the GMM. The number of immunocompetent cells between the fundus of the gastric glands and the muscle plate increases in the diffuse lymphoid tissue of the gastrointestinal tract of rats in all its parts, both in the I and II groups of experimental animals. These changes are most pronounced in the cardiac and portal parts of the stomach. In both groups of experimental animals, the migration of interepithelial lymphocytes, macrophages, plasma cells, and tissue basophils to the surface epithelium increases. In both groups of experimental animals (and the II group of rats), lymphoid nodules and lymphoid pre-nodules of the gastric mucous membrane (GMM) are located between the bottom of the gastric glands and the muscular plate of the GMM. A gradual increase of medium lymphocytes in the GMM was established both in animals of I and II groups, while large lymphocytes increased in almost the same amount in experimental animals of both groups. Similar changes occur in the characteristics of the number of plasma cells, macrophages and tissue basophils in the lymphoid pre-nodules of GMM. Conclusions: Administering monosodium glutamate to rats at a dose of 15 mg/kg of body weight for 2 weeks leads to an increase in the density and size of lymphoid structures of the mucous membrane in all parts of the stomach with a predominant increase in the number of immunocompetent cells between the bottom of the gastric glands and the muscle plate. At the same time, more pronounced changes were found in the number of small lymphocytes, which tend to decrease by the 2nd week of the experiment, and vice versa - their density increases by the 4th week of monosodium glutamate administration.

Effect of Trianthema triquetra Rottl. ex Willed (Aizoaceae) on ethanol-induced gastric ulcers in experimental rats

Trianthema triquetra Rottl. Ex.Willed (T. triquetra) is a medicinal plant that belongs to the family Aizoaceae. The plant has been used traditionally as fodder, as a remedy for chronic ulcer, fever, and healing wounds. Therefore, the present study was intended to investigate the anti-ulcer ability of different fractions of T. triquetra to verify its folklore use in ulcer cure. Acute oral toxicity of all the fractions of T. triquetra was evaluated at a dose of 2g/kg b.wt. Anti-ulcer potential of nbutanol (TTB), chloroform (TTC), ethyl acetate (TTEA) and aqueous (TTA) fraction of crude methanolic extract of T. triquetra was assessed by using ethanol- induced gastric ulcer model in rats. Omeprazole at a dose of 20 mg/kg b.wt. was used as standard drug. After 1 hour of administration of all the fractions of T. triquetra, at a dosage of 300mg/kg b.wt., the gastric ulcer was induced in all animals by administering absolute ethanol (1mL/animal) orally except normal control group. After an hour, all the rats were sacrificed. Ulcer index, % age of ulcer inhibition, gastric pH, gastric volume, total acidity, gastric wall protein, gastric wall mucus and histopathology of the stomach wall of rats were assessed. All fractions of T. triquetra showed a substantial decrease in ulcer index and improvement in percentage inhibition compared to the disease control group. There was a rise in the amount of gastric wall mucus content, total protein content, gastric pH and a decrease in gastric volume and total acidity. Histopathological studies showed severe mucosal injury, leucocyte infiltration and edema in the disease control group compared to omeprazole and plant fractions treated animal groups. The present work encourages the conventional use of T. triquetra in the cure of ulcers.

Distinct Expression of Phenotypic Markers in Placodes- and Neural Crest-Derived Afferent Neurons Innervating the Rat Stomach.

