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PubMed1995

Leukotriene B4 and C4 metabolism in small intestine mucosa of children with celiac disease.

The enhanced generation of eicosanoids, including leukotrienes (LTs), may be involved in the pathophysiology of small intestine mucosal injury in patients with celiac disease. We investigated the metabolism of LTB4 and LTC4 by small intestine mucosa in patients with celiac disease by incubating biopsies of small intestine mucosa from patients and healthy subjects in media containing LTB4 and LTC4 and measuring the changes in LTB4 and cysteinyl LT concentrations in the incubation media. There was no significant degradation of LTB4 during a 60-min incubation of the small intestine mucosa from either children with celiac disease or controls. LTC4 was metabolized to LTD4 and LTE4 in a time-dependent manner by the small intestine mucosa of both patients and controls. However, the decreases in LTC4 and the increases in LTD4 and LTE4 by the intestinal mucosa from patients with celiac disease occurred more slowly than the changes observed in control experiments. Reduced catabolism of LTC4 in the small intestine mucosa due to villous atrophy may contribute to increased levels of LTC4 and may play an important role in the pathophysiology of celiac disease.

Biopsy↗
PubMed1982

A comparative study of cholesterogenic activities from acetate of neonatal chick liver, kidney and intestinal mucosa.

1. Acetate incorporation into nonsaponifiable lipids by liver and kidney slices and intestinal mucosa scrapes from neonatal chick was linear up to 100-150 mg of tissue. CO2 production from [1-14C]acetate was also studied as a function of weight of tissues. 2. Rate of acetate incorporation by the three mentioned tissues was essentially linear with respect to the incubation time assayed (0-120 min), CO2 production was also linear up to 60 min in kidney and 120 min in liver and intestinal mucosa. 3. In the conditions assayed the formation of nonsaponifiable lipids by liver slices reached constant values at acetate concentration of approximately 6 mM, while acetate incorporation by kidney and intestinal mucosa in the same conditions increased in nearly linear relationship to the concentration of available substrate. 4. Using the optimal assay conditions, acetate incorporation into nonsaponifiable lipids was maximal in neonatal chick liver, whereas kidney and intestinal mucosa only showed about 10% of the hepatic cholesterogenic activity. The percentage of acetate utilization for cholesterogenesis was also maximal in neonatal liver (about 10%). In the intestinal mucosa this percentage was also important (2-3%) being minimal in kidney slices (0.3%).

Acetates↗
PubMed1993

Characterization and distribution of alpha 2-adrenergic receptors in the human intestinal mucosa.

The subtype and the expression of the alpha 2-adrenergic receptor were investigated in the normal mucosa from human intestine by means of radioligand binding, RNase mapping, and measurement of adenylate cyclase activity. The study of the binding of the alpha 2-adrenergic antagonist, [3H]RX821002, to epithelial cell membranes indicated the existence of a single class of noninteracting sites displaying a high affinity for the radioligand (Kd = 1.1 +/- 0.5 nM). The rank order of potency of antagonists to inhibit [3H]RX821002 binding (RX821002 > yohimbine = rauwolscine > phentolamine approximately idazoxan >> chlorpromazine > prazosin) suggested that the receptor is of the alpha 2A subtype. A conclusion which is confirmed by the fact that only alpha 2C10 transcripts were found in the human intestine mucosa. Competition curves with (-)-norepinephrine demonstrated that 60% of the receptor population exhibited high affinity for agonists. This high-affinity state was abolished by the addition of GTP plus Na+ or by prior treatment of the membranes with pertussis toxin indicating it corresponded to G protein-coupled receptors. [32P]ADP-ribosylation and immunoblotting experiments identified two pertussis toxin-sensitive G proteins corresponding to Gi2 and Gi3. The study of the distribution of the receptor indicated that (a) the proximal colon is the intestine segment exhibiting the highest receptor density and (b) the receptor is predominantly expressed in crypts and is preferentially located in the basolateral membrane of the polarized cell. The distribution of the receptor along the crypt-surface axis of the colon mucosa can be correlated with a higher level of alpha 2C10-specific mRNA and a higher efficiency of UK14304 to inhibit adenylate cyclase in crypt cells.

Adenosine Diphosphate Ribose↗
PubMed2003

Insulin-like growth factor and insulin receptors in intestinal mucosa of neonatal calves.

