SEARCH · Search PubMed

Results for “Enterocytes”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 145 records · Page 8Linked to original sources

PubMedDate not supplied

Effect of an elemental vs a complex diet on L-citrulline production from L-arginine in rat isolated enterocytes.

BACKGROUND: L-Arginine and L-glutamine are highly metabolized by intestinal cells, leading to various metabolites, including L-citrulline, which is required for optimal growth. Elemental diets, used in clinical practice to treat growth failure and malnutrition, are very different from complex diets normally consumed. The aim of the present study was to assess the effects of an elemental diet compared with a complex diet on L-arginine metabolism in rat isolated enterocytes and its modulation by L-glutamine. METHODS: Rats were fed the elemental diet (group ED) or the control diet (group C) for 14 days. Villus enterocytes then were isolated, and metabolic capacities or enzyme activities were assessed. RESULTS: The incubation of enterocytes isolated from group C with 0.1 mmol/L L-[U-14C]-arginine led to the production of 125 +/- 25 pmol L-citrulline/10(6) cells per 30 minutes. This production showed a twofold increase in the presence of 2 mmol/L L-glutamine. In group ED, L-citrulline synthesis from L-arginine was markedly lower in the absence or in the presence of L-glutamine. This coincided with lower carbamoylphosphate synthase I activity and carbamoylphosphate (CP) content of enterocytes. Other L-arginine and L-glutamine metabolic pathways were not affected. Similar results were obtained when the elemental diet was administered continuously through a gastric catheter or fed by mouth. CONCLUSIONS: L-Glutamine favors the synthesis of L-citrulline from L-arginine in isolated enterocytes, probably via an increase in CP production. Changing the diet composition, from a complex to an elemental diet, results in an alteration of the enterocyte capacity to synthesize L-citrulline from L-arginine, irrespective of the rhythm of delivery.

Animals↗

PubMed1995

Susceptibility of porcine ileal enterocytes to the cytotoxin of Serpulina hyodysenteriae and the resolution of the epithelial lesions: an electron microscopic study.

The cytotoxin from Serpulina hyodysenteriae was injected into ileal loops of eight germ-free pigs, and the effects on the villi were observed after 1, 3, and 18 hours of exposure. The mature vacuolated villus enterocytes of the proximal part of the absorptive villi were most susceptible to the lethal effects of the cytotoxin and were extensively exfoliated. The enterocytes at the base of the villi, the goblet cells, and the follicle-associated epithelium of the dome villi, particularly the M cells, were less affected. As the enterocytes were shed, the villi progressively shortened and the basement membrane became extensively folded. The absorptive villi were markedly stunted at 3 hours, and flattened globlet cells predominated at the site of restitution of the lesion. The myofibroblasts were also damaged, apparently subsequent to the exfoliation of the enterocytes. There was no further damage at 18 hours. The absorptive villi were stunted and were devoid of the large interstitial spaces of the normal lamina propria; the enterocytes were generally columnar, and at the apex of each villus there was an accumulation of goblet cells. There was a preponderance of M cells at the apices of the dome villi. Restitution of the lesions was not as rapid as observed in in vitro systems. The changes observed indicated that as the proximal enterocytes of the absorptive villi were shed, the loss of hydrostatic forces in the lamina propria allowed the myofibroblasts to collapse the villi by progressively retracting the basement membrane. This reduced the surface area to be covered during restitution. Resolution of the lesions was still incomplete after 18 hours.

Animals↗

PubMed1998

Transport and metabolism of glucose in isolated enterocytes of the black bullhead ictalurus melas: effects of diet and hormones

