Gastrointestinal Tract Of Cats Research Articles

Effects of inulin on fecal microbiota and specific immunity in cats

Inulin has potential benefits for alleviating intestinal stress syndrome, constipation, and immunomodulation. However, its effects on cat gastrointestinal tract remain unexplored. Eight healthy adult British short-haired cat were administered 50 mg/kg/d inulin with a basal diet for 21 days, while fecal samples were collected to measure indole and 3-methylindole levels, immune index detection, and fecal microbial diversity on days 0, 7, 14, and 21. The results showed that adding inulin to the diet of cat could cause the increase of sIgA on day 14 (P < 0.05) and enhance their immune performance. In addition, it will also affect the fecal microbiota of the cat. Collinsella abundance was significantly increased, which could indulge ursodeoxycholic acid production. Feeding inulin had no significant effect on the levels of indole and 3-methylindole (P > 0.05). The above results showed that inulin supplementation in cat diet could improve cat health by enhancing immunity and increasing intestinal beneficial flora.

Fecal Concentrations of Long-Chain Fatty Acids, Sterols, and Unconjugated Bile Acids in Cats with Chronic Enteropathy.

Chronic enteropathy (CE) in cats encompasses food-responsive enteropathy, chronic inflammatory enteropathy (or inflammatory bowel disease), and low-grade intestinal T-cell lymphoma. While alterations in the gut metabolome have been extensively studied in humans and dogs with gastrointestinal disorders, little is known about the specific metabolic profile of cats with CE. As lipids take part in energy storage, inflammation, and cellular structure, investigating the lipid profile in cats with CE is crucial. This study aimed to measure fecal concentrations of various fatty acids, sterols, and bile acids. Fecal samples from 56 cats with CE and 77 healthy control cats were analyzed using gas chromatography-mass spectrometry, targeting 12 fatty acids, 10 sterols, and 5 unconjugated bile acids. Fecal concentrations of nine targeted fatty acids and animal-derived sterols were significantly increased in cats with CE. However, fecal concentrations of plant-derived sterols were significantly decreased in cats with CE. Additionally, an increased percentage of primary bile acids was observed in a subset of cats with CE. These findings suggest the presence of lipid maldigestion, malabsorption, and inflammation in the gastrointestinal tract of cats with CE. Understanding the lipid alterations in cats with CE can provide insights into the disease mechanisms and potential future therapeutic strategies.

An Update on Feline Calicivirus.

Feline Calicivirus (FCV) is one of the most common viral pathogens in domestic cats worldwide. The first report of FCV dates back to 1957, when FCV was isolated from the gastrointestinal tract of cats in New Zealand. Subsequent reports recognised FCV as a cause of respiratory disease in cats, and at present, feline practitioners worldwide are daily confronted with cats suffering from suspected FCV. The highly mutagenic nature of FCV and its high genetic plasticity enable the virus to successfully survive in the feline population, and pose a special challenge as regards the diagnosis, treatment, and prevention of FCV-induced disease. Upper respiratory tract disease has been considered a common clinical sign of FCV infection. A study from Switzerland demonstrated that oral ulcerations, salivation and gingivitis-stomatitis were more commonly associated with FCV infection than upper respiratory tract disease, and less than half of the cats suspected to have FCV infection were found to be FCV-positive. Furthermore, a study investigating FCV isolates from Switzerland found some evidence that the genetic background of cats might influence their susceptibility to FCV infection. This review article provides a comprehensive summary of the FCV literature, and integrates the results of recent research on FCV's genetic characteristics, the cellular and humoral immunity evoked by FCV vaccination and infection, the diagnosis of FCV, FCV prevention/vaccination, the risk factors associated with FCV, and the hygienic measures necessary in FCV-contaminated areas. After each section, the key points are summarised, and relevant information is outlined to help feline practitioners in FCV diagnosis, treatment and prevention.