Visceral pain is initiated by activation of primary afferent neurons among which the capsaicin-sensitive (TRPV1-positive) neurons play an important role. The stomach is a common source of visceral pain. Similar to other organs, the stomach receives dual spinal and vagal afferent innervation. Developmentally, spinal dorsal root ganglia (DRG) and vagal jugular neurons originate from embryonic neural crest and vagal nodose neurons originate from placodes. In thoracic organs the neural crest- and placodes-derived TRPV1-positive neurons have distinct phenotypes differing in activation profile, neurotrophic regulation and reflex responses. It is unknown to whether such distinction exists in the stomach. We hypothesized that gastric neural crest- and placodes-derived TRPV1-positive neurons express phenotypic markers indicative of placodes and neural crest phenotypes. Gastric DRG and vagal neurons were retrogradely traced by DiI injected into the rat stomach wall. Single-cell RT-PCR was performed on traced gastric neurons. Retrograde tracing demonstrated that vagal gastric neurons locate exclusively into the nodose portion of the rat jugular/petrosal/nodose complex. Gastric DRG TRPV1-positive neurons preferentially expressed markers PPT-A, TrkA and GFRα3 typical for neural crest-derived TRPV1-positive visceral neurons. In contrast, gastric nodose TRPV1-positive neurons preferentially expressed markers P2X2 and TrkB typical for placodes-derived TRPV1-positive visceral neurons. Differential expression of neural crest and placodes markers was less pronounced in TRPV1-negative DRG and nodose populations. There are phenotypic distinctions between the neural crest-derived DRG and placodes-derived vagal nodose TRPV1-positive neurons innervating the rat stomach that are similar to those described in thoracic organs.

The Effects of Moderate Exercise on Ethanol-Induced Gastric Injuries in Rats

Background: The role of oxygen-derived free radicals in the development of pathogenesis in acute gastric lesions induced by ethanol is well known. The beneficial effects of physical training on the antioxidant defenses of numerous tissues have been proved. Objectives: The present study was designed to evaluate the effects of exercise training on ethanol-induced gastric mucosal injuries in rats. Materials and Methods: In this experimental study, 28 Sprague-Dawley male rats were divided into 4 equal groups: sedentary control, exercise control, sedentary plus ethanol and exercise plus ethanol groups. The rats were subjected to moderate treadmill exercise protocol for 30 consecutive days (one hour per day). Thereafter, ethanol-treated groups received absolute ethanol (1 mL/rat) by gavage to induce gastric ulcer. Antioxidant status and lipid peroxidation of stomach wall were measured by evaluation of glutathione peroxidase (GPx), catalase activities (CAT) and thiobarbituric acid reactive substances (TBARS) concentration, respectively. Results: The histopathological findings of this study showed that moderate exercise training significantly inhibited the ethanol-induced gastric lesions in rats. Biochemical results also showed that administration of ethanol significantly decreased GPx activity and increased TBARS when compared to the sedentary control group (P < 0.05). In contrast, the exercise plus ethanol group showed higher GPx activity and lower TBARS concentration when compared to the ethanol-treated rats (P < 0.05). The catalase activity in ethanol-treated rats tended to be decreased when compared to control group. Conclusions: It seems that the preventive effects of exercise training may be mediated through increasing GPx activity subsequently inhibition of lipid peroxidation in stomach wall of rats.

Effect of intestinal inflammation on neuronal survival and function in the dorsal motor nucleus of the vagus

The effects of intestinal inflammation on the central nervous system are unknown. The dorsal motor nucleus of the vagus (DMNV) integrates peripheral and central signals and sends efferent signals to the gastrointestinal system. The purpose of this study was to determine the effects of intestinal inflammation on the DMNV in an animal model and in vitro. Carbocyanine dye (DiI) was injected into the stomach wall of rats to label retrogradely the neurons of the DMNV. Colitis was induced with trinitrobenzene sulfonic acid (TNBS). Tissue was examined under fluorescent microscopy. In vitro studies were performed using primary culture of DMNV neurons. Cell proliferation was measured by BrdU incorporation. Apoptosis was measured by an enzyme sandwich-linked immunosorbent assay. Single-cell cytoplasmic calcium transients were determined using the fluorescence dye fura-2-AM. Reverse transcriptase-polymerase chain reaction of glutamate receptor was performed. Animals treated with TNBS ate less and lost weight compared with controls. Microscopic analysis demonstrated a 77% decrease in DiI labeling in the DMNV of TNBS animals compared with controls. Cell proliferation in DMNV neurons after 24-hour exposure to the cytokines interleukin- (IL)-1 beta, IL-6, or tumor necrosis factor- (TNF)-alpha was significantly decreased. Similarly, apoptosis of DMNV neurons after 24 hours of incubation with IL-1 beta or TNF-alpha was significantly increased, but no changes resulted with IL-6. Exposure to each cytokine resulted in decreased glutamate-induced intracellular calcium transients. Transcription of glutamate receptor was decreased after 24-hour exposure to TNF-alpha. DMNV neurons projecting to the stomach are reduced in number after induction of colitis in rats. In vitro, proinflammatory cytokines diminish DMNV cellular proliferation, increase apoptosis, and alter calcium responses to glutamate. These results indicate that intestinal inflammation affects adversely neuronal survival and function in the DMNV.

