Ontogeny of the Na(+)-H+ exchanger in rat ileal basolateral membrane vesicles

This study was designed to examine the activity of the Na(+)-H+ exchanger across the basolateral membranes of the ileal enterocyte and its developmental pattern. The function of the Na(+)-H+ exchanger was studied using a well validated basolateral membrane vesicle technique. Na+ uptake represented transport into the vesicle rather than binding as validated by initial rate studies. Na+ uptake represented an electroneutral process as shown by studies in which negative membrane potential was induced by the ionophore valinomycin. Various outwardly directed pH gradients significantly stimulated Na+ uptake compared with no pH gradient conditions at all age groups. However, the magnitude of stimulation was significantly different between the age groups with more marked stimulation of amiloride-sensitive Na+ uptake occurring in adolescent rats as compared to weanling or suckling rats. The amiloride sensitivity of the pH stimulated Na+ uptake was investigated using [Amiloride] = 10(-2)-10(-5) M at pHi/pHo = 5.2/7.5. At 10(-2) M amiloride concentration, Na+ uptake was inhibited by 80%, 70%, 77%, in the basolateral membranes of adolescent, weanling and suckling rats, respectively. Dixon plot analysis in both adolescent and weanling rats was consistent with two amiloride binding sites, a low affinity system and a high affinity system. In the suckling rat, on the other hand, the data supported a single high affinity binding site. Kinetic studies revealed a Km for amiloride-sensitive Na+ uptake of 12.6 +/- 6.6, 10.2 +/- 1.77, 9.46 and Vmax of 4.83 +/- 1.22, 4.47 +/- 0.36 and 8.08 +/- 1.92 n.mol.mg.protein-1.7 s-1 in suckling, weanling and adolescent rats, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

The intestinal habitat for organized lymphoid tissues in ruminants; comparative aspects of structure, function and development

Unlike the Peyer's patches of rats and mice, which are considered to be secondary lymphoid organs, the ileal Peyer's patch of sheep is thought to be responsible for the primary generation of B cells, like the bursa of Fabricius of birds. The ileal Peyer's patch of sheep shows prenatal maturation, antigen-independent lymphopoiesis, a rate of lymphocyte production larger than that of the thymus, and involution at a young age. Follicles contain few T cells and have an IgM+, relatively immature B lymphocyte population, as judged by B-cell differentiation markers. The follicle-associated epithelium of the ileal Peyer's patch is of a special type that sheds carbonic anhydrase-rich, 50-nanometer membrane-bounded particles (carbonic anhydrase-reactive particles; CAP) into the intercellular spaces. The CAP filter into the follicle centre and are taken up by lymphocytes. They represent the epithelial (bursa-like) element in an otherwise mesenchymal stroma of reticular cells embedding the follicle lymphocytes. Transepithelial transport of macromolecules, with the formation of multivesicular body-like cytoplasmic vacuoles, appears to be the basis for CAP formation. The jejunal Peyer's patches are devoid of CAP, persist in the adult animal, contain M cells with clusters of B cells in the follicle-associated epithelium, and have many CD4+ lymphocytes in the follicles and in the interfollicular areas. Aggregates of lymphoid follicles in the large intestine resemble the jejunal Peyer's patches with respect to their lymphocyte population and the ileal Peyer's patch with respect to their follicle-associated epithelium.

Lactase expression is controlled differently in the jejunum and ileum during development in rats

This study shows the distribution of the messenger RNA for lactase-phlorizin hydrolase during postnatal development and along the longitudinal axis of the rat small intestine. At birth, this messenger RNA was present along the whole length of small intestine, and its concentration remained elevated during the suckling period despite the concomitant decrease in enzyme activity. At weaning, the amount of lactase messenger RNA dropped specifically in the distal ileum. This decrease in lactase messenger RNA was initiated at the ileocecal junction, progressed gradually towards the jejunum, and followed the decrease in lactase activity several days later. Starvation and refeeding were also found to cause modifications of lactase activity and messenger RNA expression that were prominent in the distal part of small intestine. These data support that posttranscriptional and pretranslational levels of regulation are required to define the spatial and temporal expression of lactase in the rat small intestine.

