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PubMed2004

Enterocytin: A new specific enterocyte marker bearing a B30.2-like domain.

Enterocyte differentiation is correlated to the expression of specific proteins which only a few of them are identified. In this study, we characterize a new marker of enterocyte differentiation using monoclonal antibodies. We showed that small intestinal enterocytes specifically express a new 47 kDa protein named Enterocytin. Expression of this protein increase along the crypt-villus axis and it is concentrated in the terminal web, lateral plasma membrane domain, and nucleus membrane of mature enterocytes. A 1.8-kb cDNA of Enterocytin was isolated by expression cloning from a cDNA library of rabbit small intestine. The amino acid sequence obtained shows an N-terminal region with a coiled-coil structure and a B30.2-like domain in the C-terminus region. By co-transfection and immunoprecipitation procedures on Cos cells, it was observed that the coiled-coil domain is involved in the homodimerization of Enterocytin. In the human intestine, a similar 47 kDa protein was detected, exclusively in the small intestinal enterocytes. In addition, expression of this protein in Caco2 cells is correlated with the state of differentiation of these cells. The restricted expression of Enterocytin in the intestine and its localization in mature cells suggest that it may contribute to the differentiation processes and maintenance of the enterocytic polarity.

Amino Acid Sequence↗
PubMed2004

Differential rAAV2 transduction efficiencies and insulin secretion profiles in pure and co-culture models of human enteroendocrine L-cells and enterocytes.

BACKGROUND: Cell-based therapies for treating insulin-dependent diabetes (IDD) can provide a more physiologic regulation of blood glucose levels in a less invasive fashion than insulin injections. Previously, we developed an engineered human enteroendocrine L-cell model for regulated insulin release via recombinant adeno-associated virus serotype 2, or rAAV2, transduction. The aim of this study was to evaluate the efficiency and selectivity of rAAV2-mediated insulin gene delivery to enteroendocrine L-cells in co-culture with a prevailing number of enterocytes, which are the predominant cell type in intestinal epithelium. METHODS: We tested rAAV2 transduction in pure and co-culture models of human cell lines of enterocytes (Caco-2 and T84 cell lines) and enteroendocrine L-cells (NCI-H716 cell line). Non-viral, chemical-mediated transfection was used as a control. Transduced and transfected co-cultures were subjected to insulin secretion studies. RESULTS: In pure cultures, rAAV2 exhibited a low transduction efficiency towards both Caco-2 and T84 enterocytes, as opposed to a strong reporter expression in permissive NCI-H716 L-cells. In co-cultures of NCI-H716 L-cells and Caco-2 or T84 enterocytes, rAAV2 exhibited differential transduction efficiency with a strong preference towards NCI-H716 L-cells. The rAAV2-transduced co-culture achieved regulated insulin release against stimulation, whereas the chemically transfected co-culture failed to respond. CONCLUSIONS: This study demonstrated that rAAV2-mediated insulin gene transfer can differentiate human intestinal cell types in vitro, in particular enterocyte and enteroendocrine L-cell lines. We consider the AAV2 vector a useful tool in developing enteroendocrine L-cell-specific insulin gene delivery for IDD treatment, in terms of AAV2 avoiding enterocytes and targeting selectively L-cells.

Cell Line↗
PubMed2003

Role of heparan sulfate in interactions of Listeria monocytogenes with enterocytes.

Heparan sulfate is known to participate in binding a wide variety of microbes to mammalian cells, but few studies have focused on the enterocyte. Normal human colonic and small intestinal enterocytes, and cultured HT-29 (but not Caco-2) enterocytes, reacted prominently with antibodies specific for heparan sulfate and for the core protein of syndecan-1 (a heparan sulfate proteoglycan). The heparan sulfate analog, heparin, inhibited interactions of Listeria monocytogenes (adherence and internalization) with HT-29, but not Caco-2, enterocytes. Internalization of L. monocytogenes by HT-29 enterocytes was inhibited by heparan sulfate and to a lesser extent by chondroitin sulfate, but not by the non-sulfated glycosaminoglycan hyaluronic acid. Compared to plasmid control ARH-77 cells, adherence of L. monocytogenes, was increased using ARH-77 cells transfected with syndecan-1 cDNA. Heparin binding protein(s) on L. monocytogenes were confirmed using biotinylated heparin. To determine if these in vitro observations might have in vivo relevance, L. monocytogenes was preincubated with heparin and then orally inoculated into mice. Compared to L. monocytogenes not pretreated with heparin, L. monocytogenes pretreated with heparin was associated with decreased extraintestinal dissemination to the mesenteric lymph nodes and liver of orally inoculated mice. Thus, heparan sulfate (possibly as the heparan sulfate proteoglycan syndecan-1) appears to participate in interactions of L. monocytogenes with enterocytes.