Effects of ghrelin on neuronal survival in cells derived from dorsal motor nucleus of the vagus

The effects of intestinal inflammation on the central neurons projecting to the enteric nervous system are unknown. The dorsal motor nucleus of the vagus signals to the gastrointestinal system. Ghrelin is elevated in patients with inflammatory bowel disease and has been implicated as an inflammatory mediator. The purpose of this study was to investigate the effects of gastrointestinal inflammation on the dorsal motor nucleus of the vagus in rats, as well as the effects of proinflammatory cytokines and ghrelin on neurons from the dorsal motor nucleus of the vagus in vitro. DiI was injected into the stomach wall of rats to retrogradely label neurons of the dorsal motor nucleus of the vagus. Intestinal inflammation was induced with indomethacin injection. Serial serum ghrelin measurements were performed. Tissue was examined under fluorescent microscopy. In vitro studies using primary culture of neurons from the dorsal motor nucleus of the vagus were performed. Reverse transcriptase-polymerase chain reaction for cytokine transcripts and immunohistochemistry for cytokine receptors were performed. Cell proliferation and apoptosis were measured by enzyme-linked immunosorbent assay. A significant decrease of DiI labeling was demonstrated in the dorsal motor nucleus of the vagus of animals injected with indomethacin. Serum levels of ghrelin were significantly elevated 2 days after induction of inflammation. In vitro, apoptosis and cell proliferation were measured after 24-hour exposure to experimental conditions. Ghrelin alone had no effect on apoptosis. Exposure to interleukin (IL)-1 beta or tumor necrosis factor (TNF)-alpha increased apoptosis. The addition of ghrelin to cytokine resulted in significant decreases in apoptosis compared to cytokine alone. Ghrelin significantly increased neuronal proliferation. Exposure to IL-1 beta, IL-6, or TNF-alpha significantly decreased proliferation. The addition of ghrelin to TNF-alpha or IL-6 significantly increased cellular proliferation compared to cytokine alone. Neurons from the dorsal motor nucleus of the vagus that project to the stomach are reduced in number after induction of colitis in rats. In vitro, proinflammatory cytokines increase apoptosis and decrease cell proliferation of neurons from the dorsal motor nucleus of the vagus. These effects are attenuated by ghrelin.

Role of bradykinin in gastric vasodilation caused by hypertonic saline and acid back diffusion

Protective vasodilation in response to tissue injury and acid back diffusion is associated with release of bradykinin in the rat stomach. We hypothesized that bradykinin might be involved in mechanisms behind such vasodilation via influence on mast cells and sensory neurons. Acid back diffusion after mucosal barrier disruption with hypertonic saline evoked degranulation of mast cells in the rat stomach wall. Acid back diffusion was also associated with increased luminal release of histamine and gastric blood flow in normal rats, but not in mast cell-deficient rats. Bradykinin (BK 2) receptor blockade inhibited degranulation of submucosal mast cells in the stomach and attenuated gastric vasodilation both in response to acid back diffusion and after stimulation of sensory neurons with capsaicin. Gastric vasodilation caused by mucosal injury with hypertonic saline alone was associated with degranulation of mucosal mast cells. These events were unaffected by inhibition of prostaglandin synthesis, whereas bradykinin (BK 2) receptor blockade was associated with abolished vasodilation and inhibition of mucosal mast cell degranulation. We conclude that bradykinin is involved in gastric vasodilation caused by hypertonic injury alone via influence on mast cells, and by acid back diffusion via influence on both sensory neurons and mast cells.