The uptake and metabolism of glucose were assessed in enterocytes isolated from black bullhead Ictalurus melas. The objective of this study was to examine the effects of diet and hormone treatment on glucose transport and metabolism, so the enterocyte was the most appropriate preparation. Glucose transport was estimated using specific inhibitors: glucose uptake measured in the presence of phlorizin presumably represents transport at the basolateral membrane, whereas glucose uptake in the presence of cytochalasin B presumably represents transport at the brush border. Feeding bullheads a standard diet resulted in maximum enterocyte rates of glucose uptake of 438.2+/-35.5 nmol mg-1 cells h-1 for transport in the presence of cytochalasin B and 427.0+/-49.7 nmol mg-1 cells h-1 (means +/- s.e.m., N=12) for transport in the presence of phlorizin. These values represent 50 % of the total 3-O-methylglucose transported. The rate of transport in the presence of cytochalasin B was increased in bullheads fed a high-carbohydrate diet. Incubating bullhead enterocytes with glucagon or glucagon-like peptide-1 (GLP) at 10(-8 )mol l-1 and with dexamethasone or isoproterenol at 10(-6 )mol l-1 significantly increased the rate of brush-border transport, but not the apparent affinity constant (Kt). Activation was dependent on hormone concentration. In contrast, insulin was without effect on transport rates, nor did it counteract activation by glucagon-family peptides. CO2 production rates from d-[14C]glucose indicated that glucose metabolism was not limited by transport rates in the enterocytes. Glucagon and GLP decreased maximal oxidation rates, whereas dexamethasone, isoproterenol and insulin did not alter these rates. The activities of enterocyte hexokinase exceeded the rate of glucose oxidation but not the rate of transport of glucose, at least at maximum activities, implicating this enzyme as one component of the strategy to ensure that glucose is maximally available to the blood of this species.

Journal Article↗

PubMed1993

Macrophage-mediated enterocyte damage in BALB/c mice infected with different strains of Giardia lamblia.

The mechanism of mucosal injury in Giardia lamblia-infected animals and humans is not well understood, although the role of gut macrophages in killing the trophozoites is well known. It is speculated, however, that macrophage products have a role in tissue injury and inflammatory response during infection, as in other inflammatory diseases. Therefore, in the present study an attempt was made to examine the mechanism involved in enterocyte damage during giardiasis. This was achieved using co-culture of enterocytes and gut macrophages obtained from infected BALB/c mice. The extent of tissue damage was assessed by measuring the marker enzyme of enterocyte damage, lactate dehydrogenase. To investigate the role of the various proteases and free oxygen radicals released by activated macrophages on enterocyte damage, inhibitors of various proteases and free oxygen radicals were used. Superoxide radical and certain proteases were found to have important roles in bringing about enterocyte damage during this infection in mice. Parasite load, lactate dehydrogenase release, and extent of lipid peroxidation were more pronounced in mice infected with symptomatic strains than in asymptomatic ones. The theory of inflammatory cell-mediated enterocyte damage in Giardia lamblia infection is proposed.

Animals↗

PubMed1984

Uptake of vitamin B12 by isolated ileal enterocytes.

Isolated ileal enterocytes incubated with intrinsic factor-[57Co]vitamin B12 (IF-B12) at 37 degrees C took up 25 times more B12 than jejunal enterocytes. Uptake of B12 by ileal cells was dependent upon IF and Ca2+. B12 taken up by ileal enterocytes could be separated into two components: 1) B12 which was retained (E component) and 2) released (R-E component) by chelation of divalent cations. The E component could be removed from ileal cells by treatment with Triton X-100. Incubation of ileal enterocytes at 22 degrees C or with 2,4-dinitrophenol reduced incorporation of B12 into the E, but not the R-E, component. Ileal enterocytes were incubated with IF-[57Co]B12 washed and reincubated with unlabeled IF-B12. Reincubation resulted in a decrease in the amount of [57Co]B12 in the R-E component and a concomitant increase of that in the E component indicating that B12 was transferred from the R-E to the E component. Dinitrophenol reduced transfer from R-E to E components. These results suggest that, using isolated enterocytes, two sequential steps in ileal absorption of B12 can be identified: 1) energy-independent binding of IF-B12 to its receptor on the brush border followed by 2) an energy-dependent event which probably represents transfer of B12 from its receptor into the cell.

2,4-Dinitrophenol↗

PubMed1992

Two roles for transforming growth factor beta 1 in colon enterocytic cell differentiation.