Animals↗
PubMedDate not supplied

Extracellular matrix modulates enterocyte growth via downregulation of c-jun but is independent of p21 and p27 expression.

Regulation of the intestinal crypt-villus axis is multifactorial and involves growth factors and extracellular matrix composition. Laminin, a component of the enterocyte basement membrane, induces enterocyte differentiation and inhibits proliferation. To investigate the mechanism of this observation, we examined the expression of cell cycle modulators in enterocytes cultured on laminin. IEC-6 enterocytes were cultured on collagen I or laminin for 24 hours in media with serum followed by 48 hours of culture in serum-free media. Cells were then stimulated with epidermal growth factor, and RNA and protein were extracted before and up to 18 hours after stimulation. c-jun mRNA expression and p21 and p27 protein expression were analyzed. Expression of c-jun was inhibited in cells grown on laminin as compared to collagen I. Expression of p21 and p27 was no different between cells grown on laminin or collagen I. The mechanism of enterocyte growth inhibition mediated by laminin involves downregulation of c-jun expression. In contrast, p21 and p27 levels were unaffected by extracellular matrix indicating that the changes in expression of these cyclin-dependent kinase inhibitors do not contribute to the effect of laminin on enterocyte proliferation.

Animals↗
PubMed2000

Primary porcine enterocyte and hepatocyte cultures to study drug oxidation reactions.

1. Primary porcine hepatocytes and enterocytes were isolated and cultured in Williams' E medium for up to 10 days to investigate potential organ differences in the metabolism of the immunosuppressive compound tacrolimus (FK 506) and of two investigational drugs (KC11346 and KC12291). Using LC-MS (FK506) and HPLC-FL (KC 11346/12291) a number of metabolites with identical mass and/or identical retention time could be detected. 2. In the case of tacrolimus hepatocytes and enterocytes produced the same spectrum of metabolites, e.g. bisdemethyl-tacrolimus, demethyl-tacrolimus, demethyl-hydroxy-tacrolimus and hydroxy-tacrolimus, albeit at varying intensities. 3. Treatment of enterocyte cultures with dexamethasone increased the overall metabolite formation very significantly (up to 36 fold). 4. The metabolism of tacrolimus was also studied with preparations of insect cells, that express specifically high levels of individual human cytochrome P450 (CYP) isoenzymes. All metabolites could be generated with microsomal preparations specifically expressing CYP3A4, but hydroxy-tacrolimus was exclusively produced by CYP3A5. 5. In the case of the investigational drugs KC 11346 and KC 12291 only three metabolites were formed by cultured enterocytes whereas hepatocytes produced 10 and 20 metabolites, respectively. 6. When assessed at the protein level CYP1A and CYP3A were expressed in cultures of porcine enterocytes for up to 10 days but porcine hepatocytes expressed additionally CYP2C9/10. 7. In conclusion, primary enterocytes and hepatocytes can be successfully cultured for several days while maintaining mono-oxygenase activity and may therefore be used as a tool for studying intestinal and hepatic metabolism.

Animals↗
PubMed2005

Increased expression and function of integrins in enterocytes by endotoxin impairs epithelial restitution.