Hemorrhagic shock activates mast cells in the rat stomach wall.

The activation of mast cells (MC) and liberation of their mediators can play an essential role in initiating and controlling inflammatory processes in the wall of the gastrointestinal tract (GIT) due to ischemia. The role of MC in changes induced by hemorrhagic shock (HS) remains unknown. Heparin provided by MC seems to inhibit local inflammation and prevent DIC. The aim of this study was to evaluate the morphometric changes and biochemical activity of MC in the stomach wall after 75 minutes of hemorrhagic shock. The MC in mucosal, submucosal, muscular and serosal compartments of the various stomach wall regions were examined in shocked rats and in the control group. Additionally, the contents of glycosaminoglycans (GAG), measured as uronic acids concentration, as well as anticoagulative activity in the stomach wall were assessed. HS resulted in an evident increase in the number of mast cells detected in the stomach mucosa and serosa, in slight alterations in number of MC in the submucosal and muscular layers, a significant increase in size and changes of the shape of the MC. The elevation of the width, area, and circular shape of MC in all layers were noted. No clear and significant differences between various stomach regions in MC numbers and MC sizes could be shown. No reaction of other inflammatory cells at this stage of shock was observed. Highly significant increases in GAG concentration, and anticoagulative activity in the stomach wall due to shock were noted. The morphometric and biochemical data may indicate MC activation, especially in mucosa and serosa. The shock-induced migration of MC settled in the stomach wall seems to be possible. The results suggest an essential role of MC reaction in the stomach wall in the early phase of hemorrhagic shock.

Distribution of nitric oxide synthase in stomach wall in rats.

It has been shown that neuronal nicotinamide adenene dinucleotide phosphate-diaphorase (NADPH-d) may correspond to the neuronal nitric oxide synthase (NOS), and may be used as a marker for NOS in the central and peripheral nervous system. Thus, NADPH-d histochemistry provides us with a mean to specifically identify neurons producing nitric oxide (NO)[1,2]. Recent pharmacological and physiological-stu-dies demonstrated that NO is a neurotransmitter in the non-adrenergic non-cholinergic (NANC) in-hibitory nerves in the mammalian gastrointestinal tract. It may play a very important role in then euronal regulation of gut. NOS activity is present in neurons and fibers of the major enteric nerve layer in intestine[3]. However, there have been far fewer studies of NOS activity in stomach wall. If NO is a transmitter of NANC in hibitory nerves, it should be present in neurons innervating the muscularis. What proportion of nerves produce NO? What is the pattern of innervation of these neurons? To answer these questions, we examined the distribution and morphological feature of NOS positive neurons in the stomach wall with improved whole mount preparation technique.

Availability of arachidonic acid in major phospholipids of mucosa and the stomach wall of rats.

The purpose of this study was to examine the availability of arachidonic acid in phosphatdidylcholine (PC) and phosphatidylethanolamine (PE) of mucosa and the stomach wall of adult male Wistar rats fed a standard diet. There were significant differences in the fatty acid composition of PC and PE between various parts of the stomach. The mucosa had the lowest level of arachidonic acid (20:4n-6) in PC, followed by the corresponding stomach wall or glandular part, whereas the forestomach or the upper part had the highest level of 20:4n-6. The level of 20:4n-6 in PE was identical in gastric mucosa and the stomach wall of both the lower and upper parts. The levels of 18:1n-9 and 18:2n-6 were significantly higher in both PC and PE of mucosa than in the stomach wall. The levels of 16:0 and 18:0 in PC were lower in mucosa than in either forestomach or the glandular part. In mucosal PE, the levels of 18:0 and 22:6n-3 were lower than in forestomach and glandular part. The glandular part had significantly higher level of 16:0 and lower level of 20:4n-6 in PC compared to the forestomach. The arachidonic acid level of PC was significantly different in various parts of the rat stomach, with the lowest level in mucosa, whereas the level of 20:4n-6 in PE was identical in mucosa and stomach wall. These phospholipids had higher levels of saturated fatty acids in the stomach wall than in gastric mucosa.