Intestinal development is modified by age and nutrition, mediated in part by insulin-like growth factors (IGF-I, IGF-II) and insulin. We have investigated whether expression of IGF-I, IGF-II and insulin receptors (IGF-IR, IGF-IIR and IR; measured by real-time RT-PCR) and binding capacity (Bmax) of IGF-IR, IGF-IIR and IR in the mucosa of the small and large intestine of neonatal calves are modified by age and different feeding regimes. In experiment 1, pre-term (GrP) and full-term (GrN) calves (after 277 and 290 days of pregnancy respectively) were killed immediately after birth before being fed; a further group of full-term calves were fed for 7 days and killed on day 8 of life (GrC(1-3)). In experiment 2, full-term calves were killed on day 8 after being fed first-colostrum for 7 days (GrCmax), colostrum of the first six milkings for 3 days (GrC(1-3)) or milk-based formula for 3 days (GrF(1-3)). Intestinal sites differed with respect to expression levels of IGF-IR (duodenum>jejunum in GrC(1-3); ileum>colon, duodenum> or = jejunum in GrF(1-3)), IGF-IIR (colon>duodenum and ileum in GrN), and IR (lowest in ileum in GrP and CrN; highest in colon in GrC(1-3) and GrCmax). They also differed with respect to Bmax of IGF-IR (ileum and colon>duodenum and jejunum in GrP; ileum and colon>jejunum in GrN; colon>jejunum in GrC(1-3); lowest in jejunum in GrF(1-3)), IGF-IIR (duodenum and colon>jejunum and ileum in GrP; duodenum>ilem and colon>jejunum in GrN; duodenum, jejunum and colon>ileum in GrCmax, GrC(1-3), and GrF(1-3)) and IR (ileum>duodenum, jejunum and colon in GrCmax, GrC(1-3), and GrF(1-3)). There were significant differences between groups in the expression of IGF-IR (GrF(1-3)> GrCmax and GrC(1-3) in ileum), IGF-IIR (GrN>GrP and GrC(1-3) in colon; GrN>GrC(1-3) in jejunum and total intestine), and IR (GrCmax>GrF(1-3) in colon) and in the Bmax of IGF-IR (GrP>GrN in colon; GrCmax>GrF(1-3) in jejunum), IGF-IIR (GrN>GrP in duodenum, ileum and total intestine; GrN>GrC(1-3) in duodenum, ileum, colon and total intestine) and IR (GrN>GrP in total intestine; GrC(1-3)>GrN in ileum and total intestine). In addition, Bmax values of IGF-IR, IGF-IIR and IR were correlated with villus circumference, villus height/crypt depth and proliferation rate of crypt cells at various intestinal sites. There were marked differences in Bmax of IGF-IR, IGF-IIR and IR dependent on mRNA levels, indicating that differences in Bmax were the consequence of differences in posttranslational control and of receptor turnover rates. In conclusion IGF-IR, IGF-IIR and IR expressions and Bmax in intestinal mucosa were different at different intestinal sites and were variably affected by age, but not significantly affected by differences in nutrition. Receptor densities were selectively associated with intestinal mucosa growth.

Animals↗
PubMed1987

Ketone formation in the intestinal mucosa of infant rats.

The intestinal mucosa of infant rats was found to produce ketones when incubated in Krebs-Ringer-Bicarbonate solution. No production was found in weaned rats. Ketogenesis could be inhibited by D-carnitine or tetradecylglycidic acid (TDGA) an inhibitor of long-chain acylcarnitine transferase, suggesting that ketone production is due to a large extent to break-down of long-chain fatty acids. It is considered possible that both ketones and glucose (also produced by the infant mucosa) serve as substrates for the muscular part of the intestine.

Animals↗
PubMed2000

[Effect of rhubarb on oxygen radicals leakage from mitochondria of intestinal mucosa in burned rats].

OBJECTIVE: To investigate the effects of rhubarb on oxygen radicals leakage from the mitochondria of intestinal mucosa in burned rats. METHODS: The activity of cytochrome oxidase and superoxide dismutase (SOD) in mitochondria isolated from intestinal mucosa of burn model of rats was used to evaluate the oxygen radicals leakage from the mitochondria. And the SOD and malondialdehyde (MDA) levels in plasma, liver, intestinal mucosa and its mitochondria were also determined. RESULTS: After burn injury, the activity of cytochrome oxidase in intestinal mucosa decreased as the time elapses, rhubarb could improve it obviously. Furthermore, rhubarb could reduce the massive consumption of SOD and production of MDA obviously increased in plasma, liver, intestinal mucosa and its mitochondria after burning. CONCLUSION: Rhubarb could enhance the activity of cytochrome oxidase and SOD in small intestine mucosal epithelia in burned rats, thus the oxygen radicals leakage from the mitochondria to be reduced.