BACKGROUND & AIMS: Experimental necrotizing enterocolitis (NEC) is characterized by circulating endotoxin (lipopolysaccharide [LPS]) and impaired enterocyte migration. We hypothesized that LPS increases integrin function and cell-matrix adhesion, leading to impaired enterocyte migration in the pathogenesis of NEC. METHODS: NEC-like intestinal injury was induced in newborn rats by hypoxia/gavage feedings, and restitution was determined by assessing bromodeoxyuridine-labeled enterocytes along the crypt-villus axis. Newborn mice were injected with 5 mg/kg LPS. IEC-6 cells were treated with LPS +/- LY294002 or wortmannin, and beta 1- and alpha 3-integrins were assessed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and immunofluorescence. Beta 1-integrin function was determined by adherence of fibronectin beads to IEC-6 monolayers. Migration of IEC-6 cells into a scraped wound was measured by time-lapse microscopy. RESULTS: Newborn intestinal injury was associated with decreased intestinal restitution and increased alpha 3- and beta 1-integrin expression in the ileal mucosa, which also was observed after LPS injection. In IEC-6 cells, LPS caused an increase in the expression of alpha 3- and beta 1-integrins, a shift of beta 1-integrins from the cytoplasm to the plasma membrane and an increase in fibronectin bead adhesion during which beta 1-integrins accumulated underneath attached beads. These effects could be reversed with LY294002 or wortmannin, suggesting phosphatidylinositol-3-phosphate kinase (PI3K) dependence. The increased integrin-matrix adhesion by LPS led to an inhibition of enterocyte migration, which could be reversed by anti-beta 1-antibodies. CONCLUSIONS: Enterocyte migration is inhibited by LPS through increased expression and function of alpha 3- and beta 1-integrins. Modulation of enterocyte migration via integrins may provide novel insights into the pathogenesis of NEC, in which intestinal restitution is impaired.

Androstadienes↗
PubMed2002

Alterations in enterocyte proliferation and apoptosis accompany TPN-induced mucosal hypoplasia and IGF-I-induced hyperplasia in rats.

The mechanisms underlying nutrient regulation of intestinal cell turnover are poorly understood. The total parenteral nutrition (TPN) model allows examination of how eliminating the growth-promoting signals stimulated by luminal nutrients, without the confounding factor of malnutrition due to food deprivation, influences enterocyte renewal. Our objective was to determine the contribution of enterocyte proliferation and apoptosis to the mucosal hypoplasia induced by TPN and the mucosal hyperplasia induced by insulin-like growth factor-I (IGF-I). We investigated the composition and structure of the jejunum and associated changes in enterocyte proliferation and apoptosis in growing rats maintained exclusively with TPN for 7 d and concurrent treatment with IGF-I or vehicle for 6 d. TPN-induced hypoplasia, specific to the small bowel mucosa, was associated with reduced enterocyte proliferation and increased apoptosis throughout the crypt and bottom half of the villus. In contrast, the hyperplastic effect of IGF-I reflected increased enterocyte proliferation and decreased apoptosis, particularly in the stem cell zone. In summary, the ability of IGF-I to prevent or reverse the decreased enterocyte proliferation and increased apoptosis accompanying TPN-induced mucosal hypoplasia substantiates the role of growth factors in tissue regeneration and emphasizes the importance of the growth-promoting signals stimulated by luminal nutrients in maintaining intestinal integrity.

Animals↗
PubMed2002

Host-derived enterocytes in intestinal grafts.

Replacement of donor lymphoid tissue by lymphocytes of recipient origin is an established phenomenon in small bowel transplants. However, replacement of donor epithelial cells of bowel grafts by host cells has not been demonstrated. The objective of our study was to determine whether donor enterocytes are replaced by host-derived enterocytes in the intestinal allograft. Graft biopsy specimens, obtained from five human male recipients of female intestine, were examined for the presence of male enterocytes. The biopsies dated from 90 to 770 days posttransplant. Formalin-fixed 3-microm specimen sections were stained for X and Y chromosomes by fluorescent in situ hybridization technique. Fluorescent microscopy of the stained sections identified male enterocytes in four patients, with a percentage of male cells ranging from 0.09% to 0.26% of the total enterocyte mass. Using the fluorescent in situ hybridization technique, we demonstrated the presence of host-derived male (XY) enterocytes in the female intestinal graft.

Enterocytes↗
PubMed2006

An examination of the interplay between enterocyte-based metabolism and lymphatic drug transport in the rat.

