Prenatal arsenic exposure stymies gut butyrate production and enhances gut permeability in post natal life even in absence of arsenic deftly through miR122-Occludin pathway.

This discourse attempts to capture a few important dimensions of gut physiology like microbial homeostasis, short chain fatty acid (SCFA) production, occludin expression, and gut permeability in post-natal life of mice those received arsenic only during pre-natal life. Adult Balb/c mice were fed with 4 ppm arsenic trioxide in drinking water during breeding and gestation. After the birth of the pups, the arsenic water was withdrawn and replaced with clean drinking water. The pups were allowed to grow for 28 days (pAs-mice) and age matched Balb/c mice which were never exposed to arsenic served as control The pAs-mice showed a striking reduction in Firmicutes to Bacteroidetes (F/B) ratio coupled with a decrease in tight junction protein, occludin resulting in an increase in gut permeability, increased infiltration of inflammatory cells in the colon and decrease in common SCFAs in which butyrate reduction was quite prominent in fecal samples as compared to normal control. The above phenotypes of pAs-mice were mostly reversed by supplementing 5% sodium butyrate (w/w) with food from 21st to 28th day. The ability of butyrate in enhancing occludin expression, in particular, was dissected further. As miR122 causes degradation of Occludin mRNA, we transiently overexpressed miR122 by injecting appropriate plasmids and showed reversal of butyrate effects in pAs-mice. Thus, pre-natal arsenic exposure orchestrates variety of effects by decreasing butyrate in pAs-mice leading to increased permeability due to reduced occludin expression. Our research adds a new dimension to our understanding that pre-natal arsenic exposure imprints in post-natal life while there was no further arsenic exposure.

The novel form of amyloidosis derived from EGF-containing fibulin-like extracellular matrix protein 1 (EFEMP1) preferentially affects the lower gastrointestinal tract of elderly femalesa.

AIMS: To characterise the clinicopathological features of amyloidosis due to EGF-containing fibulin-like extracellular matrix protein 1 (EFEMP1), a newly described amyloid type. METHODS AND RESULTS: We identified cases by searching the Mayo Clinic amyloid liquid chromatography and tandem mass spectrometry typing database for specimens with the universal amyloid signature proteins, abundant EFEMP1 spectra and absence of other specific amyloid precursor proteins. We also developed an immunohistochemical stain for EFEMP1 applicable to formalin-fixed tissue sections and performed electron microscopy in one case. We identified 33 specimens from 32 patients with EFEMP1 amyloid. Most patients were female (91%) with a mean age of 75 years, and most specimens (94%) were from the bowel. EFEMP1 amyloid was incidentally identified in specimens biopsied/resected for a variety of clinical indications. In bowel specimens, EFEMP1 amyloid involved blood vessels and interstitium of the lamina propria, submucosa and/or muscularis propria. Although the EFEMP1 deposits were weakly to moderately Congo red-positive with absent to weak birefringence, they were strongly positive for EFEMP1 by immunohistochemistry, had the characteristic fibrillar ultrastructure of amyloid and were readily identified by mass spectrometry. CONCLUSIONS: EFEMP1 amyloid is a recently described novel amyloid type that predominantly affects the bowel of elderly females. Because EFEMP1 amyloid is only weakly Congo red-positive, it may be overlooked without a high index of suspicion. However, its characteristic microanatomical distribution is highlighted by immunohistochemistry and its identity is readily confirmed by mass spectrometry. Based on its distinctive features, we propose that EFEMP1 amyloidosis be considered a new amyloid type.

Relative Abundance of SARS-CoV-2 Entry Genes in the Enterocytes of the Lower Gastrointestinal Tract.

There is increasing evidence of gastrointestinal (GI) infection by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). We surveyed the co-expression of SARS-CoV-2 entry genes ACE2 and TMPRSS2 throughout the GI tract to assess potential sites of infection. Publicly available and in-house single-cell RNA-sequencing datasets from the GI tract were queried. Enterocytes from the small intestine and colonocytes showed the highest proportions of cells co-expressing ACE2 and TMPRSS2. Therefore, the lower GI tract represents the most likely site of SARS-CoV-2 entry leading to GI infection.