Whole genome sequencing of a feline strain of Tritrichomonas foetus reveals massive genetic differences to bovine and porcine isolates

Tritrichomonas foetus is a protozoan parasite that colonizes the reproductive tract of cattle as well as the gastrointestinal tract of cats. Bovine tritrichomonosis is a sexually transmitted disease whereas feline tritrichomonosis is thought to be transmitted by the fecal-oral route. Furthermore, T. foetus is known as an essentially apathogenic commensal located in the nasal cavity of pigs. Transmission of T. foetus between the different hosts has to be considered a realistic scenario that may have important implications for the epidemiology of infections and disease. In our study, we generated whole genome sequencing (WGS) data from bovine, feline and porcine T. foetus strains to investigate the genetic (dis)similarities among these diverse strains. As a reference, we used a previously released draft assembly from a bovine T. foetus strain K isolated from an infected bull in Brazil. In particular, we identified single nucleotide polymorphisms (SNPs) and the insertion-deletion (indel) variations within the genomes of the different strains. Interestingly, only a low degree of polymorphism (68 SNPs and indels) was found between the bovine and the porcine strains in terms of variants with a predicted impact of moderate or high and where one species is homozygous for one allele and the other homozygous for the other allele. Conversely, however, a 964 times higher number of such differences was detected by comparing the feline with either the bovine (65,569) or the porcine (65,615) strain. These data clearly indicated a close phylogenetic relationship between bovine and porcine T. foetus but a remarkable genetic distinctness of these two strains from the feline strain. The latter observation was confirmed by PCR-based sequencing of 20 in silico-selected indel markers and five in silico-selected SNP markers that uniformly demonstrated a relatively distant phylogenetic relationship of three independent feline T. foetus isolates in comparison to the bovine and porcine strains investigated. In summary, our comparative genome sequencing approach provided further insights into the genetic diversity of T. foetus in relation to the different host origins of the parasite. Furthermore, our study identified a large number of SNP- and indel-containing sequences that may be useful molecular markers for future epidemiological studies aimed at the elucidation of the transmission patterns of T. foetus within different host species.

Localization of cannabinoid and cannabinoid related receptors in the cat gastrointestinal tract

A growing body of literature indicates that activation of cannabinoid receptors may exert beneficial effects on gastrointestinal inflammation and visceral hypersensitivity. The present study aimed to immunohistochemically investigate the distribution of the canonical cannabinoid receptors CB1 (CB1R) and CB2 (CB2R) and the putative cannabinoid receptors G protein-coupled receptor 55 (GPR55), nuclear peroxisome proliferator-activated receptor alpha (PPARα), transient receptor potential ankyrin 1 (TRPA1), and serotonin receptor 5-HT1a 5-HT1aR) in tissue samples of the gastrointestinal tract of the cat. CB1R-immunoreactivity (CB1R-IR) was observed in gastric epithelial cells, intestinal enteroendocrine cells (EECs) and goblet cells, lamina propria mast cells (MCs), and enteric neurons. CB2R-IR was expressed by EECs, enterocytes, and macrophages. GPR55-IR was expressed by EECs, macrophages, immunocytes, and MP neurons. PPARα-IR was expressed by immunocytes, smooth muscle cells, and enteroglial cells. TRPA1-IR was expressed by enteric neurons and intestinal goblet cells. 5-HT1a receptor-IR was expressed by gastrointestinal epithelial cells and gastric smooth muscle cells. Cannabinoid receptors showed a wide distribution in the feline gastrointestinal tract layers. Although not yet confirmed/supported by functional evidences, the present research might represent an anatomical substrate potentially useful to support, in feline species, the therapeutic use of cannabinoids during gastrointestinal inflammatory diseases.

