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PubMedDate not supplied

Sulfation and glucuronidation of benzo[a]pyrene-7,8-dihydrodiol in intestinal mucosa of channel catfish (Ictalurus punctatus).

Intestinal metabolism plays a significant role in the bioavailability of ingested environmental toxicants. In this study, the potential for first pass, phase 2 biotransformation of benzo[a]pyrene-7,8-dihydrodiol (BaP-7,8-diol) in intestinal mucosa was examined. Sulfotransferase and Uridine 5'-Diphospho-Glucuronyl-transferase activity were measured in cytosol, and microsomes respectively. Radiolabeled conjugation products were analyzed by TLC and high-performance liquid chromatography (HPLC). The results indicated that BaP-7,8-diol was a poor substrate for intestinal sulfotransferase. Vmax for the sulfation of BaP-7,8-diol was 0.002 nmol mg-1 min-1, which is at least three orders of magnitudes lower than the Vmax for phenolic BaP metabolites. Studies with 3'phosphoadenosine-5' phosphosulfate (PAP)-35S as co-substrate showed that an unidentified compound in the reaction mixture was sulfated, dependent on the BaP-7,8-diol concentration. This could indicate that BaP-7,8-diol was interacting with a regulatory site on the enzyme and stimulated sulfation of an endogenous molecule in cytosol. Kinetic analysis of microsomal glucuronidation resulted in a Vmax of 0.30 nmol mg-1 min-1 (+/- 0.06 S.D., n = 4), with a Km of 23.39 microM (+/- 2.66 S.D.). The Km for the co-substrate UDP-glucuronic acid was approximately 43 microM. The slow rates for sulfation and glucuronidation of BaP-7,8-diol may explain its relatively high systemic availability when ingested or produced by intestinal phase 1 enzymes.

Animals↗

PubMed1977

Effect of folate deficiency of the intestinal mucosa on jejunal transport in the rat.

The role of folate deficiency in the pathogenesis of the abnormalities of structure and transport of the small intestine that are often present in certain disorders such as alcoholism is unclear. One reason for this is that the folate status of the intestinal mucosa has never been ascertained in humans. Previous investigations have shown that a deficient diet supplemented with sulfa does produce folate deficiency of the intestinal mucosa in weanling rats and that this is associated with diarrhea and structural abnormalities of the jejunum. In the present study, we used then in vivo marker perfusion technique to examine the jejunal transport of water, sodium, xylose, glucose, and L-leucine in such folate-deficient rats. Supplementation of the normal diet with sulfa did not produce folate deficiency of the intestinal mucosa, but it was associated with a moderate reduction in water absorption; this was attributed to cecal enlargement in these rats. Rats placed on a folate-deficient diet plus sulfa developed markedly depressed serum and jejunal folate concentrations, net secretion of water and sodium, and persistent diarrhea; absorption of xylose, glucose, and L-leucine remained normal, however. Folate repletion of these rats by water and sodium transport to absorption ano cessation of diarrhea. These observations indicate that folate deficiency of the intestinal mucosa alters the transport of water and electrolytes but not that of such solutes as xylose, glucose, and L-leucine. They suggest that when transport abnormalities of these solutes occur in folate-deficient alcoholics, this in not due to the folate deficiency but rather to other pathogenic factors such as ethanol.

Animals↗

PubMed1991

Distribution of vasoactive intestinal polypeptide (VIP) binding in circular muscle and characterization of VIP binding in canine small intestinal mucosa.