Catechol-O-methyltransferase and aromatic L-amino acid decarboxylase activities in human gastrointestinal tissues

Human gastrointestinal samples from the corpus, antrum, bulbus, jejunum and ileum were assayed for soluble and membrane-bound catechol-O-methyltransferase (COMT) and aromatic L-amino acid decarboxylase (AADC) activity in vitro. The mean soluble COMT activities with 3,4-dihydroxybenzoic acid (DBA) and 3,4-dihydroxyphenylalanine (L-DOPA) as substrate were 70-242 and 70-174 pmol/min mg, respectively. The membrane-bound COMT activities ranged from 33 to 60 pmol/min mg in the different parts of the intestine. The AADC activities, measured with L-DOPA as the substrate, increased from 114 pmol/min mg in the corpus to 3488 pmol/min mg in the jejunum. The affinity of the soluble COMT was approximately 20 times higher for DBA (Km 15-19 microM) than for L-DOPA (Km 300-600 microM). The Km-values for L-DOPA of AADC and COMT were of the same order of magnitude. The specific COMT inhibitors, nitecapone and OR-611, effectively inhibited in vitro the human intestinal COMT activity. Nanomolar concentrations caused 50% inhibition with both DBA and L-DOPA as substrate.

Effect of Hymenolepis nana on the mouse ileal mucosal cells: histochemical studies

Histochemical studies of the ileal mucosal cells of mice experimentally infected with H. nana revealed definite increase in mucous secretions indicating increased activity of the goblet cells in response to mucosal irritation. The activity of acid phosphatase was also increased representing a sort of defence mechanism against the attached worms. The activities of ATP-ase and NADH diaphorase enzymes were decreased indicating disturbance in the metabolic and transport processes and in the absorptive function of the intestinal epithelial cells.

Regulation of sialyltransferase activity in intestinal segments of rats

A differential distribution of sialyltransferase (ST) in different regions of intestine has been shown. Jejunum and ileum homogenates from rats showed almost exclusive presence of alpha-2-3 ST (to Gal in Gal beta-1-4GlcNAc and/or to Gal in Gal beta-1-3GalNAc). In contrast, colon homogenates showed the presence of both alpha-2-3 ST (as above) and alpha-2-6 ST. Incubation of intestinal slices in presence of heat-inactivated horse serum (HHS) showed a time- and temperature-dependent secretion of soluble ST into the medium. Both jejunum and ileum slices showed high rates of secretion of alpha-2-3 ST. Colon slices, though rich in alpha-2-6 ST, secreted only alpha-2-3 ST. Colchicine, an anti-mitotic drug, injected into rats caused about 10-fold increase of the serum ST level. Jejunum slices from colchicine-treated rats showed an increased secretion of alpha-2-6 ST, suggesting that intestine undergoes a change in the expression of normal secretion of alpha-2-3 ST to a secretion of alpha-2-6 ST. The secretion of ST from incubated intestinal slices was inhibited by heparin. Certain protein factors (anti-proteases) in HHS bind to heparin-sepharose column and these protein factors are responsible for causing the secretion of ST into the medium. It has also been found that a supernatant fraction of the colon homogenate activated ST. Gel chromatography on HPLC produced 3-4 protein fractions from the colon cytosol and one of this fraction bearing high molecular weight proteins produced the maximum activation of ST.(ABSTRACT TRUNCATED AT 250 WORDS)

Splenectomy influences endotoxin-induced bacterial translocation

To determine whether splenectomy affects the antibacterial defenses of the gut, experiments were performed using bacterial translocation (BT) as a marker of intestinal barrier failure. The incidence of BT was measured 8 days after splenectomy or sham-splenectomy in mice receiving or not receiving endotoxin (0.1 mg IP). Splenectomy does not appear to promote BT from the gut, since the incidence of bacterial translocation after splenectomy or sham-splenectomy (5%) were not different. A second experiment was performed to determine whether the resistance to endotoxin-induced BT was modified after splenectomy. The incidence of endotoxin-induced BT was 73% in the unoperated control group, 59% in the sham-splenectomy group, but 23% in the splenectomy group (p less than 0.002). Thus, splenectomy but not sham-splenectomy increased the resistance of otherwise healthy mice to endotoxin-induced BT.