Lymphocytic alimentary lymphoma in a feline: therapy with lomustine and prednisone - Case report

Among the hematopoietic neoplasms most observed in the feline species, lymphoma is mentioned. Being classified according to the anatomical site affected. The alimentary form is considered the second most common neoplasia found in the gastrointestinal tract of cats, which can affect the liver, spleen and pancreas. Older animals and/or retrovirus carriers have a bigger risk for the development of the disease. Clinical symptomatology varies according to the location, the age of the patient and the presence or absence of comorbidities. The treatment of the lymphocytic alimentary lymphoma aims to improve quality and increase the life span of patients. Thus, the importance of early diagnosis, through hematological, biochemical and imaging tests, as well as intestinal biopsy is highlighted. The follow-up of patients belonging to the risk group is also another essential factor for the recognition of the disease. The objective of this work is to report the case of a seven-year-old female feline with a history of hyporexia, prostration, emesis and progressive weight loss. After further examination, it was diagnosed a lymphocytic alimentary lymphoma and the treatment was with chemotherapy with lomustine and prednisone. The therapy demonstrated few side effects and an efficient response to disease control.

Case report: Anaerobiospirillum prosthetic joint infection in a heart transplant recipient

BackgroundWe report a case of prosthetic hip joint infection in a heart transplant recipient due to Anaerobiospirillum succiniciproducens, a genus of spiral-shaped curved anaerobic gram-negative rod which colonizes the gastrointestinal tract of cats and dogs. Invasive infections in humans are rare and typically occur in immunocompromised hosts.Case presentationA 65-year-old male dog breeder with a history of rheumatoid arthritis, bilateral hip arthroplasties, and non-ischemic cardiomyopathy with a heart transplant 10 years ago presented with a three month history of progressive left hip pain and frank purulence on hip aspiration. He underwent irrigation and debridement of the left hip and one-stage revision with hardware exchange. Although gram stain and culture from synovial fluid and intraoperative cultures were initially negative, anaerobic cultures from tissue specimens later grew a spiral-shaped gram-negative rod, identified as Anaerobiospirillum spp. by 16S rRNA gene sequencing. The patient was treated with ceftriaxone 2 g daily for 6 weeks with a good response to treatment. A similar organism was unable to be isolated from culture of 2 of the patient’s dogs, however, they were thought to be the most likely source of his infection.ConclusionAnaerobiospirillum spp. should be considered in immunocompromised patients with exposure to dogs or cats who present with bacteremia, gastrointestinal infection, pyomyositis, or prosthetic joint infections, especially in cases of culture-negative or with anaerobic culture growth.

0226 Dietary manipulation of canine and feline gut microbiome

Dogs and cats evolved as Carnivora and have traditionally relied on high-protein, high-fat diets containing relatively low fiber concentrations. Despite having a simple gastrointestinal tract designed to digest such diets, a rich microbial community exists. Today's pet dogs and cats live in close proximity to humans and have similar environmental exposures, serving as potential vectors for pathogen exposure. Dogs and cats are also afflicted by many of the complex diseases present in humans, including obesity, diabetes, inflammatory bowel diseases, and cancers, all of which may be influenced by diet and the gut microbiota. Given their proximity to humans, similar disease incidence and etiology, and unique metabolism, microbiome research in dogs and cats may not only lead to improved pet nutrition and veterinary care, but may increase our understanding of host-microbe interactions, with relevance to human metabolism and diseases and public health at large. Molecular techniques, including high-throughput sequencing, have dramatically changed the research landscape in regards to gastrointestinal microbiology. These techniques have been used to characterize the phylogeny and functional capacity of the canine and feline gastrointestinal microbiota and identify the effects of diet, age, and disease on these communities. Several hundred bacterial phylotypes, predominated by members of Firmicutes, Fusobacteria, Proteobacteria, Bacteroidetes, and Actinobacteria, are now known to inhabit the dog and cat gastrointestinal tract. Recent studies have revealed that the functional capacity of the gastrointestinal microbiota in dogs and cats is quite broad and similar to that of humans and rodent models. Although these populations are quite stable over time, our laboratory has demonstrated that macronutrient profile (e.g., dietary protein:carbohydrate ratio), dietary fiber amount and type, and the form of food consumed (e.g., raw vs. extruded diets) may have dramatic effects on the gastrointestinal microbiome of these host species. These dietary changes have not only been reported to impact microbial diversity and richness, gene content, and metabolic activity, but to alter host physiology and metabolism as well. Unfortunately, the majority of research has been performed in healthy animals housed in research colonies rather than free-living pets. Continued research on the composition and activity of the canine and feline gastrointestinal microbiomes, and how they are impacted by dietary intervention and other environmental exposures, is needed to increase our understanding of the host-microbe interactions that occur in the gastrointestinal health and their relevance to health and disease.