SATB2 in neuroendocrine neoplasms: strong expression is restricted to well-differentiated tumours of lower gastrointestinal tract origin and is most frequent in Merkel cell carcinoma among poorly differentiated carcinomas.

AIMS: Special AT-rich sequence-binding protein 2 (SATB2) is a transcriptional regulator with critical roles in brain, craniofacial and skeletal development. It has emerged as a key marker of lower gastrointestinal (GI) tract columnar epithelial and osteoblastic differentiation. Transcription factor immunohistochemistry is useful in assigning site of origin in well-differentiated neuroendocrine tumours (NETs), and has had a limited role in poorly differentiated neuroendocrine carcinomas (NECs). This study sought to evaluate the role of SATB2 in assigning site of origin in neuroendocrine epithelial neoplasms. METHODS AND RESULTS: Tissue microarrays were constructed from the following: 317 NETs (37 thyroid, 46 lung, 16 stomach, 12 duodenum, 70 pancreas, 106 jejunoileum, 24 appendix, and six rectosigmoid), 44 phaeochromocytomas/paragangliomas, and 79 NECs (29 Merkel cell, 30 lung, and 20 extrapulmonary visceral); nine appendiceal and 19 rectal NETs were examined in whole sections. SATB2 immunohistochemistry was scored for extent (%) and intensity (0-3+), with an H-score being calculated. SATB2 was expressed by 96% of rectosigmoid NETs, 79% of appendiceal NETs, and only 7% of other well-differentiated neoplasms (P < 0.0001). Expression in lower GI tract NETs (median H-score of 255) was stronger than in other positive tumours (median H-score of 7) (P < 0.0001). Any SATB2 expression was 86% sensitive/93% specific for lower GI tract origin. SATB2 was expressed by 79% of Merkel cell carcinomas (median H-score of 300), 33% of lung NECs (median H-score of 23), and 60% of extrapulmonary visceral NECs (median H-score of 110), with stronger expression in Merkel cell carcinoma (P < 0.001). At an H-score cutoff of ≥150, SATB2 was 69% sensitive/90% specific for Merkel cell carcinoma. CONCLUSIONS: SATB2 is frequently and strongly expressed by lower GI tract NETs; we have adopted it as our rectal NET marker. Relatively frequent and strong expression in Merkel cell carcinoma may have value in assigning NEC site of origin.

Expression of P53, HER2 and Ki67 proteins in rats subjected to bladder augmentation with stomach, colon and ileum.

PURPOSE: To study the expression of HER2, p53 and Ki67 proteins in cystoplasties. METHODS: Sixty rats were distributed randomly into three groups of 20 animals. Bladder augmentation was held to increase with ileum (Group I), colon (Group II) and stomach (Group III). Tissue samples of neobladder was collected from each rat to its own control. The animals were sacrificed after 12 weeks. The neobladder was withdrawn for immunohistochemistry analysis of p53, HER2 and Ki67 expression. Wilcoxon and Mann-Whitney tests were used for statistical study. RESULTS: There were no significant changes in the expression of p53 and HER2 proteins. It was observed significant increase (p<0.0001) in Ki67 expression in all groups, when compared with their respective controls. When the study groups were compared with each other, there was increase of cell proliferation in the largest gastrocystoplasties in respect of ileocystoplasties (p=0.004) and colocystoplasties (p=0.003). CONCLUSION: We observed significant increase of cell proliferation characterized by Ki67 protein in the digestive tract of the ileocystoplasties, the colocystoplasties and the gastrocystoplasties and this increase was significantly greater in gastrocystoplasties.

Genomic organization and expression of insulin receptors in grass carp, Ctenopharyngodon idellus.