[Characteristics of ATPase activity in the sarcolemma of longitudinal and circular muscles of the canine ileum]

The subcellular fraction enriched in sarcolemmal vesicles was isolated from the longitudinal muscle (LM) and the circular muscle (CM) of the canine ileum by sucrose density gradient centrifugation. Treatment of the LM and CM membranes with sodium dodecylsulfate (0.2 mg/kg protein) led to a 3-fold increase in Na,K-ATPase activity (up to 24 and 39 mumol Pi/mg protein/h, respectively) and to a 90-95% inactivation of Mg-ATPase which was 2 and 8 times (for the CM and the LM, respectively) more active than Na,K-ATPase in the untreated sarcolemma. A specific inhibition of Na,K-ATPase activity by acetylcholine (Ach) and serotonin (ST) was observed which could de blocked in the presence of muscarinic and serotonin receptor antagonists. Sensitivity of the enzyme to ST was more than one order of magnitude higher than to Ach (IC50 = 10(-8) vs 1.2 x 10(-7) M). The inhibition of Na,K-ATPase activity by the neurotransmitters was more pronounced in the LM membranes (30-40%) than in the CM ones (10-20%). These data indicate that cell membranes of the LM and CM differ both in specific ATPase activities and the responsiveness of Na,K-ATPase to the receptor-mediated effects of Ach and ST.

Basement membrane components stimulate epithelialization of intestinal defects in vivo

Subepithelial tissues have an important role in the structure and function of the intestinal epithelium. Basement membrane components (BMC) stimulate epithelial cell migration and differentiation in vitro. The aim of this study was to determine the effect of BMC and/or interstitial tissue collagen (type I) on the in vivo intestinal regenerative response to intestinal patching. Twenty rabbits had two 2 x 5 cm ileal defects patched with the serosal surface of adjacent caecum. Group 1 (n = 5) were controls; group 2 (n = 5), group 3 (n = 5) and group 4 (n = 5) had collagen, collagen plus BMC, and BMC respectively applied to the distal patched defect. Animals were killed at 7 d and evaluated grossly for epithelialization and contraction of the defects. Epithelial coverage was greatest in the distal patch of group 4 animals (62 +/- 9%) and was significantly greater than the group 4 proximal patch and control values (43 +/- 7 and 40 +/- 14%, P less than 0.05). Contraction was similar in all groups (38 +/- 5 to 45 +/- 5%). Crypt cell production rate, villus height, and disaccharidase activities were similar in all groups. BMC stimulated epithelialization via a local mechanism since only the distal patch was affected. Type I collagen did not stimulate epithelialization and inhibited the effect of BMC. Since crypt cell production rate was similar in all groups, the enhanced epithelialization seen with BMC is primarily due to increased cell migration.

Refeeding after starvation in the rat: comparative effects of lipids, proteins and carbohydrates on jejunal and ileal mucosal adaptation

To compare the tropic effect of different dietary nutrients on mucosal adaptation in the jejunum and ileum, adult rats were submitted to a 96-h period of starvation and refed isocaloric liquid diets (1.5 kcal ml-1) containing either protein (casein), carbohydrate (starch) or lipids. In the jejunum, 4 days of starvation caused mucosal hypoplasia, villus and crypt shortening and a decrease in the total activity of disaccharidases with the exception of lactase which was markedly enhanced. In contrast, mucosal hypoplasia was incomplete in the ileum which exhibited an increase in crypt depth and in the specific and total activities of disaccharidases and of aminopeptidase. Compared with protein and carbohydrates, lipids exerted the strongest stimulatory effect for mucosal regeneration. In the jejunum as well as in the ileum, mucosal mass parameters, villus length, crypt depth and lactase activity did reverse towards their initial value within 1-3 days of refeeding lipids, even though the animals received only one-third of their normal daily caloric intake. Our results indicate that the pattern of response to fasting differs between the proximal and distal small intestine, and that the intestinal changes induced by starvation are rapidly reversed by refeeding small amounts of a diet rich in fat.