Characterization of the T-cell receptor gamma chain gene rearrangements as an adjunct tool in the diagnosis of T-cell lymphomas in the gastrointestinal tract of cats

Feline alimentary lymphoma is the most common hematopoietic neoplasia in cats. It affects mainly the small intestines and is most frequently of T-cell origin. Evaluation of a fine needle aspirate is often the first step in the diagnostic work-up. Differentiation between a resident mature lymphocyte population as encountered in inflammatory bowel disease and small cell lymphoma cannot be achieved by cytology alone. Even full thickness biopsies evaluated by histopathology can be inconclusive. These cases warrant the application of complementary tools like PCR-based T-cell receptor (TCR) clonality testing for confirmation.The aim of this study was to optimize the DNA extraction protocol for formalin fixed and paraffin embedded tissues (FFPE) and to establish a heteroduplex analysis to enhance resolution of the PCR fragments of the T-cell receptor gamma (TCRG) V-J gene. The new protocols resulted in improved quantity and quality of the extracted DNA. Heteroduplex analysis of the samples improved the resolution of the electrophoresis results so that rules for interpretation of the different patterns could be established. Application of this improved setup detected clonal rearrangements in at least one TCRG primer reaction in 31 of 36 of our feline intestinal lymphoma samples after DNA quality testing.

Urinary excretion of dietary Maillard reaction products in healthy adult female cats.

During processing of foods, the Maillard reaction occurs, resulting in the formation of advanced Maillard reaction products (MRP). Varying amounts of MRP have been found in commercially processed pet foods. Dietary MRP can be absorbed and contribute to the endogenous pool of MRP and possibly the etiology of age-related diseases. The aim of the present study was to determine urinary excretion of dietary MRP in cats fed commercial moist and dry foods. A pilot study with 10 cats, conducted to determine the adaptation time required for stable urinary excretion of MRP when changing to a diet with contrasting MRP content, showed an adaptation time of 1 d for all components. In the main study, 6 commercially processed dry and 6 moist diets were fed to 12 adult female cats in 2 parallel randomized, 36-d Latin square designs. The 24-h urine was collected quantitatively using modified litter boxes, and fructoselysine (FL), carboxymethyllysine (CML), and lysinoalanine (LAL) were analyzed using ultra high performance liquid chromatography (UHPLC) - mass spectrometer. Daily urinary excretion of FL and CML showed a positive relationship with daily intake in the dry ( = 0.03 and < 0.01, respectively) and moist ( < 0.01) foods. For LAL, no significant relationship was observed. Urinary recovery (% ingested) showed a negative relationship with daily intake for FL, CML, and LAL in the dry foods ( < 0.01, < 0.01, and = 0.08, respectively) and for CML and LAL in the moist foods ( < 0.01). The observed increase in urinary excretion with increasing dietary intake indicates that dietary MRP were absorbed from the gastrointestinal tract of cats and excreted in the urine. The adaptation time with change in diet indicates a likely effective excretion of MRP. Minimum apparent absorption of FL, CML, and LAL was found to range between 8% and 23%, 25% and 73%, and 6% and 19%, respectively. The observed decrease in urinary recovery suggests a limiting factor in digestion, absorption, metabolism, or urinary excretion. This study shows that dietary MRP in commercial diets are absorbed and excreted via the kidneys in cats.

Identification of Helicobacter spp. in gastrointestinal tract, pancreas and hepatobiliary system of stray cats.