The current study has examined whether drugs that are transported to the systemic circulation via the intestinal lymph (and therefore associate with lipoproteins within the enterocyte) are accessible to enterocyte-based metabolic processes. The impact of changes to the mass of lipid present within the enterocyte-based lymph lipid precursor pool (LLPP) on the extent of enterocyte-based drug metabolism has also been addressed. Low (5 mg oleic acid/h) or high [20 mg oleic acid/5.2 mg lyso-phosphatidylcholine/h] lipid dose formulations containing halofantrine (which is lymphatically transported and metabolized) or dichlorodiphenyltrichloroethane (DDT) (which is lymphatically transported and relatively metabolically inert) and radiolabeled oleic acid were infused into the duodenum of lymph duct-cannulated rats. After 5 h, drug and radiolabeled oleic acid were removed from the infusions, allowing calculation of the first order turnover rate constants describing drug and oleic acid transport from the LLPP into lymph from the washout profiles. In one group of animals, bolus doses of ketoconazole were also administered to inhibit cytochrome P450-based metabolism. The rate constant describing halofantrine transport from the LLPP into the lymph was lower than that of oleic acid, whereas these differences were abolished in the presence of ketoconazole. DDT and oleic acid exhibited similar turnover rate constants. The data therefore suggest that enterocyte-based metabolism removes halofantrine from the LLPP before transport into the lymph. Furthermore, enhancing the lymphatic transport of halofantrine by coadministration of larger quantities of lipid reduced the difference between the turnover rate constant for halofantrine and oleic acid and seemed to reduce the extent of enterocyte-based metabolism.

Algorithms↗
PubMed2002

Strain-dependent induction of enterocyte apoptosis by Giardia lamblia disrupts epithelial barrier function in a caspase-3-dependent manner.

We recently demonstrated that Giardia lamblia rearranges cytoskeletal proteins and reduces transepithelial electrical resistance. The effect of G. lamblia on enterocyte apoptosis is unknown, and a possible link between microbially induced enterocyte apoptosis and altered epithelial permeability has yet to be established. The aim of this study was to assess whether G. lamblia induces enterocyte apoptosis in duodenal epithelial monolayers and whether this effect increases epithelial permeability. Monolayers of nontransformed human duodenal epithelial cells were incubated with sonicated or live G. lamblia trophozoites (NF, S2, WB, or PB strains) for 8, 24, and 48 h. Cell cultures were assessed for apoptosis by Hoechst fluorescence staining, enzyme-linked immunosorbent assay for apoptotic nucleosomes, and electron microscopy. In separate experiments, monolayers were pretreated with or without 120 microM caspase-3 inhibitor (Z-DEVD-FMK) for 1 h and were assessed for production of apoptotic nucleosomes, tight junctional integrity (with fluorescent ZO-1 staining followed by confocal laser microscopy), and transepithelial permeability for fluorescein isothiocyanate-dextran. G. lamblia strains NF and S2, but not strains WB or PB, induced enterocyte apoptosis within the monolayers, and this effect was inhibited by Z-DEVD-FMK pretreatment. Using the G. lamblia NF isolate, additional experiments investigated the possible link between enterocyte apoptosis and altered epithelial permeability. G. lamblia NF disrupted tight junctional ZO-1 and increased epithelial permeability, but these effects were also prevented by pretreatment with the caspase-3 inhibitor. These findings indicate that strain-dependent induction of enterocyte apoptosis may contribute to the pathogenesis of giardiasis. This effect is responsible for a loss of epithelial barrier function by disrupting tight junctional ZO-1 and increasing permeability in a caspase-3-dependent manner.

Animals↗
PubMed2005

STa and cGMP stimulate CFTR translocation to the surface of villus enterocytes in rat jejunum and is regulated by protein kinase G.

The cystic fibrosis transmembrane conductance regulator (CFTR) is critical to cAMP- and cGMP-activated intestinal anion secretion and the pathogenesis of secretory diarrhea. Enterotoxins released by Vibrio cholerae (cholera toxin) and Escherichia coli (heat stable enterotoxin, or STa) activate intracellular cAMP and cGMP and signal CFTR on the apical plasma membrane of small intestinal enterocytes to elicit chloride and fluid secretion. cAMP activates PKA, whereas cGMP signals a cGMP-dependent protein kinase (cGKII) to phosphorylate CFTR in the intestine. In the jejunum, cAMP also regulates CFTR and fluid secretion by insertion of CFTR from subapical vesicles to the surface of enterocytes. It is unknown whether cGMP signaling or phosphorylation regulates the insertion of CFTR associated vesicles from the cytoplasm to the surface of enterocytes. We used STa, cell-permeant cGMP, and cAMP agonists in conjunction with PKG and PKA inhibitors, respectively, in rat jejunum to examine whether 1) cGMP and cGK II regulate the translocation of CFTR to the apical membrane and its relevance to fluid secretion, and 2) PKA regulates cAMP-dependent translocation of CFTR because this intestinal segment is a primary target for toxigenic diarrhea. STa and cGMP induced a greater than fourfold increase in surface CFTR in enterocytes in association with fluid secretion that was inhibited by PKG inhibitors. cAMP agonists induced a translocation of CFTR to the cell surface of enterocytes that was prevented by PKA inhibitors. We conclude that cAMP and cGMP-dependent phosphorylation regulates fluid secretion and CFTR trafficking to the surface of enterocytes in rat jejunum.