Enzymes degrading bacterial chemotactic F-met peptides in human ileal and colonic mucosa

Bacterial chemotactic F-met peptides have been identified in culture supernatants of intestinal bacteria and in human faecal dialysates. These potent inflammatory agents could play a role in intestinal inflammatory disorders should they cross the epithelial barrier of the gut. We have identified mucosal peptidases which degrade F-met-leu-phe (FMLP) in ileal and colonic mucosal biopsies obtained at colonoscopy. A carboxypeptidase, inhibited by D-L-benzyl succinate (BzS), accounted for more than 60% of total FMLP-ase activity, other uncharacterized peptidases contributing the rest of the activity against the intact peptide. An F-met deformylase, inactive against di- and tri-peptides, cleaves released F-met completing the degradation. Total FMLP-ase, carboxypeptidase and F-met deformylase activities were measured in serial mucosal biopsies from 15 control patients undergoing colonoscopy for occult bleeding with negative findings and from 15 patients with ulcerative colitis (UC) and 10 with Crohn's disease (CD). Highest activities were found in terminal ileum and lowest in the rectum. Total FMLP-ase and carboxypeptidase activities were similar in controls and UC patients but were substantially reduced in CD, especially in the terminal ileum (controls 493 +/- 146 and 116 +/- 73 nmol/100 micrograms protein per h, respectively and CD 231 +/- 96 and 41 +/- 36 nmol/100 micrograms protein per h, respectively (P = 0.0018 and 0.015). F-met deformylase activities were similar in all groups. There was no correlation between enzyme activity and severity of inflammation. FMLP degrading peptidases probably contribute to the mucosal barrier of the gut in regions of high bacterial colonization, limiting intestinal absorption and inflammatory responses to these potent bacterial products in the intestinal lumen.

Effect of the microbial lactase (EC 3.2.1.23) activity in yoghurt on the intestinal absorption of lactose: an in vivo study in lactase-deficient humans

Breath hydrogen excretion was measured in eight lactase (EC 3.2.1.108)-deficient volunteers ingesting 18 g lactose in the form of milk, yoghurt and heated yoghurt. Total excess hydrogen excretion (area under curve) was significantly lower after yoghurt and heated yoghurt, than after milk: 103 (SE 29), 191 (SE 32), and 439 (SE 69) respectively (P less than 0.001). The oro-caecal transit time of fermentable components from yoghurt and heated yoghurt (mainly lactose) was longer than that from milk: 165 (SE 17), 206 (SE 19), v. 103 (SE 19) min (P less than 0.01). An intestinal perfusion technique was used in the same subjects after ingestion on two consecutive days of 18 g lactose in yoghurt and heated yoghurt. Significantly less lactose was recovered from the terminal ileum after yoghurt than after heated yoghurt meals: 1740 (SE 260) v. 2825 (SE 461) mg (P less than 0.05), and approximately one-fifth of the lactase activity contained in yoghurt reached the terminal ileum. These findings indicate that more than 90% of the lactose in yoghurt is digested in the small intestine of lactase-deficient subjects and suggest that both the lactase activity contained in the viable starter culture and a slow oro-caecal transit time are responsible for this excellent absorption.

Cell differentiation in intestinal adenomatosis of pigs studied by histochemistry of laminin and enzymes of epithelial and subepithelial tissue

The distribution of enzymes and laminin was examined in ileal tissue from pigs suffering from intestinal adenomatosis to reveal the nature of the lesion. A disruption of the normal and specific pattern of distribution was found. Thus, the normal ileal epithelium was characterised by brush border enzymes: alkaline phosphatase, magnesium-dependent adenosine triphosphatase (Mg-ATPase), fluoride resistant acid phosphatase and 5'-nucleotidase; enzymes of the basolateral border: Mg-ATPase; and cytoplasmic enzymes: beta-glucuronidase, non-specific esterase and acid phosphatase. Subepithelial fibroblasts seemed to be characterised by 5'-nucleotidase. Laminin was present as a continuous band under the surface and crypt epithelium, somewhat thicker in the former. In contrast, the branching proliferating crypts of intestinal adenomatosis largely lacked enzymes characteristic of both villus and crypt cells. Reactions for the subepithelial components, laminin and fibroblasts were also reduced. The deficient differentiation of the epithelial as well as subepithelial components in porcine intestinal adenomatosis distinguish the condition from crypt hyperplasia and indicate an adenoma-like character.

