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PubMed1999

Transport of thiamine in human intestine: mechanism and regulation in intestinal epithelial cell model Caco-2.

The present study examined the intestinal uptake of thiamine (vitamin B(1)) using the human-derived intestinal epithelial cells Caco-2 as an in vitro model system. Thiamine uptake was found to be 1) temperature and energy dependent and occurred with minimal metabolic alteration; 2) pH sensitive; 3) Na(+) independent; 4) saturable as a function of concentration with an apparent Michaelis-Menten constant of 3.18 +/- 0.56 microM and maximal velocity of 13.37 +/- 0.94 pmol. mg protein(-1). 3 min(-1); 5) inhibited by the thiamine structural analogs amprolium and oxythiamine, but not by unrelated organic cations tetraethylammonium, N-methylnicotinamide, and choline; and 6) inhibited in a competitive manner by amiloride with an inhibition constant of 0.2 mM. The role of specific protein kinase-mediated pathways in the regulation of thiamine uptake by Caco-2 cells was also examined using specific modulators of these pathways. The results showed possible involvement of a Ca(2+)/calmodulin (CaM)-mediated pathway in the regulation of thiamine uptake. No role for protein kinase C- and protein tyrosine kinase-mediated pathways in the regulation of thiamine uptake was evident. These results demonstrate the involvement of a carrier-mediated system for thiamine uptake by Caco-2 intestinal epithelial cells. This system is Na(+) independent and is different from the transport systems of organic cations. Furthermore, a CaM-mediated pathway appears to play a role in regulating thiamine uptake in these cells.

Biological Transport↗
PubMed1981

Alpha-aminoisobutyric acid loss by rat small intestine: role of intestinal site and luminal contents.

Loss of amino acid into the lumen may be important in diarrheal states. Labeled alpha-aminoisobutyric acid (AIB) was given parenterally, and concentration gradients developed between lumen, intestinal tissue and plasma. After 24 h, we measured AIB loss into the intestinal lumen by recirculating isolated segments in situ under conditions of either net water absorption or net water secretion. Final 14C-AIB concentrations in intestinal tissue were 200-800 times that of lumen, 6--15 times that of serum. Despite increased total 14C-AIB loss during net water secretion, and based on the low luminal 14C-AIB concentrations, the contribution of amino acid loss to fecal nitrogen during osmotic diarrhea appears to be minimal.

Aminoisobutyric Acids↗
PubMed1984

The effect of concanavalin A and wheat germ agglutinin on the ultrastructure and permeability of rat intestine. A possible model for an intestinal allergic reaction.

Sprague-Dawley rats were exposed to lectins, either concanavalin A (Con A) or wheat germ agglutinin (WGA). The lectins were instilled into a ligated segment of the distal small intestine together with permeability markers, fluoresceinated dextran (MW 3,000) or a mixture of differently sized polyethylene glycols (MW 400, 600 and 1,000). WGA-treated rats showed a decreased permeability to small molecules (MW less than 600) of polyethylene glycol but an increase for a larger dextran molecule (MW 3,000). These effects as well as the morphological findings might mimic the situation in patients with food allergy or celiac disease. Con A-treated rats had decreased intestinal permeability to the larger dextran molecules (MW 3,000), whereas the passage of small molecules was unaffected and the ultrastructural effects were minute. The Con A-induced changes could result from a mucotractive effect, associated with a low-grade gut allergy. These observations suggest that lectins can affect both the ultrastructure and the permeability of the intestine, in a way assumed to mimic allergic reactions to food constituents.

Animals↗
PubMed1998

Fas ligand- mediated killing by intestinal intraepithelial lymphocytes. Participation in intestinal graft-versus-host disease.

In vitro studies have demonstrated that intestinal intraepithelial lymphocytes (IEL) are constitutively cytotoxic; however, the mechanism and target of their cytotoxicity are unknown. Apoptosis of intestinal epithelial cells (IEC) and an increase in IEL numbers are classical signs of intestinal graft-versus-host disease (GVHD), although whether IEL can mediate IEC apoptosis directly in GVHD is unclear. Recent evidence suggests that target epithelial organ injury observed in GVHD is predominantly Fas-mediated; therefore, we investigated the possibility that IEL induce apoptosis of IEC through a Fas-mediated mechanism. Here, we demonstrate that the IEL isolated from normal mice readily display potent Fas ligand (FasL)-mediated killing activity after CD3 stimulation, and that IEC express Fas, suggesting that IEC are potential targets for FasL-mediated killing by IEL. In vitro, IEL isolated from GVHD mice have markedly increased FasL-mediated killing potential and are spontaneously cytolytic toward host-derived tumor cells predominantly through a Fas-mediated pathway. In vivo transfer of IEL isolated from GVHD mice induced significantly more IEC apoptosis in F1 wild-type mice than in Fas-defective F1lpr mice. Thus, these results demonstrate that FasL-mediated death of IEC by IEL is a major mechanism of IEC apoptosis seen in GVHD.