The role of transforming growth factor beta 1 (TGF-beta 1) in enterocytic differentiation was examined by treating two undifferentiated HT29 colon carcinoma sublines, U4 and U9, with hexamethylene bisacetamide to up-regulate their level of TGF-beta 1 mRNA expression. Although both lines after treatment secreted approximately equal levels of biologically active TGF-beta 1, only U4H cells were found to undergo enterocytic differentiation when cultured postconfluence on collagen I-coated transwells, forming polarized monolayer cells with an apical brush border, whereas U9H cells remained multilayered and undifferentiated. Enterocytic U4H cells exhibited four times as much cell surface expression of the collagen I-binding protein alpha 2-integrin, twice as much of the accessory collagen-binding protein carcinoembryonic antigen, and almost twice as much binding to collagen I films as undifferentiated U9H cells. TGF-beta 1 treatment doubled U4 cell collagen I binding, increased expression of alpha 2-integrin 4-fold, but increased carcinoembryonic antigen expression only marginally. U4H cells displayed cell cycle regulation by arresting reversibly at a restriction point in G1 when placed in the postconfluent culture conditions which initiated enterocytic differentiation. In contrast, undifferentiated U9H cells exhibited no restriction point but arrested throughout G1. TGF-beta 1 blocked synchronized U4H cells in G1, whereas it stimulated the growth of U9H cells. Thus, TGF-beta 1 has two roles in enterocytic differentiation: to increase levels of collagen I adhesion proteins and to block enterocytic cells in G1 so that they can differentiate.

Acetamides↗

PubMed1992

Evolution of intestinal apolipoprotein B mRNA editing. Chicken apolipoprotein B mRNA is not edited, but chicken enterocytes contain in vitro editing enhancement factor(s).

Mammalian intestinal apolipoprotein B (apoB) messenger RNA (mRNA) undergoes posttranscriptional editing, changing codon 2153 from CAA in apoB100 mRNA to an in-frame translational stop codon (UAA) in apoB48 mRNA. By contrast, chicken intestinal apoB cDNA contains a CAA codon at the corresponding site and apoB mRNA from chicken enterocytes, kidney, and liver is unedited. The cDNA sequence of chicken apoB spanning the edited base is divergent from mammalian apoB cDNA sequence, with 70% homology over the conserved 29-nucleotide sequence (6662-6690) flanking codon 2153. Efficient in vitro editing of both human and rat, but not chicken, synthetic apoB RNA was achieved using rat enterocyte S-100 extracts. By contrast, chicken enterocyte S-100 extracts failed to edit chicken, rat, or human synthetic apoB RNA. Mixing experiments, however, revealed that chicken enterocyte S-100 extracts enhance the in vitro editing activity of rat, pig, and human enterocyte S-100 extracts upon homologous RNAs. The editing enhancement activity of chicken enterocyte S-100 extracts is tissue-specific, heat-sensitive, substrate-saturable, and sensitive to proteinase K, but resistant to micrococcal nuclease. The activity was partially purified by Q-Sepharose chromatography and has an average molecular mass of 49 kDa when analyzed by gel filtration chromatography. We conclude that the evolutionary adaptation of intestinal apoB mRNA editing requires both a requisite RNA motif and tissue-specific factors which mediate the site-specific modification.

Animals↗

PubMed1992

Regional variation in ontogeny of class II antigens in enterocytes of mouse small intestine.

The ontogeny of major histocompatibility class II antigens in small intestine enterocytes of postnatal C3H/He mice was investigated. Cryosections of duodenal, jejunal, and ileal segments from 7-, 14-, 16-, 20-, 21-, 23-, 25-, 27-, 28-day-old and 7-week-old mice were stained for the class II antigens with MRC OX6 monoclonal antibodies by peroxidase-antiperoxidase labelling. In adults, the duodenum exhibited least expression of class II antigens that increased progressively towards the ileum. The expression in the villous epithelium was first seen in the duodenum and jejunum 21 days after birth but the ileal enterocytes did not exhibit any class II antigens. The earliest appearance (21 days postnatal) of class II antigens in the enterocytes coincides with the age of weaning which suggests that immunologic stimulation by ingested antigens after weaning may influence expression of these antigens. At day 28 after birth, the duodenum and jejunum expressed levels comparable to those in the adults. The first expression of the antigens seen in the ileum was at day 28 postpartum. Crypt epithelium of the three regions of the small intestine showed expression similar to that of corresponding regional villous enterocytes. We conclude that there is an age-dependent regional variation in the expression of class II antigens in enterocytes, and the expression increases with age. The variation in expression of the class II antigens in enterocytes of postnatal mice is attributed to the developmental status of the tissue. The nature of postnatal expression of the antigens is important since an early appearance of these antigens may have implications in autoimmunity.