Insulin receptors have been demonstrated to be involved in embryogenesis, food intake regulation and glucose metabolism in several fish, while more researchis needed for further understanding. In this study, the complete coding sequence (CDS) of insulin receptor a (insra) gene and insulin receptor b (insrb) gene in grass carp were obtained, the CDS were 4068 bp and 4514 bp in length, encoding 1355 aa protein and 1351 aa protein. Both of insra and insrb in grass carp showed high amino acid identities with other fish. Insra and insrb genes were widely expressed in all tested tissues with an overlapping but distinct expressions. The high levels of insra mRNA were distributed in hindgut and heart tissues. The insrb gene showed the highest expression levels in liver and hindgut. We also proved that two forms of grass carp insulin receptors participate in the regulation of blood glucose and might act differently. Phylogenetic analysis confirmed that different isoforms of fish insulin receptors are derived from two distinct genes, which was inconsistent with the generation of mammalian insulin receptors. Synteny analyses of insulin receptor genes showed that genes surrounding the insulin receptor genes were conserved in fish. Arhgef18, PEX11G, humanC19orf45 genes were highly conserved among mammal species. However, no conserved synteny was observed among fish, mammals, avians and amphibians.

Expression of P53, HER2 and Ki67 proteins in rats subjected to bladder augmentation with stomach, colon and ileum

PURPOSE: To study the expression of HER2, p53 and Ki67 proteins in cystoplasties. METHODS: Sixty rats were distributed randomly into three groups of 20 animals. Bladder augmentation was held to increase with ileum (Group I), colon (Group II) and stomach (Group III). Tissue samples of neobladder was collected from each rat to its own control. The animals were sacrificed after 12 weeks. The neobladder was withdrawn for immunohistochemitry analysis of p53, HER2 and Ki67 expression. Wilcoxon and Mann-Whitney tests were used for statistical study. RESULTS: There were no significant changes in the expression of p53 and HER2 proteins. It was observed significant increase (p<0.0001) in Ki67 expression in all groups, when compared with their respective controls. When the study groups were compared with each other, there was increase of cell proliferation in the largest gastrocystoplasties in respect of ileocystoplasties (p=0.004) and colocystoplasties (p=0.003). CONCLUSION: We observed significant increase of cell proliferation characterized by Ki67 protein in the digestive tract of the ileocystoplasties, the colocystoplasties and the gastrocystoplasties and this increase was significantly greater in gastrocystoplasties.

Effects of iron supplementation on dominant bacterial groups in the gut, faecal SCFA and gut inflammation: a randomised, placebo-controlled intervention trial in South African children.

Fe supplementation is a common strategy to correct Fe-deficiency anaemia in children; however, it may modify the gut microbiota and increase the risk for enteropathogenic infection. In the present study, we studied the impact of Fe supplementation on the abundance of dominant bacterial groups in the gut, faecal SCFA concentration and gut inflammation in children living in rural South Africa. In a randomised, placebo-controlled intervention trial of 38 weeks, 6- to 11-year-old children with Fe deficiency received orally either tablets containing 50 mg Fe as FeSO4 (n 22) for 4 d/week or identical placebo (n 27). In addition, Fe-sufficient children (n 24) were included as a non-treated reference group. Faecal samples were analysed at baseline and at 2, 12 and 38 weeks to determine the effects of Fe supplementation on ten bacterial groups in the gut (quantitative PCR), faecal SCFA concentration (HPLC) and gut inflammation (faecal calprotectin concentration). At baseline, concentrations of bacterial groups in the gut, faecal SCFA and faecal calprotectin did not differ between Fe-deficient and Fe-sufficient children. Fe supplementation significantly improved Fe status in Fe-deficient children and did not significantly increase faecal calprotectin concentration. Moreover, no significant effect of Fe treatment or time × treatment interaction on the concentrations of bacterial groups in the gut or faecal SCFA was observed compared with the placebo treatment. Also, there were no significant differences observed in the concentrations of any of the bacterial target groups or faecal SCFA at 2, 12 or 38 weeks between the three groups of children when correcting for baseline values. The present study suggests that in African children with a low enteropathogen burden, Fe status and dietary Fe supplementation did not significantly affect the dominant bacterial groups in the gut, faecal SCFA concentration or gut inflammation.