Animals↗
PubMed2004

Studies on intestinal absorption of sulpiride (3): intestinal absorption of sulpiride in rats.

The aim of this study was to investigate whether the concomitant administration of the substrates or inhibitors of PEPT1, OCTN1, OCTN2, and P-glycoprotein affects the intestinal absorption of sulpiride in rats. The absorption of sulpiride from rat intestine was decreased by the substrates or inhibitors of PEPT1, OCTN1, and OCTN2. On the other hand, the absorption was increased by the substrates of P-glycoprotein. The effects of these concomitantly administered drugs on the pharmacokinetic behavior of sulpiride after oral administration in rats were investigated. Peak concentration (C(max)) and area under the plasma concentration-time curve (AUC(0-8 h)) of sulpiride were decreased by the concomitant administration of the substrates or inhibitors of PEPT1, OCTN1, and OCTN2. However, the same parameters were significantly increased by the concomitant administration of the substrates of P-glycoprotein. The present results suggest the possibility of drug-drug interaction during the absorption process in the small intestine due to the coadministration of sulpiride and these agents. These findings provide important information for preventing adverse effects and for ensuring the effectiveness of sulpiride and concomitantly administered drugs.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1982

Intestinal absorption of several beta-lactam antibiotics. III. Competitive inhibition behavior among zwitterionic beta-lactam antibiotics in the rat intestinal absorption.

Competitive inhibitory behavior among zwitterionic beta-lactam antibiotics in the rat intestinal absorption process was examined. Intestinal absorption of cephradine and cephalexin was significantly inhibited by cyclacillin. The mutual inhibition between these amino-cephalosporins was also observed. On the other hand, in the pretreatment experiments with cyclacillin, it was found that absorption of cephradine was significantly inhibited, but the inhibitory effect of cyclacillin was not observed for cephalexin. These results showed that cephradine had a common carrier-mediated transport mechanism with cyclacillin which is not present in the absorption process of cephalexin. It was postulated that the mutual inhibition between cephradine and cephalexin is based on the competitive inhibition in the accumulation or uptake by the intestinal mucosa.

Animals↗
PubMed1985

The mechanism of intestinal transport of sulfamethoxazole and the effect of chlorpromazine in rat everted intestine.

The mechanism of the intestinal transport of sulfonamides and the effect of chlorpromazine (CPZ) on it were studied using rat everted intestine in vitro. Sulfamethoxazole (SMZ) was accumulated in the serosal solution in the everted sac obeying the pH partition theory, while sulfisoxazole (SIX) was not accumulated despite the presence of the pH difference between the serosal and mucosal solutions. The reason was suggested that the microclimate pH on the mucosal surface of the intestine so decreased the amount of the unionized molecules of SIX that the transport rate of SIX was decreased to show no accumulation in the serosal solution within the sampling period. CPZ as well as metabolic inhibitors blocked the SMZ accumulation by inhibiting the growth of the pH difference. This effect was caused by the inhibition of the serosal alkalinization.

Animals↗
PubMed1975

[Effect of prostaglandin E1 on the isolated stomach, small intestine, bronchus and uterus of experimental animals and its intestinal effect in vivo].

The stomach, intestine and uterus were contracted by PGE1. Stimulating effects of ACh and serotonin were augmented in some of these organs, especially in guinea pig uterus. ACh- and serotonin-induced bronchial contraction, however, decreased after administration of PGE1. Bronchial relaxation induced by adrenaline or noradrenaline was unaffected or increased. Antiadrenergic effects were not detected in the organs tested. ACh-induced contractions of frog rectus abdominus was augmented by PGE. The potentiating effect of PGE1 was almost the same in degree as that of physotigmine, although cholinesterase inhibitory effect was not detected in PGE1. Intravenous injection of PGE1 (10 mug/kg) into rabbits caused a relaxation of the intestine, which was contrary to the result with the isolated organ. Administration of PGE1 (1 mug/100 g, i.p. or 0.1, 1 mug/100 g, i.v.) did not show any curative effects on intestinal paralysis in cecectomized rats. The mechasism of action of PGE1 on rat uterus was found to be calcium-dependant.