Effects of postweaning protein malnutrition on intestinal inositol phosphatase activities in normally weaned and neonatally undernourished rats

Postweaning protein malnutrition imposed on normally weaned or neonatally undernourished rats fed a low-protein diet induced retardation of body and small intestinal growth. A sparing effect on intestinal growth as compared to body growth was observed during protein malnutrition. Postweaning protein malnutrition in normally weaned rats resulted in a significant elevation of specific activities of inositol triphosphatase and phytase in duodenum and jejunum without affecting the activity in ileum. On the other hand, protein malnutrition imposed on neonatally undernourished rats resulted in a significant decrease of enzyme activities in small intestinal segments. These results suggest altered activity of intestinal inositol phosphatase in postweaning protein malnutrition with the direction of effects dependent on the neonatal nutritional status.

The effects of feeding a saturated fat-rich diet on enzymes of cholesterol metabolism in the liver, intestine and aorta of the hamster

The effects of two dietary treatments on parameters of cholesterol metabolism were studied. Hamsters were maintained on diets containing 2% (w/w) cholesterol or 20% (w/w) hydrogenated coconut oil for 4 weeks. Both diets induced a hypercholesterolaemia. The effects of the two treatments on hepatic and intestinal acyl-CoA:cholesterol acyltransferase activity and 3-hydroxy-3-methylglutaryl-CoA reductase activity were measured. As expected, cholesterol feeding stimulated cholesterol esterification and inhibited cholesterol synthesis. Saturated fat-feeding had no effect on cholesterol synthesis but markedly inhibited cholesterol esterification in both liver and intestine. The diet-induced hypercholesterolaemia was strongly correlated with an increase in acyl-CoA:cholesterol acyltransferase activity in the activity. In contrast, the hypercholesterolaemia induced by feeding either of the two diets tended to increase aortic uptake of cholesterol and hence acyl-CoA:cholesterol acyltransferase activity. We suggest that the changes in cholesterol esterification correlate well with the expected flux of cholesterol into each tissue.

Postheparin plasma diamine oxidase in health and intestinal disease

In animals, the distribution of the enzyme diamine oxidase is confined, almost exclusively, to the small bowel mucosa. In humans, plasma diamine oxidase is at or below assay detection limits but can be liberated into the circulation from binding sites in the intestine by i.v. heparin. Therefore, the authors wished to see if diamine oxidase could be released by a low and safe dose of heparin (5000 U) and if the resultant area under the concentration-time curve would provide a noninvasive marker of segmental intestinal disease. In 17 control subjects, the mean area under the curve (following administration of 5000 U i.v. heparin) was 35.9 +/- 5.0 (SEM) mU.L-1.2 h-1; in 6 individuals studied on two separate occasions, postheparin plasma diamine oxidase profiles were reproducible (r = 0.98; p less than 0.001). The longitudinal distribution of diamine oxidase in the gastrointestinal tract, measured in 12 gastric, 16 jejunal, 6 ileal, and 18 colonic biopsies, was similar in humans to that found in animals. In patients with normal peroral biopsies, there was a linear relationship between jejunal mucosal and postheparin plasma diamine oxidase activities (r = 0.84; p less than 0.01). The areas under the curve in controls were then compared with those in patients with segmental intestinal diseases: 21 with ileal disease with or without colonic Crohn's disease (10 unoperated and 11 with ileal resection), 7 with non-Crohn's ileal resection, 8 with ulcerative colitis, 10 with untreated and 7 with treated celiac disease (6 studied before and after a gluten-free diet), and 5 studied during total parenteral nutrition and again after resumption of oral feeding. The results in the 18 ileectomized patients were subdivided into those with major (arbitrarily greater than 75 cm) and minor (less than 75 cm) resections. Areas under the curve were markedly reduced in nonresected Crohn's patients (6.0 +/- 1.79 mU.L-1.2 h-1; p less than 0.001 vs. controls), correlating inversely, in a first-order relationship, with disease activity (r = 0.82; p less than 0.001) and returning toward normal in 4 patients achieving disease remission. Low areas under the curve in total parenteral nutrition patients (4.5 +/- 0.9; p less than 0.001) were also reversible on resumption of oral feeding. However, areas under the curve were not significantly lower in patients with limited ileal resection (less than or equal to 75 cm), with celiac disease (untreated and treated), or ulcerative colitis than in controls.(ABSTRACT TRUNCATED AT 400 WORDS)

Effect of acute Yersinia enterocolitica infection on small intestinal ultrastructure