Animals↗
PubMed1991

[Purification and characterization of cytosol aminopeptidase from rat intestinal mucosa].

The isolation of cytosol aminopeptidase (CAP) from intestinal mucosa has involved difficult procedures because of low yield, instability of the enzyme and many other factors related to purification. The authors resolved these difficulties in the purification of the enzyme from intestinal mucosa of rats using hydrophobic chromatography on phenyl-TOYOPEARL 650S and ion exchange HPLC on Mono Q 5/5. In this procedure, a 60-fold purification was achieved and the purified enzyme revealed a single band with 56kDa molecular weight by SDS polyacrylamide gel electrophoresis. The purified enzyme preferentially hydrolyzed the Leucyl-containing peptides of Leu-Gly and Leu-Gly-Gly. However, it showed no activity on synthetic substrates of Leu-beta-naphthylamide, Gly-p-nitroanilide, Phe-p-nitroanilide or Met-beta-naphthylamide. The Km and Vmax for Leu-Gly were 0.91 mmol/l and 16.4 mol/min/mg protein, while for Leu-Gly-Gly they were 0.77 mmol/l and 20.6 mol/min/mg protein. The purified enzyme was heat-labile and quickly became less active in highly concentrated ammonium sulfate. The optimum pH was 6.5-10. The enzyme activity was stimulated by Mn2+ and Mg2+, while it was inhibited by EDTA, 1,10-phenanthroline, 2-mercaptoethanol and p-hydroxymercuribenzoate. The results suggested the participation of metal ions and the SH group in the enzyme activity. Furthermore the cytosol aminopeptidase was distinct from the brush-border membrane aminopeptidase in molecular weight, immunoreaction to cytosol aminopeptidase antiserum and the specificities to the substrates.

Aminopeptidases↗
PubMed1979

The mechanism of epithelial shedding after ischemic damage to the small intestinal mucosa. A light and electron microscopic investigation.

The intestinal mucosa of the rat was examined by light and electron microscopy 15, 30, 60 and 120 min after complete ligation of the vessel arcades of the proximal jejunum. The characteristic sign of ischemic damage to the small intestinal mucosa and the reason for epithelial shedding is the appearance of membrane enclosed cytoplasmic blebs which arise at the cell base of the enterocytes and detach the epithelium from the basement membrane. This process begins at the tip of the villi before the enterocytes display signs of irreversible damage and progress to the base of the villi with continuation of the ischemia.

Animals↗
PubMed1998

Radioprotection of the rat intestinal mucosa by tirilazad.

PURPOSE: To assess intestinal radioprotection by systemic or lumenal tirilazad mesylate and to test potential tumour radioprotection. MATERIALS AND METHODS: Segments of the mid small bowel were surgically exteriorized. Tirilazad was given either intravenously or intralumenally 30 min prior to 11 Gy of X-irradiation to the exteriorized intestine. Tissues were harvested 5 days later to measure crypts per circumference and mucosal height. Potential tumour protection was assessed in a mouse sarcoma model. Tumours implanted in the hind limb were allowed to grow until a standard volume was attained, then irradiated (10 Gy) 30 min after intravenous (i.v.) administration of saline or tirilazad. Tumour growth was recorded for the next 22 days to determine if pretreatment with tirilazad interfered with radiation effects. RESULTS: Systemic tirilazad provided no protection against intestinal damage and did not alter tumour growth after irradiation. Topical tirilazad yielded highly significant protection of intestinal mucosa. CONCLUSIONS: These preliminary observations showed that topical tirilazad diminished radiation enteritis. Systemic drug had no effect on the severity of damage to the intestine nor did it inhibit radiation effects on a tumour.

Animals↗
PubMed1984

Hydroxylation of prostaglandin A1 by the microsomes of rabbit intestinal mucosa.