The aim of the present study was to determine the presence of Helicobacter species in different parts of gastrointestinal tract, hepatobiliary system and pancreas of stray cats. Six different sites at the level of genus, gastric (H. heilmannii and H. felis) and enterohepatic species of Helicobacter were investigated in six cats using species-specific primers by polymerase chain reaction (PCR). Interestingly, DNA of enterohepatic spp. was detected in 1/6 duodenum, 2/6 colon and 1/6 pancreas specimens. Results of sequencing revealed that all of these four positive samples belong to Helicobacter canis. While cats have not been considered as a potential zoonotic danger for non-pylori Helicobacter infections, the results of current study show prompt re-evaluation of that view. To the best of our knowledge, this is the first study about distribution of Helicobcater spp. in gastrointestinal tract of cats.

Sugarcane fibre may prevents hairball formation in cats.

Hair ingested by licking during cat grooming can eventually coalesce into solid masses in cat gastrointestinal tract. It is believed that dietary fibre might reduce formation of these trichobezoars (hairballs). The effects of two insoluble fibre sources added to kibble diets were evaluated with respect to trichobezoar faecal excretion. Thirty-two cats and four diets were used in a randomised block design: a control diet without additional fibre, 10% added sugarcane fibre, 20% added sugarcane fibre or 10% added cellulose. Animals were fed for 42d and during three separate periods (days 15-17, 25-27 and 40-42), the cats were housed individually in metabolic cages and their faeces were totally collected. The faeces were evaluated and the trichobezoars were isolated and classified into small (<1cm), medium (1·1-2cm) or large (>2·1cm). Means were evaluated by repeated measures ANOVA and contrasts (P<0·05). Cats fed sugarcane fibre shown a linear reduction of small and medium trichobezoar excretion (number per cat per day; P=0·004) as well as a reduction in trichobezoar mass excretion (mg per cat per day; P<0·01). The control group showed increased faecal excretion of large trichobezoars (P=0·003), which were not present in the high sugarcane fibre group (P<0·006). No effect of cellulose was observed for any evaluated trait. Therefore, long fibres (sugarcane fibre) may cause greater peristaltic stimulation, increasing the propulsion of hair through the gut, but further research is needed to validate this mechanism. In conclusion, sugarcane fibre reduced faecal hairball elimination in cats, which may have clinical applications for the prevention of health problems related to trichobezoars.

Feline gastrointestinal microbiota

The close relationship between gastrointestinal (GI) microbiota and its host has an impact on the health status of an animal that reaches beyond the GI tract. A balanced microbiome stimulates the immune system, aids in the competitive exclusion of transient pathogens and provides nutritional benefits to the host. With recent rapid advances in high-throughput sequencing technology, molecular approaches have become the routinely used tools for ecological studies of the feline microbiome, and have revealed a highly diverse and complex intestinal ecosystem in the feline GI tract. The major bacterial groups are similar to those found in other mammals, with Firmicutes, Bacteroidetes, Actinobacteria and Proteobacteria constituting more than 99% of intestinal microbiota. Several nutritional studies have demonstrated that the feline microbiota can be modulated by the amount of soluble fibers (i.e., prebiotics) and macronutrients (i.e., protein content) in the diet. Initial clinical studies have suggested the presence of a dysbiosis in feline inflammatory bowel disease (IBD). Recently, metagenomic approaches have attempted to characterize the microbial gene pool. However, more studies are needed to describe the phylogenetic and functional changes in the intestinal microbiome in disease states and in response to environmental and dietary modulations. This paper reviews recent studies cataloging the microbial phylotypes in the GI tract of cats.

The absorption of bretylium and related quaternary ammonium salts from the alimentary tract.

Abstract N-Methyl-14C-labelled bretylium was injected into the lumen of segments of the gastrointestinal tract of cats prepared so that blood draining from these segments could be collected for analysis. The drug was not absorbed from the stomach. The concentration of drug in the venous blood from the duodenum rose steadily during 1.5–2 hr. but then declined to a value slightly exceeding that in the systemic blood. The greater part of the dose was not absorbed. Bretylium slowly traversed rat duodenum (mucosa to serosa) in vitro and the rate was not affected by factors that can influence carbohydrate metabolism. Transfer proceeded equally well from serosa to mucosa. To investigate means of obtaining better absorption of quaternary ammonium anti-adrenergic drugs a close analogue of bretylium bearing a choline residue was phosphorylated to give a phosphoric ester betaine (III). This was about twice as active by the oral route in cats as the parent drug, in which form it was excreted in the urine.