The purpose of this study was to assess the jejunal and ileal brush border injury caused by Yersinia enterocolitica and to correlate these alterations with functional abnormalities. Weanling rabbits infected with 10(10) organisms of a human pathogenic Y. enterocolitica strain were compared with control and pair-fed, sham-treated animals. On day 6, infection resulted in a diffuse decrease in brush border enzyme activities in the small intestine and villus atrophy and crypt hyperplasia in the ileum. By day 14, ileal architecture and jejunal disaccharidases had returned to normal, but enzyme abnormalities persisted in the ileum. Ultrastructural studies showed decreased brush border surface area in the jejunum and ileum on day 6 and in the ileum on day 14 of infection. Abnormalities of brush border function caused by infection correlated with the changes in microvillus surface area. In pair-fed animals on day 6, brush border surface area was slightly decreased in the ileum but increased in the jejunum, suggesting that the brush border injury resulted from infection rather than from malnutrition alone. The findings indicate that Y. enterocolitica inflicts a diffuse brush border injury that is in keeping with the generalized defect in brush border enzyme activity and transport function.

[The effect of exogenous prostaglandins E1 and F2 alpha on the adenosine triphosphatase activity in the ileal mucosa of rats]

The influence of exogenous PG E1 and PG F2 alpha on the Na-K- and HCO3-ATPase activities was studied in the rat ileum mucosa pretreated for 3 days with the PG biosynthesis inhibitors: indometacin, dexason, vitamin E. The blockade of the PG biosynthesis increased the activity of both ATPases. Administration of PG E1 and PG F2 alpha inhibited the activity of HCO-3--ATPase and either did not affect the Na-K-ATPase activity (PG E1) or increased it (PG F2 alpha). The prostaglandins seem to participate in the electrolyte transport processes via the ATPase activity modulation.

Net fluid secretion and impaired villous function induced by colonization of the small intestine by nontoxigenic colonizing Escherichia coli

The role of colonizing bacteria in the small bowel in causing diarrhea remains unclear. We examined whether colonizing, nontoxigenic Escherichia coli could alter small bowel function by determining net water and electrolyte fluxes and sucrase activity in colonized and noncolonized ileal segments by using the reversible-ileal-tie adult rabbit model. Colonization of the ileum with nontoxigenic E. coli for greater than or equal to 72 h at greater than or equal to 10(4)/cm2 was associated with significant functional derangements, as follows: (i) overt liquid diarrhea in 50% of animals colonized at greater than 10(4)/cm2; (ii) reversal of normal net ileal absorption to net secretion of water, sodium, and chloride; and (iii) significant decrease in mucosal sucrase activity. We conclude that small bowel colonization by colonizing, nontoxigenic E. coli impairs water and electrolyte absorption and sucrase activity in the absence of recognized enterotoxin, cytotoxin, invasion, or effacement traits.

Amylolytic activity in the digestive tract of lambs during the first months after birth

Alpha-amylase activity in duodenal chymus and glucoamylase activity in homogenate and microvilli membranes of enterocytes from duodenum, jejunum and ileum of lambs at an age of 1, 7 and 23 days was studied. Alpha-amylase activity in duodenal chymus increases proportionally with increasing the age of lambs, at 7 and 23 days of age rising 2 and 3 times respectively compared to one-day age. Glucoamylase activity in homogenate and Microvilli membranes increases even at 7 day-age 3-6 times depending on the part of small intestine, then keeping on the whole the same level.

[The effect of indomethacin on the activity of Na+,K+- and HCO3--ATPases and prostaglandin levels in the rat ileum mucosa after exposure to cholera exotoxin]

Preadministration of indomethacin (10 mg/kg of rat body mass), 1 hr before choleraic toxin injection, removed the toxin inhibitory effect on activity of Na+, K(+)-ATPase and decreased distinctly its inhibitory action on HCO3(-)-ATPase. At the same time, the indomethacin premedication caused a decrease in content of prostaglandins PGE, 6-keto-PGF1 alpha and of thromboxane B2 as compared with the choleraic toxin effect and controls. The data obtained corroborate the hypothesis on antisecretory effect of indomethacin occurring via PG-dependent mechanism.