Studies on the Metabolic Fate of HSR-803. (I). The Absorption, Distribution and Excretion in Rats and Dogs after Single Administration.

The absorption, distribution and excretion of N-[p-[2-(Dimethylamino)-ethoxy]benzyl]veratramide hydrochloride (HSR-803) were investigated in rats and dogs following single administration of 14C-labelled compound. 1. Blood and serum radioactivity reached the Cmax at 0.5 to 1 hr after single oral administration of 14C-HSR-803 to rats and dogs, and then declined with half-lives of 3.42, 10.30 hr for whole blood and 3.78, 10.12 hr for serum, respectively. The site of absorption in rats was the entire intestine, particularly the duodenum. 2. Radioactivity level was high in tissues such as the small intestine, stomach, kidney and liver of rats after oral administration of 14C-HSR-803. In the central nervous system, the concentration was low. Elimination from each tissue was rapid. Radioactivity in the stomach wall in rats was high after intravenous administration of 14C-HSR-803. 3. When 14C-HSR-803 was administered orally, urinary and fecal excretions were 63.6 and 35.7% of the dose for rats, and 46.7 and 50.9% of the dose for dogs, as determined within 168 hrs. In rats and dogs, 68.1 and 79.3% of the dose were excreted into bile after oral dosing, respectively. In rats, enterohepatic circulation was observed. 4. In vitro protein binding to human, rat and dog serum was 95.5, 79.6 and 57.5% at the concentration range of 0.2-10.0 μg/ml, respectively.

Transfer of exogenous macromolecules from rat stomach wall to blood and lymph is dependent on molecular weight.

Transfer selectivity to the blood and the lymph of exogenous dextrans of various average molecular weight (approximate 4, 10, 18, 39 and 70 kilodaltons (kDa)) after dosing to the subserosal layer of the rat stomach wall was investigated by measuring the fluorescein isothiocyanate labelled dextran concentrations in the lymph of the thoracic duct and the peripheral plasma. The lymph/plasma level ratio of the dextrans rose greatly with the increase in molecular weight (over 10kDa) owing largely to the lower plasma concentration, although the lymph levels of small dextran (4kDa) were not significantly higher than the plasma levels. These results indicate that there is an inverse relation between plasma levels of dextrans and their molecular weight, and also suggest that the molecular weight threshold of transfer selectivity of dextran to the blood and the lymph administered in the rat stomach wall is between 4-10 kDa.

Effect of serotonin on the immunoreactive thyrotropin-releasing hormone concentrations of the rat stomach.

The effects of serotonin and its related compounds on immunoreactive thyrotropin-releasing hormone (ir-TRH) concentrations of the rat stomach wall and gastric juice were studied. Either serotonin, cyproheptadine or GR38032F was injected intraperitoneally, and the rats were decapitated at various times after the injection. ir-TRH concentrations of the stomach wall and gastric juice were measured by radioimmunoassay, and gastric serotonin concentrations were measured by HPLC. ir-TRH concentrations of the stomach wall decreased, and ir-TRH concentrations of gastric juice increased significantly after serotonin injection. On the other hand, both cyproheptadine and GR38032F did not affect ir-TRH concentrations of the stomach. The effects of serotonin on ir-TRH concentrations of the stomach were significantly blocked by the pretreatment of cyproheptadine and GR38032F. The reciprocal changes of gastric ir-TRH and serotonin concentrations were observed without changes in gastric juice pH. These findings suggest that serotonin stimulates ir-TRH release from the stomach wall into gastric juice, and the effects of serotonin on ir-TRH release may be partly mediated via 5-HT2- and 5-HT3-receptors.