Phenotypical characterization, distribution and quantification of different mast cell subtypes in transmural biopsies from the gastrointestinal tract of cats with inflammatory bowel disease

In this study subtypes, distribution and number of mast cells were investigated within mucosa and submucosa of the gastrointestinal tract of 24 cats with inflammatory bowel disease (IBD) in comparison to 11 control cats. Paraffin sections of formalin-fixed transmural gastrointestinal biopsies from stomach, duodenum, jejunum, ileum and colon were examined. Mast cells were phenotyped and quantified based on their chymase and tryptase content, by applying a combined enzyme-histochemical and immunohistochemical double-labeling technique and on their heparin content by a metachromatic staining method (kresylecht-violet, MC KEV). Mast cells containing both chymase and tryptase were not found in any of the samples examined. Furthermore, in the stomach neither chymase (MC C) nor tryptase (MC T) bearing mast cells were detected. In cats with lymphocytic–plasmacytic enteritis or enterocolitis elevated numbers of MC T or MC C were identified in comparison to controls mainly located in the inflamed segments. The highest quantity of MC C was found in cats with eosinophilic gastroenterocolitis or enterocolitis in comparison to other IBD forms, but only minor numbers of MC T were detected in these cases. In cats with fibrosing enteropathy (FE) a decrease of MC C and mast cells containing heparin was detected in affected segments, while increased numbers of MC T were detected in all locations. The elevation in the number of MC T was higher in unaffected areas than in fibrotic regions. Regarding all IBD cases higher counts of MC C were found especially in the inflamed locations, whereas in unaffected segments increased numbers of MC T were detected. The clear predominance of MC C and MC T within the mucosa and of MC KEV within the submucosa of all cats examined possibly represents differences of the cytokine milieu within the intestinal layers. In FE, mast cells are possibly pivotal for the containment of the inflammatory process because of their antiinflammatory properties. The results of this study indicate that mast cells and their mediators are involved in the pathogenesis of different IBD forms in cats.

Mucosal defence along the gastrointestinal tract of cats and dogs

Diseases that are associated with infections or allergic reactions in the gastrointestinal and respiratory tracts are major causes of morbidity in both cats and dogs. Future strategies for the control of these conditions require a greater understanding of the cellular and molecular mechanisms involved in the induction and regulation of responses at the mucosal surfaces. Historically, the majority of the fundamental studies have been carried out in rodents or with tissues obtained from man, but the expanding range of reagents available for the study of farm and companion animals provides opportunities for study in a wider range of animals including cats and dogs. To date, these studies have tended to be focussed on characterising the cellular distributions in healthy animals and in groups of cats and dogs identified as having an increased risk of mucosal disturbance. Where species comparisons of mucosal immune systems have been made, the results have tended to be divided between monogastric and ruminant animals. It is then not surprising that the mucosal immune systems of both cats and dogs bear greatest similarity to that documented for man and pigs. For example, IgA is the dominant immunoglobulin in mucosal secretions of cats and dogs and oral tolerance can be induced following the introduction of novel antigens into the diet. Also like several other species, cats become transiently hypersensitive to the newly introduced dietary antigen prior to the establishment of tolerance. In contrast, there are a number of potentially important differences. In particular, there are significant differences between cats and dogs in the expression MHC class II molecules on gut epithelial cells. Similarly, it has been reported that cats have elevated numbers of intraepithelial lymphocytes (IEL) and that a proportion of these express surface IgM. It remains to be determined if these differences reflect the way in which the animals are maintained and if they may have greater biological significance.