Abdominal Muscles↗
PubMed1986

[Electromyographical study on motor function of residual intestine after massive resection of small intestine].

Canine intestine 80% was resected, and the post-operative residual intestine was observed on its motor-function in time course by the use of electro-myographic test. The results are as follows. Post-operative frequency of electric discharge was reduced, and it was reduced at the residual jejunum in time course, while it was nearly constant at the residual ileum. Residual jejunum showed no significant change in the continuous time and amplitude of spike burst after operation. While residual ileum showed the post-operative increasing tendency. When the ratio of active phase, average of spike burst occurrences in one minute was regarded as index of intestinal excitability, the excitability was increased in both jejunum and ileum at earlier stage after operation. However, the ileum showed earlier recovery tendency. Electric discharge interval after resection became irregular, and the occurrence rate of antiperistaltic propagation was elevated. Residual ileum showed a longer tendency of one series of MMC after operation. Residual jejunum showed numerous occurrences of MMC up to 3 months after operation, there after, occurring interval of MMC was extended, and MMC-series showed the shortened tendency. Conduction velocity was higher after operation at the residual ileum, and it was not recovered even after 2-3 years, while residual jejunum showed a recovery trend with the peak at the 6th week after operation.

Animals↗
PubMed2001

Intestinal digestion of dietary and endogenous proteins along the small intestine of calves fed soybean or potato.

This study was conducted to investigate the quantitative and qualitative changes in dietary and endogenous protein components along the small intestine of calves. They were fed milk replacers in which protein was provided either by skim milk powder alone, as control diet, or by skim milk powder and a soy concentrate, a partially hydrolyzed soy protein isolate, or a potato protein concentrate (1:1 on a CP basis). The calves were continuously infused with the liquid milk substitute diets into the abomasum. Duodenal, jejunal, and ileal digesta were collected through T-piece cannulas. Digestibility (corrected for total endogenous protein) of dietary protein and the concentration of dietary, host endogenous, and bacterial proteins were estimated from the AA composition of digesta using multiple linear regression. The apparent digestibility of feed components increased linearly between the duodenum and the ileum. It was lower with the diets containing plant protein than with the control, especially at the ileum (85% for CP with soy concentrate, 73% with soy isolate, and 81% with potato concentrate vs 91% with skim milk powder). The real digestibility of dietary protein at the ileum was estimated to be 96, 95, 94, and 99%, respectively, for each of the dietary components. The partition of protein components in digesta between dietary, nonspecific endogenous, specific host endogenous, and(or) specific bacterial proteins varied along the small intestine and between diets at a given site. Intestinal apparent reabsorption of host endogenous protein was estimated to be equivalent to at least 86% of the jejunum flow. To conclude, the lower apparent digestibility of the plant protein sources studied resulted more from an enhanced loss of host and bacterial endogenous proteins than from decreased hydrolysis of dietary protein and absorption of their AA.

Amino Acids↗
PubMed1989

Intestinal permeability assessed with different-sized polyethylene glycols in children undergoing small-intestinal biopsy for suspected celiac disease.

The gastrointestinal permeability was assessed by means of an oral load of a mixture of different-sized polyethylene glycols (PEG 400 and PEG 1000) in 76 children undergoing small-intestinal biopsy because of suspected celiac disease. Children with a mucosal abnormality suggestive of celiac disease had a lower urinary recovery of larger PEG molecules. They also displayed an altered permeability barrier, as evidenced by a lower ratio of recovery between large (1074 Da) and small (370 Da) PEG molecules. Gluten elimination and gluten challenge caused a significant change in PEG recoveries in children undergoing repeated PEG tests. Repeated assessments of intestinal permeability by means of different-sized PEGs after gluten withdrawal and challenge could complement or indicate suitable time for performing small-intestinal biopsy in children with gluten intolerance.

Adolescent↗
PubMed1979

Thiamine intestinal transport and phosphorylation : a study in vitro of potential inhibitors of small intestinal thiamine-pyrophosphokinase using a crude enzymatic preparation.