Metabolism of enkephalin in stomach wall of rats

Peptidases degrade neuropeptides and thereby limit the duration and extent of their influence. This investigation examined the importance of peptidases in the degradation of the neuropeptide enkephalin in the stomach wall of the rat. Metabolism of [Leu5]- and [D-Ala2][Leu5]enkephalin by gastric membranes was examined in vitro. Degradation of [Tyr1-3H][Leu5]enkephalin was studied in the gastric submucosa of anesthetized and conscious rats in vivo by using a catheter to deliver peptide to tissues and implanted dialysis fibers to collect the metabolites. Specific inhibitors were used to assess the contribution of particular enzymes. [Leu5]- and [Tyr1-3H][Leu5]enkephalin were metabolized by membranes and in the stomach wall by hydrolysis of the Tyr1-Gly2 bond. Degradation was inhibited by the aminopeptidase inhibitor amastatin (10(-5) M in vitro, 10 nmol in vivo). Inhibitors of endopeptidase-24.11 (phosphoramidon) and angiotensin-converting enzyme (captopril) did not inhibit degradation. Metabolism of the aminopeptidase-resistant analogue [D-Ala2][Leu5]enkephalin by membranes was unaffected by amastatin and weakly inhibited by phosphoramidon affected by amastatin and weakly inhibited by phosphoramidon and captopril. A carboxypeptidase removed the COOH-terminal leucine residue and made a substantial contribution to degradation of both peptides by gastric membranes.

Phospholipase A 2 activity of rat stomach

Phospholipase A activity in rat stomach wall and in gastric content was studied using [1- 14C]dioleoylphosphatidylcholine as substrate. The optimum activity of the stomach wall was found to take place at pH 7.O. During optimal phospholipase action about 40% of the [1- 14C]oleic acid released was due to an active intracellular lysophospholipase. The gastric phospholipase required 5 m m Ca 2+ for full activity and is inhibited by EDTA. It specifically hydrolyzed the sn-2 position of the phospholipid molecule. The enzyme was heat labile and inactivated by acidification at pH 3.0. The gastric content enzyme had a lower specific activity and an optimum pH of 8.0. It was heat stable and was not inactivated by acidification. These results indicate that gastric content phospholipase A is of pancreatic origin, via a duodenal reflux. By ligating the stomach we were able to further confirm that the gastric wall phospholipase was different from that of the gastric content. It originated from the stomach mucosa. Subcellular fractionation suggests that the gastric phospholipase A 2 is essentially bound to the plasma membrane. About 6% of the activity was found to be soluble. Biopsies of human gastric mucosa displayed a phospholipase A activity which had similar properties to that of rat gastric enzyme. The physiological function of this enzyme is discussed in terms of prostaglandin synthesis via the release of arachidonic acid.

Catabolism of substance P and neurotensin in the rat stomach wall is susceptible to inhibitors of angiotensin converting enzyme

The purpose of this investigation was to examine the pathway of substance P (SP) and neurotensin (NT) catabolism in the gastric wall of the rat and identify some of the enzymes involved. Under anaesthesia an infusion catheter and a bundle of dialysis fibres were implanted into the stomach wall of the rat. Experiments commenced on conscious rats 2 days after surgery. In control experiments [ 3H]-SP(Pro-2,4) or [ 3H]-NT(Tyr-3,11) were injected into gastric tissues through the catheter and catabolites were collected in the dialysis fibres and separated by high pressure liquid chromatography. In other studies captopril, MK422 (inhibitors of angiotensin converting enzyme) or phosphoramidon (an inhibitor of endopeptidase-24.11, ‘enkephalinase’) were injected into gastric tissues before the peptide label. SP1–11 was degraded to mainly SP1–2, SP3–4 with some SP1–6, SP1–7 and SP1–8. Catabolism was partially but significantly (5% level) inhibited by MK422 and captopril, but not by phosphoramidon. NT1–13 was degraded to NT1–8, NT9–13, NT1–11 and NT1–12. NT catabolism was partially but significantly (5% level) inhibited by MK422. It is concluded that an enzyme resembling angiotensin converting enzyme is involved in the initial stages of SP and NT catabolism in the rat stomach. The involvement of other peptidases cannot be excluded because inhibition of breakdown was not complete.