Animals↗
PubMed1999

Intestinal adaptation and enterocyte apoptosis following small bowel resection is p53 independent.

Adaptation following small bowel resection (SBR) signals enterocyte proliferation and apoptosis. Because p53-induced p21(waf1/cip1) may be important for apoptosis in many cells, we hypothesized that these genes are required for increased enterocyte apoptosis during adaptation. Male C57BL/6 (wild-type) or p53-null mice underwent 50% proximal SBR or sham operation (bowel transection-reanastomosis). Adaptation (DNA-protein content, villus height-crypt depth, enterocyte proliferation), appearance of apoptotic bodies, and p53 and p21(waf1/cip1) protein expression were measured in the ileum after 5 days. Adaptation was equivalent after SBR in both wild-type and p53-null mice as monitored by significantly increased ileal DNA-protein content, villus height, and enterocyte proliferation. The number of crypt apoptotic bodies increased significantly after SBR evenly in both wild-type and p53-null mice. In the p53-null mice, SBR substantially induced the expression of p21(waf1/cip1) protein in villus enterocytes. The p53-independent induction of p21(waf1/cip1) may account for the similar intestinal response to SBR between wild-type and p53-null mice. Intestinal adaptation and increased enterocyte apoptosis following intestinal resection occur via a p53-independent mechanism.

Adaptation, Physiological↗
PubMed2005

Cdx2 specifies the differentiation of morphological as well as functional absorptive enterocytes of the small intestine.

Many transcription factors are involved in the molecular control of intestinal epithelial cell differentiation. We report in this study that the transcription factor Cdx2 functions to define absorptive enterocytes during intestinal epithelial differentiation. Cdx2 is expressed in the villi of the normal small intestine. Intestinal metaplasia, which expresses Cdx2, occurs as a pathological condition in gastric mucosa. We have previously established Cdx2 transgenic mice expressing Cdx2 exclusively in the gastric epithelium. In this study using Cdx2 transgenic mice, we show that Cdx2 plays a key role in the differentiation of intestinal absorptive enterocytes. The gastric mucosa of Cdx2 transgenic mice was morphologically completely changed into intestinal metaplastic mucosa. Absorptive enterocytes had microvilli which were observed by electron microscope. The intestinal metaplastic mucosa of Cdx2 transgenic mice expressed sucrase and peptide transporter PepT1. Disaccharidase and leucine aminopeptidase activities were observed in the intestinal metaplastic mucosa. Glucose and amino acids were absorbed from Cdx2 transgenic mouse stomach with intestinal metaplasia. Finally we generated mice whose intestine was extensively excised. Cdx2 transgenic mice with intestinal metaplasia survived even after extensive intestinal excision. We successfully demonstrated that Cdx2 induced not only morphological but also functional absorptive enterocytes in the intestinal metaplastic mucosa in vivo. Our results suggest that Cdx2 is necessary and sufficient by itself to specify the development of intestinal absorptive enterocytes, whereas other factors which are expressed in the small intestine are not always necessary for the differentiation of functional absorptive enterocytes.

Amino Acids↗
PubMed1999

Role of tyrosine kinase, ODC, and p34cdc2 kinase and cyclin B-associated cdc2 in jejunal enterocyte proliferation, maturation, and exfoliation in diabetic and DFMO-treated rats.