Using as enzymatic source the cytoplasmatic fraction of enterocytes isolated from the rat small intestine, thiamine-pyrophosphokinase activity was studied with a radiometric method using [thiazole-2-(14)C] thiamine. The Km value for thiamine was 2.14 X 10(-6) M and V 0.87 nmol of thiamine pyrophosphate mg-1 protein h-1. Eleven thiamine structural analogs and derivatives were assayed for their inhibitory action on the small intestine thiamine-pyrophosphokinase activity. Their Ki values were : pyrithiamine, 2.25 X 10(-6) M; thiamine monophosphate, 4 X 10(-6) M; 2'-ethylthiamine, 8 X 10(-6) M; 2'-butylthiamine, 6 X 10(-6) M; chloroethylthiamine and dimethalium, 1.5 X 10(-5) M; amprolium, 1.8 X 10(-4) M; L-582571, 1.65 X 10(-4) M; oxythiamine, 4.2 X 10(-3) M. Of the miscellaneous compounds tested (toxopyrimidine, Na-pyrophosphate, choline, L-phenylalanine, ethyl-urethane and 5-fluorouracil), none had any inhibitory action on intestinal thiamine-pyrophosphokinase activity, even if used at concentrations hundred times higher than that of labelled thiamine.

Animals↗
PubMed1991

A case of intestinal hemorrhage due to small intestinal metastases from primary lung cancer.

Although intestinal metastases from lung cancer are not rare at postmortem studies, the development of clinically significant symptoms from the gastrointestinal metastases is very unusual. We report a case of small intestinal hemorrhage leading to intestinal perforation secondary to metastases from a large cell carcinoma of the lung in a 31-year-old man along with a review of the literature.

Adult↗
PubMed1999

Intestinal trefoil factor binds to intestinal epithelial cells and induces nitric oxide production: priming and enhancing effects of mucin.

Intestinal trefoil factor (ITF or TFF3), NO and epithelium-associated mucin have important roles in sustaining mucosal integrity in the gastrointestinal tract. In the present study we examined ITF-binding molecules on IEC-18 cells (an intestinal epithelial cell line) with the use of flow cytometry and localized these molecules on the cell surface by confocal microscopy. Furthermore, we studied the interaction of mucin and ITF and their co-operative effect on NO production by the epithelium. Stimulation of cells with mucin (5 mg/ml) for 90 min resulted in a 5-fold increase in ITF binding. Treatment of IEC-18 cells with actinomycin D or cycloheximide attenuated mucin-enhanced ITF binding. Ligand blot analysis confirmed the induction of ITF-binding protein in IEC-18 cells by mucin. These results indicate that transcriptional and translational mechanisms are involved in the effect of mucin. Treatment with ITF overnight resulted in a low level of nitrite production by the cells, a 5-fold increase over control, in a concentration-dependent manner. ITF-induced NO production was attenuated by 1400W, a selective type II nitric oxide synthase (NOS2) inhibitor. By immunoblotting we found that NOS2 was up-regulated by ITF treatment. Priming IEC-18 cells with mucin for 90 min enhanced the effect of ITF on NO production, suggesting that the up-regulation of ITF-binding molecules by mucin might be physiologically relevant. Taken together, these observations indicate (1) that ITF-binding molecules that are up-regulated by mucin exist on the intestinal epithelial surface, and (2) that ITF modulates epithelial NO production via the NOS2 pathway, which is enhanced by mucin.

Animals↗
PubMed2001

Nutritive value of protein from sea urchin, and its effects on intestinal leucine aminopeptidase and intestinal and hepatic gamma-glutamyltranspeptidase.

Seafoods are a rich source of easily digestible protein that also provides polyunsaturated fatty acids, vitamins and minerals for human nutrition. The purpose of this study was to determine the nutritive value of diets high in protein from two species of sea urchin (Paracentrotus lividus and Echinus esculentus) as compared to a high-quality reference protein such as casein, as well as the effects of these diets on leucine aminopeptidase and gamma-glutamyltranspeptidase, intestinal and hepatic enzymes. The test was carried out on three groups of male rats fed these diets for 23 days. The result of the nutritive parameters indicated that sea urchin, Echinus esculentus, were significantly lower than the casein protein except for food intake, and the nutritive parameters of sea urchin, Paracentrotus lividus, were similar to the values obtained for casein protein except for digestibility and net protein utilization. Intestinal leucine aminopeptidase activity was significantly lower (P < 0.05) in the group fed Paracentrotus lividus as compared to the group fed casein. Intestinal gamma-glutamyltranspeptidase showed a significantly higher activity in the group fed E. esculentus than in the two other groups and the hepatic gamma-glutamyltranspeptidase activity in the groups fed the two species of sea urchin were lower. Nutritive values suggested that these marine species are a good protein source and similar to casein. The activity of the enzymes under study must have been affected by the amino acid composition of the protein.