The present study examined the localization and characterization of [125I]vasoactive intestinal polypeptide (VIP) binding to synaptosomes and enterocyte membranes using preparations made from homogenized canine intestinal mucosa and compared it to [3H]saxitoxin binding and VIP-immunoreactive content (markers for synaptosomes). The highest [125I]VIP binding was located in the P2 fraction and was correlated with the locations of maximal [3H]saxitoxin binding and VIP-immunoreactive content. This correlation indicates that VIP receptors are present on synaptosomes of canine small intestinal mucosa. A fraction enriched in synaptosomes contained a high density of saturable VIP receptors (352 +/- 26.40 fmol/mg) having high affinity (Kd, 0.23 nM) for [125I]VIP. Studies of association and dissociation of [125I]VIP to this site revealed that binding was fully reversible and yielded a Kd value similar to that from equilibrium binding. Competition binding experiments suggested the presence of two binding sites, a high and a low affinity binding site. The order of competition potency was VIP greater than peptide histidine isoleucine greater than secretin greater than peptide histidine methionine greater than or equal to [D-Ala4]VIP greater than or equal to [Phe1]VIP greater than VIP10-28 greater than [4-Cl-D-Phe6-Leu17]VIP. All these competitors displaced all specifically bound VIP. VIP, peptide histidine isoleucine and secretin interacted differentially with each of the two binding sites. Peptide histidine methionine, [D-Ala4]VIP, [Phe1]VIP, VIP10-28 and [4-Cl-D-Phe6-Leu17]VIP interacted with a single low affinity at all binding sites. Other VIP binding sites were sought in circular muscle and submucosa.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1991

[Synthesis of glucose-6-phosphatase in small intestine mucosa during experimental coccidiosis in suckling piglets].

Glucoso-6-phosphatase activity (EC. 3.1.3.9.) was evaluated microdensitometrically in the small intestine mucosa of 19 conventional piglets infected with Eimeria debliecki coccidium oocysts (infection dose of 200,000 oocysts) on day 1 after delivery (DAD). The synthesis of the observed hydrolase was followed within days 1 to 10 after infection (DAI). The activity of the same enzyme was also determined in four control conventional piglets at the age of two to five days. The small intestine mucosa of healthy piglets was found to have relatively balanced glucoso-6-phosphatase concentrations in all observed sections (duodenum, middle and posterior jejunum and ileum). The topographic gradient failed to be demonstrated in control piglets. In piglets experimentally infected with E. debliecki coccidium the glucoso-6-phosphatase activity was decreasing during infection already since DAI 1. The enzyme hypoactivity was still lower in the following days and reached the minimum value at the end of the target period (DAI 10), when its value made only 33% of the concentration recorded in the intestine mucosa of control piglets. The topographic predisposition to the lower activity of glucoso-6-phosphatase was not found to be high. The only exception are DAI 6 and 7, when the lowest enzyme concentration was observed in the duodenum mucosa (52% on DAI 6; 54% on DAI 7). The activity of the observed enzyme was higher in the other sections of small intestine (57% on DAI 6; 62% on DAI 7).

Animals↗

PubMed1980

Purification of phytase from rat intestinal mucosa.

Phytase has been purified from intestinal mucosa of rats fed on a phytic acid-enriched diet. The purification consisted of four steps: homogenate preparation, ultrafiltration procedure, DEAE cellulose chromatography, and Sephadex G-100 chromatography. The enzyme was purified 828-fold, as can be seen from the polyacrylamide gel electrophoresis pattern.

6-Phytase↗

PubMed1989

Effect of dietary fat on the small intestinal mucosa.

The presence of food within the small intestinal lumen promotes mucosal cell proliferation. To define the trophic role of triglycerides, three groups of eight female Wistar rats were isocalorically fed for four weeks with either Vivonex, or Vivonex with 50% calorie substitution with an essential fatty acid mixture, or Vivonex with 50% calorie substitution with a saturated fatty acid mixture. Although Vivonex caused greater body weight gain, both essential fatty acids and saturated fatty acids increased small intestinal weight, mucosal weight, protein and DNA overall, and in each of three intestinal segments (proximal, middle and distal), compared with Vivonex. Mucosal indices were similar for essential fatty acids and saturated fatty acids. These results show that triglycerides, regardless of essential fatty acid content, are trophic to the rat small intestinal mucosa.

Animals↗

PubMed1981

[Effect of monovalent and bivalent cations and anions on the properties of ATPase from rabbit small intestine mucosa].

The effects of monovalent cations and anions on the ATPase activity of rabbit small intestine mucosa membranes was studied. It was shown that the small intestine mucosa contains the ATPase activity sensitive to NaCl and NaHCO3. This activity, in contrast to the HCO3--ATPase activity, is inhibited by ethacrinic acid, is practically insensitive to thyocyanate, has a pH optimum of 6.2, is unstable upon storage and is not inhibited by 2 mM EDTA. The catalytic and regulatory properties of HCO3--ATPase and NaCl/NaHCO3-stimulated ATPase were compared; their possible involvement in secretion in small intestine epithelium is discussed.