Aging↗

PubMed1991

Expression of MHC class II (Ia) antigen by the neonatal enterocyte: the effect of treatment with interferon-gamma.

Immunohistochemical techniques were used to probe the expression and inducibility of class II major histocompatibility complex (MHC) (Ia) antigens by the mouse enterocyte at various stages postpartum. Expression of Ia was related to both age and intestinal location. Ia antigen was not detected until at least 1 week post-weaning and was noted thereafter in both proximal and distal intestine. Both crypt and villus enterocytes were stained in the distal small intestine, but staining was restricted to the upper portion of the villus in the proximal small intestine. Moreover, the extent of staining and the intensity of staining were greater in the distal small intestine. The effect of a single injection of recombinant mouse interferon-gamma (IFN-gamma) on Ia expression by enterocytes of 16-day-old, suckling BDF1 mice was examined. Injection of distilled water (DW) or 1 to 2 x 10(4) U IFN-gamma did not induce enterocyte Ia expression. Doses of 4-10 x 10(4) U were effective inducers of Ia on crypt and, occasionally, on lower villus cells examined 24 hr later. Staining did not persist on the enterocyte beyond 48 hr. In conclusion, Ia is not normally expressed on small intestinal enterocytes of the mouse until after weaning; however, Ia expression can be induced earlier by treatment with IFN-gamma. It is not known whether failure to detect Ia expression prior to weaning reflects a lack of positive stimuli and/or the presence of inhibitory stimuli, possibly carried in the breast milk.

Aging↗

PubMed1991

[Factors intervening in the variations of in vitro adhesion power of enterotoxinogenic colibacillus (ETEC) to human enterocytes].

Human enterotoxigenic Escherichia coli adhere to the brush border of human enterocytes. The mean number of bacteria adhering to one enterocyte (adhesion index) varied from 0.5 to 3.1 when the strains produce adhesins. Different factors related to enterocytes and to bacteria are involved in this variability. The number of bacteria which adhered to enterocytes issued from the same donor varied from from 0 to 12. Moreover the proportion of enterocytes on which several bacteria sticked did not exceed 20%. This variability might be due to the disparity in the maturation of the enterocytes. On the other hand, whatever the adhesion factors considered, the adhesion index varied according to the donors. ETEC strains did not express adhesion when bacteria were grown in a liquid medium but this capacity could be restored after transfer on solid medium. This phenomenon seemed like a phase-variation and appeared to be linked to a 4 to 6 kilobases (kb) plasmid. On the other hand, when the bacteria were grown on agar medium (CFA-agar or Mueller-Hinton agar) two phenotypes of colonies could be observed: large colonies (LC) which were composed of non-adhesive bacteria and small colonies (SC) which were composed of a majority of adhesive bacteria; when the number of subcultures was not too great, a majority of colonies presented the small colonies phenotype. The plasmid content analysis showed the segregation of a high molecular weight plasmid DNA (approximately 100 kb) for the bacteria issued from large colonies phenotype.

Age Factors↗

PubMed1995

Fate of polarized membrane components and evidence for microvillus disassembly on migrating enterocytes during repair of native intestinal epithelium.

BACKGROUND: Maintenance of enterocyte polarity is crucial to normal intestinal function. Tight junctions and cell-matrix interactions play a role in maintaining polarized cell membrane domains. In many intestinal epithelial wounds, normal cell-cell associations mediated by tight junctions are lost. The goal of this study was to examine the fate of an apically restricted fucosylated glycoconjugate (FGC) and basolaterally restricted Na/K-ATPase in a model of intestinal epithelial repair. Comparisons are made to isolated enterocytes in which cell-matrix interactions are disrupted as well. EXPERIMENTAL DESIGN: We present a novel physiologically relevant model of intestinal epithelial injury and restitution that was used to examine the fate of two polarized membrane components by fluorescent and ultrastructural techniques. In addition, we used mechanical vibration to isolate enterocytes as individual and short sheets of cells from the intestinal basement membrane and evaluated the fate of these restricted membrane components using immuno- and lectin histochemistry. RESULTS: Na/K-ATPase maintained its basolateral membrane location in restituting epithelial but relocated to a nonbasolateral position in the majority of isolated enterocytes. The FGC maintained its apical restriction in isolated enterocytes and in epithelial cells migrating across denuded basement membrane. An additional and important observation noted in this study was a drastic alteration in shape of migrating epithelial cells characterized by diminution and loss of microvilli as the cells migrated across the injury. CONCLUSIONS: We conclude from our results that maintenance of Na/K-ATPase to a basolateral membrane position is influenced by cell-matrix interactions. In contrast, restriction of FGC to the apical membrane of enterocytes is dependent on the presence of microvilli and is not related to either cell-cell or cell-matrix interactions. Additionally, we suggest a new model of intestinal repair in which microvilli are disassembled. We speculate that membrane from disassembled microvilli, as well as lateral cell membrane, are used at the leading edge of the migrating cell.