Microsomes from rabbit small intestine mucosa were found to catalyze the hydroxylation of PGA1 in the presence of NADPH. The major product was identified as 20-hydroxy PGA1 by using high performance liquid chromatography and gas chromatography-mass spectrometry, and the minor product was assumed to be 19-hydroxy PGA1. The ratio of the former product to the latter was about 24.1. The specific PGA1 omega-hydroxylase activity of small intestine microsomes was comparable to that of liver microsomes, and was significantly higher than those of microsomes from other tissues such as kidney cortex and lung. Microsomes from rabbit colon mucosa also catalyzed the hydroxylation of PGA1 in the presence of NADPH, with the ratio of omega- to (omega-1)-hydroxy PGA1 formed being 33.0. The PGA1 hydroxylase activities of the microsomes from both small intestine and colon were inhibited markedly by carbon monoxide, indicating the participation of cytochrome P-450. A cytochrome P-450 was solubilized from small intestine microsomes, and purified to a specific content of 10.5 nmol of cytochrome P-450/mg of protein. This cytochrome hydroxylated PGA1 at the omega-position with a turnover rate of 38.2 nmol/min/nmol of cytochrome P-450 in the reconstituted system containing cytochrome P-450, NADPH-cytochrome P-450 reductase, cytochrome b5 and phosphatidylcholine. It is suggested that this cytochrome P-450 is specialized for the omega-hydroxylation of PGA1 in small intestine microsomes.

Animals↗
PubMed1987

Purification and separation of two soluble fucosyltransferase activities of small intestinal mucosa.

1. Rat small intestinal soluble fucosyltransferase is purified more than 2000-fold using chromatographic procedures with DEAE-cellulose, CM-cellulose, GDP-Sepharose and Concanavalin A-Sepharose. 2. Chromatography on Sephadex G15 of the final enzymatic fraction clearly separates two activities: a first peak incorporates fucose on asialoserotransferrin and a second peak on asialofetuin. 3. The use of small saccharidic acceptors (phenylgalactose, lactose, lacto-N-fucopentaose I) and the analysis of fucosylated asialoglycoproteins indicate that the first activity corresponds to an alpha-(3/4)-fucosyltransferase and the second one to an alpha-(1-2)-fucosyltransferase. 4. Protein analysis by polyacrylamide gel electrophoresis in the presence of SDS for each enzyme shows two bands corresponding to a mol. wt of about 65,000 and 70,000. The two enzymes have the same sensitivity to the action of N-ethylmaleimide.

Animals↗
PubMed1975

Substrate interactions on the intestinal mucosa: a concept for the regulation of intestinal digestion.

1. The hydrolysis of glycyl-L-leucine, glycyl-L-tyrosine, tributyrin, sucrose, maltose, soluble starch and alpha- and beta-glycerophosphates by everted segments of rat intestine was estimated separately or in combination. 2. A comparative study showed significant interaction between different substrates which affected their digestion. 3. Two types of interaction were identified: products of hydrolysis (1) affected the hydrolysis of homologous substances, e.g. methionine and alanine inhibited glycyl-L-leucine hydrolysis, maltose reduced glucoamylase (alpha-1,4-glucan glucohydrolase; EC 3-2-1-3) activity (intracatenary interactions); (2) interfered with the hydrolysis of a different group of substances, e.g. tributyrin inhibited dipeptidase (glycyl-L-leucine hydrolase; EC 3-4-3-2) and alkaline phosphatase (EC 3-1-3-1), glycyl-L-leucine interfered with the activity of the latter enzyme (intercatenary interactions). 4. Mechanisms of interactions were suggested by the results of a comparison of the extent of inhibition or activation of two enzymes (glycyl-L-leucine hydrolase and alkaline phosphatase) in situ in everted intestinal segments or after solubilization with papain or Triton X-100, and different treatments known to affect allosteric sites of these enzymes. 5. Tributyrin and dipeptides were found to act on alkaline phosphatase as allosteric regulators. A discontinuity of the Arrhenius plot suggested the existence of different enzyme conformations which were re-arranged by tributyrin. 6. Substrate interactions in digestion were found in adult rat, cat, rabbit and hen. Substantial differences were found between classes (Aves and Mammalia), orders (rodents, lagomorphs and carnivores) and between age-groups within an animal strain (in this instance, for the rat). 7. These interactions are thought to be involved in the co-ordination of digestion with intestinal absorption and to regulate the time and site of subsequent hydrolysis.

Alkaline Phosphatase↗