Adenosine Triphosphatases↗

PubMed1978

Hemorrhagic necrosis of the intestinal mucosa associated with disseminated intravascular coagulation.

Disseminated intravascular coagulation (DIC), experimentally induced by endotoxin, caused severe hemorrhagic necrosis of the intestinal mucosa in dogs. Microscopic observation showed tortuous thrombus formation in the microcirculation of the villi. Ligation of the pancreatic and bile ducts, or administration of heparin protected the mucosa from hemorrhagic necrosis, while systemic administration of tranexamic acid increased the intestinal mucosal lesion. Local pretreatment of the intestinal mucosa by Trasylol or tranexamic acid reduced the degree of hemorrhagic necrosis. It is concluded that intravascular coagulation in the microcirculation of the intestinal mucosa, as well as pancreatic proteases, play a role in the pathogenesis of hemorrhagic necrosis in the intestine associated with DIC.

Animals↗

PubMed1976

Purification of phosphodiesterase II from rat and guinea-pig intestinal mucosa.

Phosphodiesterase II from extracts of intestinal mucosa of rat and guinea pig was purified by chromatography on DEAE-cellulose, CM-cellulose and agarose. The rat enzyme was purified 350-550-fold, with recoveries ranging up to 46%. The best purification of the guinea-pig enzyme was 15-fold, and the recovery was only 2.6%, the large loss occurring during chromatography on DEAE-cellulose and agarose. The poor results with the guinea-pig enzyme reflect the difficulty in obtaining a truly soluble material. Repeated sonication of the crude guinea-pig preparations yielded material that was initially soluble but tended to re-aggregate quickly. Purification of the rat phosphodiesterase II increased its thermostability, the temperature of half-inactivation being increased from 54degrees to 60degreesC. Both enzymes had a Km value of 4 X 10(-5) M with thymidine 3'-(2,4-dinitrophenyl) phosphate as substrate and showed similar pH optima for activity. Both enzymes were inhibited slightly in 0.1 M-MgC12 or 2M-urea and much more strongly in 2M-(NH4)2SO4 or 6M-NaC1. The guinea-pig enzyme was usually inhibited more than the rat enzyme. The Arrhenius plots of the two enzymes differed slightly in slope, but both were biphasic, showing breaks between 30degrees and 40degreesC. It was concluded that the two enzymes were markedly similar in behaviour and that the differences found were related to the different degrees of purification attained by the procedures described.

Animals↗

PubMed1989

[Distribution of T cell subsets and DR antigen positive T cells in peripheral blood and in intestinal mucosa of inflammatory bowel disease].

The absolute number of T cell subsets and the rate of T cell DR antigen expression in the peripheral blood and the intestinal mucosa in IBD patients were compared with those in healthy normal controls by two color analysis. The methods used here were flow cytometry for the peripheral blood and immunohistological fluorescent staining for the intestinal mucosa. In peripheral blood lymphocyte (PBL), helper (CD4+ Leu8-) T cells increased in ulcerative colitis (UC), whereas suppressor (CD8+ CD11+) T cells decreased in Crohn's disease (CRD). In lamina propria lymphocyte (LPL) of intestinal mucosa, there were no changes in the proportion of T cell subsets in UC, whereas suppressor (CD8+ CD11+) T cells increased in inflamed mucosa of CRD. DR antigen positive T cells did not increase in PBL, but they increased in LPL of both UC and CRD. In conclusion, there are some differences in distribution of T cell subsets and DR antigen positive T cells between the peripheral blood and the intestinal mucosa in IBD patients. Moreover, the heterogeneity of the distribution of T cell subsets is observed between UC and CRD.

Adolescent↗

PubMed1983

Iron binding proteins of iron-absorbing rat intestinal mucosa.