Animals↗

PubMedDate not supplied

The 1994 Lindberg Award. The production of tumor necrosis factor, interleukin-1, interleukin-6, and prostaglandin E2 by isolated enterocytes and gut macrophages: effect of lipopolysaccharide and thermal injury.

Increasing evidence shows that cells other than immune cells have the potential for producing cytokines and arachidonate metabolites. It was the purpose of this study to determine whether isolated enterocytes could produce tumor necrosis factor, interleukin-1, interleukin-6, and prostaglandin E2, to compare the production with that of isolated gut macrophages, and to determine whether a difference existed in the production of these mediators after thermal injury. Guinea pigs received a 30% total body surface area burn and were killed 24 hours after injury. Isolated enterocytes and related intestinal macrophages (5 x 10(5) cells/ml) were cultured for 24 hours in the presence and absence of endotoxin, and the supernatants were assayed for the mediators. An increase was seen in production of interleukin-6 by enterocytes and by macrophages after thermal injury. In general enterocytes and gut macrophages produced about the same amounts of the different mediators. In contrast to macrophages from other tissues, enterocytes did not produce more prostaglandin E2 after stimulation with lipopolysaccharide, and with one exception gut macrophages did not produce larger amounts of mediators after stimulation with lipopolysaccharide. Enterocytes may be a significant source of immunomediator production and could contribute to the inflammatory response.

Animals↗

PubMed1996

Evidence for increased anionic arginase activity in pig enterocytes during development.

We have recently reported that the flux of L-arginine through arginase in enterocytes is increased in weaned pigs when compared with suckling animals (Blachier et al. 1993, Eur. J. Biochem. 216, 109-117). The aim of the present study was to characterize arginase activities at both stages of development. Enterocytes isolated from suckling animals were found to possess an anionic (50%) and a non-anionic (50%) form of arginase as judged from activities recovered from DEAE-cellulose ion exchange chromatography. In enterocytes isolated from weaned animals, anionic arginase was the major form representing 89% of arginase activity. This isoform is characterized by increased affinity for L-arginine (2 fold) and increased maximal velocity (39 fold) when compared with the anionic form originating from suckling piglet enterocytes. In conclusion, our data demonstrate that pig enterocytes are equipped with at least 2 isoforms of arginase and that anionic form of arginase activity appeared to be mainly responsible for the capacity of weaned pig enterocytes to catabolize L-arginine.

Animals↗

PubMed2004

Constitutive apical membrane recycling in Aplysia enterocytes.

In Aplysia californica enterocytes, alanine-stimulated Na+ absorption increases both apical membrane exocytosis and fractional capacitance (fCa; a measure of relative apical membrane surface area). These increases are thought to reduce membrane tension during periods of nutrient absorption that cause the enterocytes to swell osmotically. In the absence of alanine, exocytosis and fCa are constant. These findings imply equal rates of constitutive endocytosis and exocytosis and constitutive recycling of the apical plasma membrane. Thus, the purpose of this study was to confirm and determine the relative extent of constitutive apical membrane recycling in Aplysia enterocytes. Biotinylated lectins are commonly used to label plasma membranes and to investigate plasma membrane recycling. Of fourteen biotinylated lectins tested, biotinylated wheat germ agglutinin (bWGA) bound preferentially to the enterocytes apical surface. Therefore, we used bWGA, avidin D (which binds tightly to biotin), and the UV fluorophore 7-amino-4-methylcoumarin-3-acetic acid (AMCA)-conjugated avidin D to assess the extent of constitutive apical membrane recycling. A temperature-dependent (20 vs. 4 degrees C) experimental protocol employed the use of two tissues from each of five snails and resulted in a approximately 60% difference in apical surface fluorescence intensity. Because the extent of membrane recycling is proportional to the difference in surface fluorescence intensity, this difference reveals a relatively high rate of constitutive apical membrane recycling in Aplysia enterocytes.