Amino Acids↗
PubMed1975

Studies of the effects of blockage of intestinal lymphatics. III. Temporary isolation of lymphedematous bowel from intestinal continuity.

Eight dogs underwent intestinal lymphatic block. Once intestinal lymphedema was established, a segment was excluded from continuity for four months and then restored to continuity. The lymphedema decreased during exclusion and reappeared after restoration to continuity. The relationship of the changes seen in the intestine following lymphatic block and to the changes observed in the bowel in regional enteritis suggests a pathogenetic role for lymphatic blockage and explains the pseudobeneficial effects of by-pass as well as the prompt recrudescence of pathology which follows reconstruction procedures.

Animals↗
PubMed2001

Suppression of intestinal polyps in Msh2-deficient and non-Msh2-deficient multiple intestinal neoplasia mice by a specific cyclooxygenase-2 inhibitor and by a dual cyclooxygenase-1/2 inhibitor.

Epidemiological studies suggest that nonsteroidal anti-inflammatory agents decrease the risk of colorectal cancer. This is believed to be mediated, at least in part, by inhibition of cyclooxygenase (COX) activity. There are two COX isoenzymes, namely the constitutively expressed COX-1 and the inducible COX-2. COX-2 is overexpressed in adenomas and colorectal cancers, and COX-2-specific inhibitors have been shown to inhibit intestinal polyps in Apc(Delta716) mice more effectively than dual COX-1/COX-2 inhibitors such as sulindac. Various Apc knockout mice, including the multiple intestinal neoplasia (Min) mouse and the Apc(Delta716) mouse, are limited by their lack of large numbers of colonic adenomas and aberrant crypt foci, the putative precursors of large-bowel polyps and cancers. Our DNA mismatch-repair-deficient Min mouse model (Apc+/-Msh2-/-) has genetic features of both familial adenomatous polyposis and hereditary nonpolyposis colorectal cancer, and most importantly, rapidly develops numerous small- and large-bowel adenomas, as well as colonic aberrant crypt foci. The purpose of this study was to determine the effects of COX inhibitors on intestinal adenomas and colonic aberrant crypt foci in this accelerated polyposis, mismatch-repair-deficient Min mouse model, in addition to a standard Min mouse model. Weanling Apc+/-Msh2-/- and Min mice were fed diets containing no drug, sulindac, or a specific COX-2 inhibitor (MF-tricyclic). Apc+/-Msh2-/- and Min mice were sacrificed after 4 weeks and 5 months on diet, respectively. Apc+/-Msh2-/- mice treated with MF-tricyclic had significantly fewer small-bowel polyps (mean +/- SD, 178 +/- 29) compared with mice on sulindac (278 +/- 80), or control diet (341 +/- 43; P < 0.001). There was no difference in numbers of large-bowel polyps or aberrant crypt foci in mice in the three groups. MF-tricyclic was also effective in reducing both small- and large-bowel polyps in Min mice. Western analysis demonstrated COX-2 expression in both large- and small-bowel polyps from mice of both genotypes. This study demonstrates that a specific COX-2 inhibitor is effective in preventing small-bowel polyps in mismatch-repair-deficient Min mice and both small- and large-bowel polyps in standard Min mice. Therefore, specific COX-2 inhibitors may be useful as chemopreventive and therapeutic agents in humans at risk for colorectal neoplasia.

Adenoma↗
PubMed1975

Intestinal uptake of macromolecules. IV.--The effect of pancreatic duct ligation on the breakdown of antigen and antigen-antibody complexes on the intestinal surface.

We have previously shown a consistent decrease in antigen absorption in vitro by ileal and jejunal gut sacs from orally or parenterally immunized rats in contrast to controls. In immunized rats, antigen appeared to be retained on the surface of the intestine and to be retained on the surface of the intestine and to undergo enhanced degradation by local proteases. This study was concerned with the role of pancreatic enzymes in degradation of antigen and antigen-antibody complexes. The breakdown of [125I]bovine serum albumin (BSA) by jejunal and ileal gut sacs from BSA-immunized, pancreatic duct-ligated rats was significantly decreased in comparison to that of BSA-immunized, sham-operated controls. Treatment of the immunized, pancreatic duct-ligated rats with pancreatic extracts prior to removal of the gut sacs, led to an increase in breakdown of [125I]BSA by the gut sacs in vitro. These findings suggest that pancreatic enzymes adsorbed to the surface of the intestine contribute to the proteolysis of antigens and antigen-antibody complexes at this site.

Animals↗