The distribution and quantitation of the iron-binding proteins of rat small intestinal mucosa was studied, in iron-deficient and replete animals, to explore their role in the absorption of iron. Adsorption (mucosal uptake) of iron in in situ ligated loops of small intestinal mucosa was found to be uniform throughout the length of the small intestine whereas absorption (carcass uptake) showed a steep decreasing gradient from the duodenum to the ileum. The disrupted, in vivo labeled mucosal cells were fractionated by isopycnic centrifugation and transferrin and ferritin were quantitated by radioimmunoassay. Transferrin derived from mucosal cells was shown to have a higher affinity for the antibody than transferrin in serum. Of the transferrin present in the mucosal extract, only a portion could be accounted for by contamination from the serum; the proteolysis resistant and intrinsic transferrin may be mucosal cell specific. Transferrin was found in similar amounts in all regions of the small intestine, was not affected by iron loading but doubled in response to iron deficiency. Mucosal ferritin was found in greater amounts in the iron-absorbing areas of the intestine, increased in the duodenum of iron-loaded animals, and decreased in iron-deficient animals. The incorporation of newly absorbed radioiron into ferritin was only found in iron absorbing regions and was completely inhibited by colchicine and cytochalasin-B, suggesting that ferritin was loaded with iron at the point of iron absorption and that the process is associated with vesicle movement and not simple diffusion. Transferrin and ferritin-specific immunoabsorption and also gel filtration established that no other soluble iron binding proteins were involved in absorption.

Animals↗

PubMed2000

Fasting does not increase mRNA levels of proteolytic systems in small intestinal mucosa of the rat.

Fasting results in rapid and profound wasting of the small intestine. mRNA levels of genes encoding critical components of proteolytic systems were measured in small intestinal mucosa to indirectly assess the possible role that proteolysis plays in mediating this wasting. Male Sprague-Dawley rats (120 g; n = 6 per group) were either fed or fasted for 1 or 2 days. Small intestinal mucosal mass decreased by 19% and 31% after 1 and 2 days of fasting, respectively (P < 0.05). Fasting did not significantly change mRNA levels for lysosomal (cathepsin B) or ubiquitin-proteasome-dependent (ubiquitin, 14-kDa ubiquitin-conjugating-enzyme E2, and the C8 and C9 proteasome subunits) systems. Northern hybridizations were also performed using membranes made with poly A(+) mRNA instead of total RNA. mRNA levels for these proteolytic systems and m-calpain did not significantly change with fasting. These data clearly demonstrated that fasting does not increase expression of genes encoding critical components of proteolytic systems in the small intestinal mucosa, suggesting that increased proteolysis cannot explain wasting of the small intestinal mucosa during brief fasting in young rats.

Journal Article↗

PubMed1975

The cytological effects of infusion of luminal polyethylene glycol on the rat small intestinal mucosa.

An isolated sac of rat upper small intestine was prepared. Its lower end was drained to the skin. Solutions of known volume and composition were infused into the sac and the intestinal mucosa was examined by light and electron microscopy. Infusion of isosmotic (16.8 percent w/v) polyethylene glycol (PEG) resulted in prompt and progressively severe damage to enterocytes at the top of the villus, while goblet cells and basal-granulated cells were apparently unaffected. Thus, after 6-72 hrs a cap of goblet cells and basal-granulated cells accumulated at the tip of the villus, while the enterocytes underwent vacuolation and disintegration. Infusion of an isosmotic mixture of 1 percent PEG and 5.1 percent glucose caused no damage near the site of infusion, but damaged the intestinal sac further distally...

Animals↗

PubMed1986

Fe2+ uptake by mouse intestinal mucosa in vivo and by isolated intestinal brush-border membrane vesicles.