Animals↗

PubMed2002

Lipopolysaccharide endotoxemia reduces cell proliferation and decreases enterocyte apopotosis during intestinal adaptation in a rat model of short-bowel syndrome.

Sepsis is frequently associated with or complicates short-bowel syndrome (SBS). To investigate the effects of lipopolysaccharide (LPS) endotoxemia on enterocyte proliferation and death via apoptosis in a rat model of SBS, adult male Sprague-Dawley rats were divided into three experimental groups: sham rats underwent bowel transection and reanastomosis; SBS rats underwent 75% small-bowel resection; and SBS-LPS rats underwent 75% bowel resection and were given intraperitoneal injections of LPS 10 mg/kg. Parameters of intestinal adaptation (bowel and mucosal weights, mucosal DNA and protein, villus height, and crypt depth), enterocyte proliferation, and death via apoptosis were determined on day 15 after the operation. Statistical analysis was determined by Student's and ANOVA tests with a P less than 0.05 considered significant. SBS-LPS animals demonstrated a significant decrease (vs SBS rats) in duodenal (20%), jejunal (30%), and ileal (15%) overall weight, duodenal (20%), jejunal (27%), and ileal (18%) mucosal weight, jejunal (20%) and ileal (30%) mucosal DNA, jejunal (29%) and ileal (31%) villus height, and jejunal (14%) and ileal (29%) crypt depth. LPS endotoxemia led to reduced cell proliferation and enterocyte apoptosis compared to untreated SBS animals. Thus, in a rat model of SBS, LPS endotoxemia inhibits intestinal adaptation. A possible mechanism may be decreased cell proliferation. Decreased enterocyte loss via apoptosis may reflect a reduced number of enterocytes. Other mechanisms (necrosis) may be mainly responsible for cell death following LPS injection.

Adaptation, Physiological↗

PubMed2005

Fatty acid utilisation and metabolism in caecal enterocytes of rainbow trout (Oncorhynchus mykiss) fed dietary fish or copepod oil.

A combined fatty acid metabolism assay was employed to determine fatty acid uptake and relative utilisation in enterocytes isolated from the pyloric caeca of rainbow trout. In addition, the effect of a diet high in long-chain monoenoic fatty alcohols present as wax esters in oil derived from Calanus finmarchicus, compared to a standard fish oil diet, on caecal enterocyte fatty acid metabolism was investigated. The diets were fed for 8 weeks before caecal enterocytes from each dietary group were isolated and incubated with [1-14C]fatty acids: 16:0, 18:1n-9, 18:2n-6, 18:3n-3, 20:1n-9, 20:4n-6, 20:5n-3, and 22:6n-3. Uptake was measured over 2 h with relative utilisation of different [1-14C]fatty acids calculated as a percentage of uptake. Differences in uptake were observed, with 18:1n-9 and 18:2n-6 showing the highest rates. Esterification into cellular lipids was highest with 16:0 and C18 fatty acids, accounting for over one-third of total uptake, through predominant incorporation in triacylglycerol (TAG). The overall utilisation of fatty acids in phospholipid synthesis was low, but highest with 16:0, the most prevalent fatty acid recovered in intracellular phosphatidylcholine (PC) and phosphatidylinositol (PI), although exported PC exhibited higher proportions of C20/C22 polyunsaturated fatty acids (PUFA). Other than 16:0, incorporation into PC and PI was highest with C20/C22 PUFA and 20:4n-6 respectively. Recovery of labelled 18:1n-9 in exported TAG was 3-fold greater than any other fatty acid which could be due to multiple esterification on the glycerol 'backbone' and/or increased export. Approximately 20-40% of fatty acids taken up were beta-oxidised, and was highest with 20:4n-6. Oxidation of 20:5n-3 and 22:6n-3 was also surprisingly high, although 22:6n-3 oxidation was mainly attributed to retroconversion to 20:5n-3. Metabolic modification of fatty acids by elongation-desaturation was generally low at <10% of [1-14C]fatty acid uptake. Dietary copepod oil had generally little effect on fatty acid metabolism in enterocytes, although it stimulated the elongation and desaturation of 16:0 and elongation of 18:1n-9, with radioactivity recovered in longer n-9 monoenes. The monoenoic fatty acid, 20:1n-9, abundant in copepod oil as the homologous alcohol, was poorly utilised with 80% of uptake remaining unesterified in the enterocyte. However, the fatty acid composition of pyloric caeca was not influenced by dietary copepod oil.