Contribution of TRPV1 and multidrug resistance proteins in the permeation of capsaicin across different intestinal regions.

OBJECTIVE: The aim of the study was to observe the characteristic of permeation of capsaicin across jejunum, ileum and colon in the rat, and to investigate the role of transient receptor potential cation channel (TRPV1). The interaction of capsaicin with P-glycoprotein (P-gp), multidrug resistance-associated protein 2 (MRP2) and breast cancer resistance protein (BCRP) was also investigated. METHOD: The transport of capsaicin across three intestinal segments in rats was investigated using Ussing-chamber System. RESULTS: The permeability of capsaicin across the colonic ileac or jejunal membrane was significantly different in M-S direction (11.679 ± 2.001, 5.336 ± 1.248, 1.395 ± 0.673, ×10(-6)cm/s). TRPV1 non-competitive antagonist ruthenium red significantly decreased the permeability of capsaicin in M-S direction across colonic membrane. The permeability of capsaicin could also be inhibited unconventionally by the BCRP inhibitor novobiocin in M-S direction across colon. However, either the P-gp inhibitor verapamil or the MRP2 inhibitor probenecid did not affect the transport of capsaicin in all three segments. CONCLUSION: We firstly proved that the permeability of capsaicin across colon was significantly higher than that across jejunum or ileum. Furthermore, TRPV1 might mediate the transport of capsaicin across the intestinal membrane. Therefore, the colon-specific highest permeation of capsaicin could be the consequence of the colon-specific distribution of TRPV1. For another, there may be another transport pathway mediating the permeation of capsaicin in M-S direction, which could be inhibited by novobiocin.

Spatio-temporal expression of HOX genes in human hindgut development.

BACKGROUND: Hox genes belong to a highly conserved subgroup of the homeobox gene superfamily. Studies of animal models have emphasized their role in defining the body plan by their coordinated expression along the body axis during ontogeny. Although an important role of HOX genes in human development is assumed, little is known about their expression during human ontogenesis. Therefore, we investigated the expression of the nine most posterior members of the HOXA, HOXB, HOXC, and HOXD clusters in embryonic hindgut between weeks 6 to 12 and in adult rectal tissue. RESULTS: Applying in situ hybridization and immunohistochemistry, we observed expression of HOXA11, HOXA13, HOXD12, and HOXD13 in developmental week 6. However, expression of HOXD12 faded during weeks 7 and 8, and then became increasingly re-expressed during week 9 in humans. With the exception of HOXD13, all expressed HOX genes dropped below detection limits in week 11. Adult rectal tissue displayed distinct HOXA11, HOXA13, HOXD12, and HOXD13 expression patterns within the rectal layers. CONCLUSIONS: Our data suggest a strict spatio-temporal regulation of HOX gene expression during human development, supporting the idea of their role as key regulators. Nonetheless, the expression pattern of distinct HOX genes differs markedly from animal models.

Effect of purified ß-glucans derived from Laminaria digitata, Laminaria hyperborea and Saccharomyces cerevisiae on piglet performance, selected bacterial populations, volatile fatty acids and pro-inflammatory cytokines in the gastrointestinal tract of pigs.