Antigen-induced mucosal damage and restitution in the small intestine of the immunized rat

Intestinal mucosal damage and restitution were examined following antigen-induced systemic anaphylaxis in Nippostrongylus brasiliensis immunized rats. The rats were injected intravenously with N. brasiliensis antigen or saline. At 60 min, morphological and biochemical parameters were determined in jejunum and ileum, and the epithelial permeability was assessed by measuring recovery of 51Cr-ethylenediaminetetraacetic acid in the blood after injecting it into a ligated segment. Antigen challenge resulted in significant abnormalities: (1) villus damage with sloughing of enterocytes; (2) decreased activities of brush border enzymes; (3) decreased levels of mucosal histamine and rat mast cell protease II (mast cell mediators), and (4) increased uptake of 51Cr-ethylenediaminetetraacetic acid. Progression of the injury was examined by taking consecutive biopsies at 15-min intervals for 60 min and then at 5 h. At 15 min, an abnormality was present in all sections which ranged from minor oedema and enterocyte detachment at villus tips to virtual complete destruction of the apical region. Restitution occurred by villus contraction with migration of the epithelium over the damaged regions. At 5 h, the epithelium had resealed, but the villi were significantly reduced in height.

Disaccharidases activity in the intestinal mucosa after methotrexate therapy

Disaccharidases activity in the intestinal mucosa samples of rats was examined after intragastric and intramuscular methotrexate therapy. Methotrexate was given on a twice a week schedule (1 mg/kg body weight). The animals were sacrificed after 2 weeks, 1 month, and 2 months of this therapy. A statistically significant but transient decrease of the lactase and maltase activity was found. The authors suggest studying the beneficial effect of low disaccharidase diet in the first period of methotrexate therapy in children treated with methotrexate.

Effects of starvation and difluoromethylornithine (DFMO) on diamine oxidase activity in rat ileum

Starvation and difluoromethylornithine (DFMO) administration have profound affects on intestinal proliferation, ornithine decarboxylase activity, and tissue polyamine levels. Diamine oxidase activity may play a role in the regulation of proliferation, and the activity of this enzyme may be influenced by ornithine decarboxylase activity. To determine if diamine oxidase is influenced by starvation and DFM administration, ileal diamine oxidase activities were determined on mucosal homogenates from five groups of rats: fed control, starved for 48 h, fed group receiving DFMO, a starved/refed group, and a starved/refed group receiving DMFO. The homogenates from starved rats were found to have decreased ornithine decarboxylase activity and increased diamine oxidase activity when compared to control values. The homogenates from the DFMO group also were found to have decreased ODC activity however, mucosal diamine oxidase activity was also decreased. Refeeding produced a dramatic increase in ornithine decarboxylase activity and a minimal change in diamine oxidase activity. The preservation of diamine oxidase activity during starvation implies a need for the enzyme not related to mucosal proliferation or digestion. However, in the fed state, diamine oxidase activity may be more dependent on ornithine decarboxylase activity or its reaction product putrescine.

Effect of aflatoxin B1 treatment in vivo on the in vitro activity of hepatic and extrahepatic glutathione S-transferase

The effect of aflatoxin B1 (AFB1) on the glutathione S-transferase activity (GST) and on non-protein thiol levels of different tissues was studied in adult male Wistar rats. Animals received a single dose of the toxin (100 or 500 micrograms/kg body wt., p.o.), and were studied 6 or 24 h after administration. GST was determined in liver, renal cortex, duodenum, jejunum-ileum and distal ileum, using 3 substrates: 1-chloro-2,4-dinitrobenzene (CDNB), trans-4-phenyl-3-buten-2-one (PBO) and 1,2-epoxyethylbenzene (STOX). The non-protein thiol content of all tissues tested increased with the lowest dose at 6 h, returning to normal values at 24 h, while the higher dose produced a significant decrease in reduced thiol levels at 6 h, returning to normal values at 24 h. AFB1 administration induced, independently of dose and tissue, total GST (CDNB) and epoxide-transferase activity (STOX) while A--C-type transferases (PBO) were inhibited. Almost all activities returned to normal values at 24 h. In cases of enzyme induction there was in general an increase in Vmax and a decrease in apparent Km. The opposite was seen in cases of inhibition. In conclusion, the results provide evidence that extrahepatic GST could be important in the overall process of detoxification of AFB1. The behavior seen in hepatic and extrahepatic tissues revealed the functions of catalysis (B-type transferases) and covalent bond formation, as well as inactivation by probable AFB1 metabolites (A--C-type transferases).