Peptide-containing nerve fibers in the stomach wall of rat and mouse

Peptide-containing nerve fibers were found to be numerous in the glandular stomach of the rat and mouse. The immunoreactive neuropeptides demonstrated included vasoactive intestinal polypeptide (VIP), peptide histidine isoleucine (PHI), gastrin-releasing peptide (GRP), substance P (SP), enkephalin, somatostatin, cholecystokinin, and neuropeptide Y (NPY). The density and distribution of the various peptide-containing fibers did not differ overtly between the pyloric and oxyntic gland areas except for the GRP fibers, which were fewer in the pyloric than in the oxyntic mucosa. The entire VIP nerve fiber population was found to also contain PHI. Immunoreactive NPY was found to occur in the VIP/PHI fibers (VIP/PHI/NPY fibers) in the smooth muscle and intramural ganglia of both rat and mouse and in the mucosa of the mouse. Mucosal VIP/PHI fibers in the rat did not contain any NPY-like material. Perivascular NPY fibers in both species and mucosal NPY fibers in the rat did not contain VIP or PHI. The mucosa harbored numerous GRP fibers and VIP/PHI (rat) or VIP/PHI/NPY (mouse) fibers, and a modest number of NPY (rat) and SP fibers. In the submucosa the peptide-containing nerve fibers were found mainly in the ganglia and around blood vessels. Blood vessels received a rich supply of NPY fibers; the number of perivascular VIP/PHI, GRP, and SP fibers was much lower by comparison. The smooth muscle and myenteric ganglia harbored not only VIP/PHI/NPY, GRP, and SP fibers but also enkephalin, somatostatin, and cholecystokinin fibers. Gastrin-releasing peptide, VIP/PHI/NPY, SP, and enkephalin nerve cell bodies occurred in the myenteric ganglia. As studied in the rat, vagal denervation did not affect the density and distribution of the various peptide-containing nerve fibers. After sympathectomy, mucosal and perivascular NPY fibers disappeared. The other types of peptide-containing nerve fibers were not affected.

PHARMACOKINETICS OF FENTANYL AS A POSSIBLE EXPLANATION FOR RECURRENCE OF RESPIRATORY DEPRESSION

The pharmacokinetics of fentanyl are complicated by an additional increase in plasma concentration during the elimination phase of the drug. We have confirmed that fentanyl is excreted in the gastric juice and reabsorbed from the alkaline medium of the small intestine. In addition, the stomach wall in rats has an important storage capacity for fentanyl. A maximum of about 20% of the dose was found in the stomach wall after i.v. injection. In man the resected part of the stomach contained 16% of the dose, 10 min after injection. These observations could be important in explaining the occurrence of respiratory depression in the period after operation.

Effects of stress and drugs on the catecholamine and pepsin concentrations in stomach wall of rat.

Reserpine, serotonin, and histamine as well as stress were employed to produced dystrophic lesions in the gastric mucosa of rats. Analysis of stomach tissues revealed that agencies which reduced catecholamine concentration also decreased endogenous levels of pepsinogen. Concentrations of the zymogen were increased after parenteral administration of dopa, but were not changed by injections of alpha-methyl-dopa. The evidence supports the suggestion that catecholamines participate in the control of pepsin production and are involved in the secretory function of the stomach.