ß-Glucans have been identified as natural biomolecules with immunomodulatory activity. The first objective of the present study was to compare the effects of purified ß-glucans derived from Laminaria digitata, L. hyperborea and Saccharomyces cerevisiae on piglet performance, selected bacterial populations and intestinal volatile fatty acid (VFA) production. The second aim was to compare the gene expression profiles of the markers of pro- and anti-inflammation in both unchallenged and lipopolysaccharide (LPS)-challenged ileal and colonic tissues. ß-Glucans were included at 250 mg/kg in the diets. The ß-glucans derived from L. hyperborea, L. digitata and S. cerevisiae all reduced the Enterobacteriaceae population (P<0·05) without influencing the lactobacilli and bifidobacteria populations (P>0·05) in the ileum and colon. There was a significant interaction between gastrointestinal region and ß-glucan source in the expression of cytokine markers, IL-1α (<0·001), IL-10 (P<0·05), TNF-α (P<0·05) and IL-17A (P<0·001). ß-Glucans did not stimulate any pro- or anti-inflammatory cytokine markers in the ileal epithelial cells. In contrast, the expression of a panel of pro- and anti-inflammatory cytokines (IL-1α, IL-10, TNF-α and IL-17A) was down-regulated in the colon following exposure to ß-glucans from all the three sources. However, the data suggest that the soluble ß-glucans derived from L. digitata may be acting via a different mechanism from the insoluble ß-glucans derived from L. hyperborea and S. cerevisiae, as the VFA profile was different in the L. digitata-treated animals. There was an increase in IL-8 gene expression (P<0·05) in the gastrointestinal tract from the animals exposed to L. digitata following an LPS ex vivo challenge that was not evident in the other two treatment groups. In conclusion, ß-glucans from both seaweed and yeast sources reduce Enterobacteriaceae counts and pro-inflammatory markers in the colon, though the mechanisms of action may be different between the soluble and insoluble fibre sources.

Apoptosis signalling activated by TNF in the lower gastrointestinal tract--review.

The tumor necrosis factor (TNF) gene is an immediate early gene, rapidly transcribed in a variety of cell types following exposure to a broad range of pathogens and signals of inflammation and stress. Regulation of TNF gene expression at the transcriptional level is cell type- and stimulus-specific, involving epigenetic mechanisms or miRNAs. A better knowledge of the molecular mechanisms that control TNF gene regulation and TNF signalling will provide deeper understanding of the initiation and development of apoptotic and inflammatory processes triggered by TNF cytokine in the gut. The described efforts to embed TNF in clinical treatment regiments reflect its attractive effectiveness in killing tumor cells. Whether the described strategies will achieve the success of incorporating TNF in lower gastrointestinal tract therapy for inflammatory diseases and cancer remains to be determined.

Localization of the orexin system in the gastrointestinal tract of fallow deer.

The aim of the present study was to investigate by immunohistochemistry the presence and distribution of the orexin system in the stomach and gut of fallow deer. Abundant orexin A-positive cells were localized in the middle and basal portions of the mucosal glands of the cardial and fundic regions of the stomach. In the same gastric areas, orexin B-positive cells were also found, mainly localized in the basal portion of glands. In the intestinal tract, orexin-containing cells were occasionally found in the duodenal epithelium and in the rectal intestinal glands. Immunoreactivity for orexin receptors, type 1 and 2 (OX1R and OX2R), was not detected in the same stomach regions. OX1R-immunopositivity was observed in the enteric neuron ganglia localized in the submucosal and muscular intestinal layers, while OX2R-immunopositivity was found close in contact with the cytoplasmic membrane of epithelial cells in the small intestine.

Pretreatment with diphenoxylate hydrochloride/atropine sulfate (Lomotil) does not decrease physiologic bowel FDG activity on PET/CT scans of the abdomen and pelvis.

PURPOSE: Physiologic uptake of 2-[(18)F]-fluoro-2-deoxy-D: -glucose (FDG) by bowel can confound positron emission tomography/computed tomography (PET/CT) assessment for abdominal pathology, particularly within the bowel itself. We wished to determine if oral administration of the antimotility agent, Lomotil (5 mg diphenoxylate hydrochloride/0.05 mg atropine sulfate; G.D. Searle and Company, a division of Pfizer), prior to PET/CT scanning would reduce physiologic uptake of FDG by the small bowel and colon (lower gastrointestinal [GI] tract). PROCEDURES: Patients undergoing PET/CT scans for lymphoma were enrolled in a prospective, randomized, double-blinded study and received either 10 mL water (control group) or 10 mL Lomotil (experimental group) orally 30-60 min prior to scanning. Scans were reviewed independently by two blinded experienced readers and scored for the degree of FDG activity in the lower GI tract relative to liver activity. RESULTS: The administration of Lomotil prior to PET/CT scanning did not reduce physiologic FDG activity in the small bowel and colon. In contrast, increased radiotracer uptake by the lower GI tract was observed in the Lomotil group compared to the control group. CONCLUSIONS: Pretreatment with Lomotil prior to PET/CT scanning confers no benefit toward the reduction of physiologic FDG uptake by the small bowel and colon.