Peptides do not induce contractions in gastrointestinal smooth muscle in calcium-free solution

1. Smooth muscle from six sites in the cat gastrointestinal tract was evaluated with respect to its ability to generate contractions in calcium-free solutions. 2. Membrane depolarization and carbachol, but not cholecystokinin or neurotensin, increased tension in smooth muscle segments of esophagus, corpus, duodenum, ileum, proximal colon and distal colon in calcium-free solution. 3. Substance-P produced a contractile response in the absence of calcium but only in the corpus and distal colon. 4. These findings indicate that peptide mediated release of intracellular calcium plays a minimal role in activation of cat gastrointestinal smooth muscle.

Exaggeration of the cholecystokinin-induced motor response in the cat gastrointestinal tract.

A stimulation of distal colonic motor activity was produced in anesthetized cats following intravenous administration of cholecystokinin. The contractile response elicited by cholecystokinin was not reduced following pretreatment with atropine. However, when animals were treated with agents which increased the net cholinergic input to the colon, a marked exaggeration of the subsequent cholecystokinin-induced response occurred. This cholinergically mediated exaggeration was produced following administration of the cholinergic agonist bethanechol, or after removal of tonic inhibitory systems mediated by prostaglandin or alpha-adrenergic input, whose blockade results in atropine-sensitive colonic stimulation. Cholecystokinin was also found to produce stimulation of motor activity in the pylorus, jejunum, proximal colon and gallbladder. Cholinergically mediated exaggeration of the cholecystokinin response was also present in the pylorus and proximal colon, but not gallbladder or jejunum. An inhibition of spontaneous motor activity was produced in the ileum or duodenum following cholecystokinin administration.

Arginine-vasopressin immunoreactive material in the gastrointestinal tract.

Like many other neuropeptides, vasopressin is not confined to the hypothalamic neurohypophysial system. Furthermore, vasopressin was found to be a potent vasoconstrictor in the rat jejunum, reducing myenteric artery flow. These associations were the basis of this investigation on the presence of vasopressin in the gastrointestinal (GI) tract by both RIA and immunohistochemistry. Portions of the gastrointestinal tract and pancreatic islets of the rat were extracted with 0.1 N HCl for RIA measurements of AVP content. Similar portions from the male cat GI tract were used for immunohistochemistry studies. Acid extracts of the GI tract were found to contain immunoreactive AVP with the highest concentration (pg/mg protein) in the fundus portion of the stomach (15.0 +/- 1.6) and slightly lower values down along the antrum-pylorus portion (6.7 +/- 0.6), proximal jejunum (8.6 +/- 0.2), distal ileum (9.7 +/- 0.3) and colon (11.9 +/- 0.5). In the pancreatic islets the concentration was much higher (72.0 pg/mg protein). The extract inhibition curves showed parallelism with the appropriate standard preparation of AVP in the specific RIA. Immunohistochemical localization showed IR-AVP in the nerve fibers around the myenteric plexus of the second portion of the duodenum. It was also found in fibers starting from where the myenteric plexus goes through the layer of muscle fibers, penetrating the submucosa and duodenal mucosa, ending near the capillaries situated along the basal side of the villous epithelium cells. Similar IR-AVP activity was found in cells located in the mucosal epithelium of the duodenum, jejunum, ileum, colon and rectum.(ABSTRACT TRUNCATED AT 250 WORDS)

Presence of γ-aminobutyric acid and glutamic acid decarboxylase in Auerbach's plexus of cat colon

Regional distributions of endogenous γ-aminobutyric acid (GABA) and ganglion cells in Auerbach's plexus were studied in the gastrointestinal tract of cats. GABA was determined by enzymatic and fluorometric assay. There was a positive correlation between the GABA content and the number of cells in this plexus. We analyzed the precise localization of GABA and glutamic acid decarboxylase (GAD) in individual layers, mucosa, circular and longitudinal muscles and Auerbach's plexus, from freeze-dried sections of cat colon by the enzymatic cycling method. Both GABA contents and GAD activity in Auerbach's plexus were highest in all 4 layers. Thus, the possibility that GABA is synthesized and localized within Auerbach's plexus has to be considered.