Animals↗

PubMed2004

Isolation and characterization of enterocytes along the intestinal tract of the gilthead seabream (Sparus aurata L.).

Epithelial cells were successfully isolated along the intestine of the gilthead seabream using a dissociation method based on intracellular-like solutions. Biochemical and physiological tests revealed highly viable cells from all intestinal segments. Image analysis was used to identify cell types in the epithelial preparations which were highly enriched in enterocytes (>95%) over mucous cells. Several digestive hydrolases were determined in the isolated cells. Maltase (M), sucrase (S), leucine aminopeptidase (LA), 5'nucleotidase (5'N), but not gamma-glutamyl transferase (gamma-GT) or alkaline phosphatase (AP) activities were found to be enriched in the epithelial preparations versus the corresponding intestinal homogenates. Comparison of digestive hydrolases revealed the existence of a clear heterogeneity in their expression pattern in the enterocytes, along the intestine. Na(+)-K(+)-ATPase, Na(+)-ATPase and Cl(-)-ATPase activities were also determined in the membrane fraction of isolated cells. Analyses of enzymatic profiles revealed a clear asymmetry in the distribution of all Mg(2+)-dependent ATPases; that is, maximal Na(+)-K(+)- and Na(+)-ATPase activities were observed in the enterocytes from pyloric caeca, while Cl(-)-ATPase activity was about twice as high in the enterocytes from anterior and posterior intestines compared with pyloric caeca. This is the first report demonstrating the existence of heterogeneous metabolic and enzymatic profiles in different enterocyte populations from euryhaline teleosts.

5'-Nucleotidase↗

PubMed2004

Effects of water temperature and diets containing palm oil on fatty acid desaturation and oxidation in hepatocytes and intestinal enterocytes of rainbow trout (Oncorhynchus mykiss).

Food grade fisheries have reached their sustainable limits while aquaculture production has increased to meet consumer demands. However, for growth in aquaculture to continue and utilise sustainable, feeding ingredients, alternatives to fish oil (FO), the predominant lipid component of fish diets, must be developed. Therefore, there is currently considerable interest in the regulation of fatty acid metabolism in fish in order to determine strategies for the best use of plant oils in diets for commercially important cultured fish species. Plant oils are characteristically rich in C18 polyunsaturated fatty acids (PUFA) but devoid of C20 and C22 highly unsaturated fatty acids (HUFA) found in FO. The fatty acyl desaturase enzyme activities involved in the biosynthesis of HUFA from PUFA are known to be under nutritional regulation and can be increased in fish fed diets rich in plant oils. However, fatty acid desaturase activity is also known to be modulated by water temperature in fish. The present study aimed to investigate the interaction between water temperature and diet in the regulation of fatty acid metabolism in rainbow trout. Trout, acclimatized to 7, 11 or 15 degrees C, were fed for 4 weeks on diets in which the FO was replaced in a graded manner by palm oil. At the end of the trial, fatty acyl desaturation/elongation and beta-oxidation activities were determined in isolated hepatocytes and intestinal enterocytes using [1-14C]18:3n-3 as substrate, and samples of liver were collected for analysis of lipid and fatty acid composition. The most obvious effect of temperature was that fatty acid desaturation/elongation and beta-oxidation were reduced in both hepatocytes and intestinal enterocytes from fish maintained at the highest water temperature (15 degrees C). There were differences between the two tissues with the highest desaturation/elongation and beta-oxidation activities tending to be in fish held at 11 degrees C in the case of hepatocytes, but 7 degrees C in enterocytes. Correlations between fatty acid metabolism and dietary palm oil were most clearly observed in desaturation/elongation activities in both hepatocytes and enterocytes at 11 degrees C. The highest beta-oxidation activities were generally observed in fish fed FO alone in both hepatocytes and enterocytes with palm oil having differential effects in the two cell types.

Animals↗