Lower gastrointestinal functions.

The human colon serves to absorb water and electrolytes, store intraluminal contents until elimination is socially convenient, and salvage nutrients by bacterial metabolism of carbohydrates that have not been absorbed in the small intestine. The anorectum is responsible for fecal continence and defecation. This article is a broad perspective of the current status and a personal perspective of future challenges in understanding lower gastrointestinal functions in health and disease in humans.

Immunolocalization of histamine H3 receptors on endocrine cells in the rat gastrointestinal tract.

The histamine H3 receptor (H3R) has been identified in the gastrointestinal tract of the rat by immunohistochemistry, using the first validated anti-H3 receptor antibody. Immunoreactivity to H3R was exclusively localized to the endocrine cells scattered in the gastrointestinal mucosa, with positive cells being prominently abundant in the gastric fundus, while they were rarely found in the other regions. In the fundus, positive cells were distributed in the lower half of the mucosa and their number significantly decreased after a 24 h-fasting period. Double-labeling studies were undertaken to identify the H3R-immunoreactive cell types in the fundic and antral mucosa. The H3R-immunoreactive cells were positive for chromogranin A. In the fundus, approximately 90% of cells positive to H3R were also positive to the histamine-forming enzyme, histidine decarboxylase. None of the cells expressing H3R displayed immunoreactivity for gastrin, somatostatin or ghrelin. Location, the influence of food deprivation and colocalization with histidine decarboxylase indicate that H3R positive cells correspond to the enterochromaffin-like cells (ECL).

Expression and localization of an aquaporin-1 homologue in the avian kidney and lower intestinal tract.

In birds, the kidneys and lower intestine function in osmoregulation. A 271-amino acid homologue to aquaporin-1 (AQP-1) was isolated from the kidneys, cecae, proximal and distal rectum, and coprodeum of the lower intestine in the house sparrow (Passer domesticus). This protein has six transmembrane domains connected by two cytoplasmic loops and three extracellular loops. It exhibits 94%, 88%, and 78% homology to AQP-1 sequences of chicken, human and toad, respectively. Many of the highly conserved amino acids that are characteristic of AQP-1 are found in the sparrow sequence. RT-PCR was performed and the presence of AQP-1 mRNA was detected in the kidney and all four regions of the lower intestine. Immunoblots of total protein identified a 28-kDa non-glycosylated AQP-1 band and a 56-kDa glycosylated AQP-1 band in the kidney and all four regions of the lower intestine. Immunohistochemistry demonstrated the presence of the AQP-1 protein within both the renal cortex and medulla. In the lower intestine, the protein was present in the proximal rectum, distal rectum, and in the coprodeum. As AQP-1 functions to allow water movement across mammalian cell membranes, its presence in water-permeable cells in a bird suggests it may have a similar function.

Transport of nicotinate and structurally related compounds by human SMCT1 (SLC5A8) and its relevance to drug transport in the mammalian intestinal tract.