In vivo kinetics of mucosal uptake of luminal 59Fe2+ by tied segments of normal mouse duodenum are characterised by a Km of approx. 100 microM and a Vmax of approx. 9 pmol/min per mg wet weight of intestine. These values were determined at pH 7.25 in the presence of excess sodium ascorbate. Studies with luminal Fe2+ concentrations of 100 microM reveal: uptake is relatively independent of ascorbate: Fe ratio and luminal pH and uptake is potently inhibited by 1 mM Co2+ or Mn2+ and large luminal NaCl concentrations but not by Ca2+. 3 days of hypoxia (0.5 atmospheres) yields no significant increase in subsequent total mucosal uptake by in vivo tied segments while uptake is significantly reduced by semi-starvation. Quantitative comparison of in vivo mucosal uptake with subsequent determination of isolated brush-border membrane 59Fe2+ transport in individual mice reveals a positive correlation (P less than 0.01) between the two parameters. These results, in conjunction with studies of isolated mouse duodenal brush-border membrane (Simpson, R.J. and Peters, T.J. (1985) Biochim. Biophys. Acta, 814, 381-388 and (1986) Biochim. Biophys. Acta 856, 109-114) suggest that the Fe2+ transport properties of isolated brush-border membrane are quantitatively adequate to explain in vivo mucosal uptake in normal and hypoxic mice at Fe2+ concentrations up to 100 microM.

Animals↗

PubMed1985

Ultrastructure of the epithelial cells of the small intestinal villi, the surface epithelium of the large intestinal mucosa and some elements of the intestinal mucosal lamina propria in rats with acute uraemia.

Electron microscopic studies on the dynamics of changes in the epithelial cells and some elements of the intestinal mucosal lamina propria were performed on rats after bilateral high ureter ligation. Simultaneously, they were referred to blood serum biochemical and electrolyte disturbances. The ultrastructural changes indicate that as early as in the initial period of acute uraemia water-electrolyte disturbances become evident, which are still increasing. In the later period cell organelles alter and bacterial infection sets in. Ultrastructural abnormalities of the intestinal mucous membrane are increasing proportionally to biochemical and electrolyte disturbances of the blood serum.

Animals↗

PubMed1975

Changes in the bidirectional sodium flux across the intestinal mucosa in Crohn's disease.

Bidirectional sodium flux across the intestinal mucosa was measured in a group of 10 patients with Crohn's disease treated in the past by panproctocolectomy with ileostomy and compared with a similarly treated group of 11 patients with ulcerative colitis. All of them were in good health at the time of the study and a recent radiological examination of the small intestine was normal. A significant reduction in bidirectional sodium flux was found in those patients with Crohn's disease and suggests that the intestinal mucosa is involved to a greater extent than can be judged by radiological appearances alone. This adds weight to the concept that Crohn's diseases is a diffuse rather than a focal lesion of the gastrointestinal tract.

Colitis, Ulcerative↗

PubMed1983

[Deperoxidation of hydroperoxylinoleic acid by the intestinal mucosa].

In the presence of glutathione, a homogenate of rat intestinal mucosa transforms linoleic acid hydroperoxide (LOOH) into the corresponding alcohol (LOH). The Km of the enzyme involved (a glutathione peroxidase) is 5.7 x 10(-6) M. The specific activity, measured as generated LOH, was found to be 0.058 mumol/mg protein/min, six times lower than that of the liver. A mitochondrial supernatant of the mucosal homogenate had 1.5 times the activity of the initial homogenate. The reduction of 1 mol LOOH requires 2 mol glutathione. Besides this enzymatic deperoxidation, 5% of the LOOH was decomposed in both the intestinal mucosa and liver by a non-enzymatic pathway, probably involving the Fe3+ of the haemoproteins.

Animals↗

PubMed1990

[Histological findings of the small intestinal mucosa in rotavirus infections in infants and young children].

In a prospective study we performed small intestinal mucosal biopsies in 40 children with acute rotavirus diarrhoea. Biopsies were taken from these children between the 2nd to 10th day of acute phase. The children were at an age of less than 18 month. 95% of the patients had normal histological findings of the small intestinal mucosa. Only 2 children (5%) had well defined injuries of intestinal mucosa. Correlations were not found between clinical findings, morphological results and therapy. In one child with gastroenteritis and meningitis rotaviruses were found in cerebrospinal fluid. In 31.25% of all children rotavirus infection was acquired by a nosocomial infection. The treatment of rotavirus infection is symptomatic. Usually intestinal mucosal biopsy as a routine diagnostic method isn't recommended and it should be used only in intractable courses.

Biopsy↗