UNLABELLED: PURPOSE. To examine the involvement of human SMCT1, a Na+-coupled transporter for short-chain fatty acids, in the transport of nicotinate/structural analogs and monocarboxylate drugs, and to analyze its expression in mouse intestinal tract. MATERIALS AND METHODS: We expressed human SMCT1 in X. laevis oocytes and monitored its function by [14C]nicotinate uptake and substrate-induced inward currents. SMCT1 expression in mouse intestinal tract was examined by immunofluorescence. RESULTS: [14C]Nicotinate uptake was several-fold higher in SMCT1-expressing oocytes than in water-injected oocytes. The uptake was inhibited by short-chain/medium-chain fatty acids and various structural analogs of nicotinate. Exposure of SMCT1-expressing oocytes to nicotinate induced Na+-dependent inward currents. Measurements of nicotinate flux and associated charge transfer into oocytes suggest a Na+:nicotinate stoichiometry of 2:1. Monocarboxylate drugs benzoate, salicylate, and 5-aminosalicylate are also transported by human SMCTI. The transporter is expressed in the small intestine as well as colon, and the expression is restricted to the lumen-facing apical membrane of intestinal and colonic epithelial cells. CONCLUSIONS: Human SMCTI transports not only nicotinate and its structural analogs but also various monocarboxylate drugs. The transporter is expressed on the luminal membrane of the epithelial cells lining the intestinal tract. SMCT1 may participate in the intestinal absorption of monocarboxylate drugs.

mRNA expression and binding sites for alpha2-adrenergic receptor subtypes in muscle layers of the ileum and spiral colon of dairy cows.

OBJECTIVE: To measure maximum binding capacity (B(max)) and levels of mRNA expression for alpha(2)-adrenergic receptor (AR) subtypes in ileal and colonic muscle layers of healthy dairy cows. SAMPLE POPULATION: Ileal and colonic muscle specimens from 6 freshly slaughtered cows. PROCEDURES: Ileal and colonic muscle layers were obtained by scraping the mucosa and submucosa from full-thickness tissue specimens. Level of mRNA expression for alpha(2)-AR subtypes was measured by real-time reverse transcriptase-PCR analysis and expressed relative to the mean mRNA expression of glyceraldehyde phosphate dehydrogenase, ubiquitin, and 18S ribosomal RNA. Binding studies were performed with tritiated RX821002 ((3)H-RX821002) and subtype-selective ligands as competitors. RESULTS: mRNA expression for alpha(2AD)-, alpha(2B)-, and alpha(2C)-AR subtypes was similar in ileal and colonic muscle layers. The mRNA expression for alpha(2AD)-AR was significantly greater than that for alpha(2B)- and alpha(2C)-AR subtypes, representing 92%, 6%, and 2%, respectively, of the total mRNA. Binding competition of (3)H-RX821002 with BRL44408, imiloxan, and MK-912 was best fitted by a 1-site model. The B(max) of alpha(2AD)- and alpha(2C)-AR sub-types was greater than that of alpha(2B)-AR. The B(max) and level of mRNA expression were only correlated (r = 0.8) for alpha(2AD)-AR. Ratio of B(max) to mRNA expression for alpha(2C)-AR was similar to that for alpha(2B)-AR, but significantly greater than for alpha(2AD)-AR. CONCLUSIONS AND CLINICAL RELEVANCE: Subtypes of alpha(2)-AR in bovine intestinal muscle layers are represented by a mixture of alpha(2AD)- and alpha(2C)-ARs and of alpha(2B)-AR at a lower density. Information provided here may help in clarification of the role of AR subtypes in alpha(2)-adrenergic mechanisms regulating bovine intestinal motility.

Endocrine regulation of ion transport in the avian lower intestine.

The lower intestine (colon and coprodeum) of the domestic fowl maintains a very active, transporting epithelium, with a microvillus brush border, columnar epithelial cells, and a variety of transport systems. The colon of normal or high salt-acclimated hens expresses sodium-linked glucose and amino acid cotransporters, while the coprodeum is relatively inactive. Following acclimation to low salt diets, however, both colon and coprodeum shift to a pattern of high expression of electrogenic sodium channels, and the colonic cotransporter activity is simultaneously downregulated. These changes in the transport patterns seem to be regulated, at least in part, by aldosterone. Our recent work with this tissue has focused on whether aldosterone alone can account for the low salt pattern of transport. Other work has looked at the changes in morphology and in proportions of cell types that occur during chronic acclimation to high or low salt diets, and on a cAMP-activated chloride secretion pathway. Recent findings suggesting effects of other hormones on lower intestinal transport are also presented.