BACKGROUND: Several signal transduction pathways involved in rapidly proliferating cells of the intestine are currently not well understood. In the jejunum, crypt enterocytes are constantly replicating, lower villi are maturing, and upper villi are constantly shed. Type I diabetes is associated with jejunal mucosal hyperplasia, and administration of diflouromethylornithine (DFMO), an irreversible inhibitor of ornithine decarboxylase (ODC), causes hypoplasia. Phosphorylation of proteins controls cellular proliferation and/or exfoliation. Cell division cycle kinase (p34cdc2) and cyclin B-associated p34cdc2 kinase regulate the cell cycle during the transition from G2-M phase. Our aims were to: 1) investigate the activities of tyrosine kinase, ODC, total p34cdc2 kinase, and cyclin B-associated p34cdc2 kinase and 2) phosphorylate proteins at tyrosine residues in jejunal upper villi, lower villi, and crypt enterocytes of DFMO-treated control and diabetic rats. METHODS: Diabetes was induced by streptozotocin. DFMO was administered in drinking water in both control and diabetic groups for 10 days after the induction of diabetes. Jejunal enterocytes were isolated and kept frozen at -70 degrees C until ready to process. RESULTS: Diabetic rats showed jejunal mucosal hyperplasia as indicated by increases in the jejunal mucosal weight/cm and DNA content compared to control rats. Diabetic crypt enterocytes showed significant increases in activities of tyrosine kinase, ODC, total p34cdc2 kinase, and cyclin B-associated cdc2 as well as increased phosphorylation of proteins at tyrosine residues compared to control rats. DFMO prevented diabetes-induced jejunal hyperplasia, and decreased the activities of these enzymes and phosphorylation of proteins at tyrosine residues in both diabetic and control rats. Phosphorylation of a 14 kd protein became prominent in crypt, upper villi, and lower villi enterocytes of DFMO-treated diabetic and control groups. CONCLUSION: Diabetic jejunal mucosal hyperplasia appears to involve activation of complex signal transduction pathways such as tyrosine kinase, ODC, p34cdc2 kinase, and cyclin B. These enzymes are involved in proliferation and/or exfoliation of jejunal enterocytes. Our results also suggest that tyrosine phosphorylation of a 14 kd protein may be involved in cell exfoliation and that jejunal mucosal hypoplasia may be a synergistic effect caused by down regulation of the above enzymes.

Animals↗
PubMed2000

Intracellular events in the assembly of chylomicrons in rabbit enterocytes.

The aim of this study was to determine the intracellular events in chylomicron assembly in adult villus enterocytes. We have used novel methods for separation of the intracellular components of the secretory compartment [rough and smooth endoplasmic reticulum (RER and SER, respectively) and Golgi], and their membrane and luminal components, from villus enterocytes isolated from rabbit small intestine. The steady state composition of the components of the secretory compartment and the intracellular pools of newly synthesized apolipoprotein B-48 (apoB-48) and triacylglycerol (TAG) was determined. The observations indicate that the SER is the main site of TAG synthesis and of chylomicron assembly. Newly synthesized apoB-48 and TAG accumulate in the SER membrane and are transferred into the lumen in a microsomal triglyceride transfer protein-dependent step. In enterocytes isolated from chow-fed rabbits, in which fat absorption is relatively slow, transfer of apoB-48 and TAG from the SER membrane into the lumen appears to be rate limiting. In enterocytes from fat-fed rabbits, TAG accumulates in the lumen of the SER, suggesting that movement out of the SER lumen becomes rate limiting, when chylomicron secretion is markedly stimulated. In these cells, the cytosolic TAG also increased to 450 microgram/g enterocytes, compared with 12 microgram/g enterocytes from chow-fed rabbits, indicating that transfer of TAG from the SER membrane into the secretory pathway can become saturated, so that newly synthesized TAG moves into the cytosol.

Animals↗
PubMed1995

Ultrastructural and time-lapse observations of intraepithelial lymphocytes in the small intestine of the guinea pig: their possible role in the removal of effete enterocytes.

In previous ultrastructural studies we have shown that at the tip of intestinal villi in guinea pigs, effete enterocytes are separated into two portions: a thin apical cytoplasm to be exfoliated into the lumen and a major basal portion to be ingested by lamina propria macrophages. During this process, intraepithelially disposed, large granular lymphocytes interdigitate with enterocytes in a complex manner. In the present study, the relation between the enterocytes and the lymphocytes in the villous epithelium of the guinea pig small intestine is described by use of transmission and scanning electron microscopy in an attempt to visualize the roles and activities of the lymphocytes more clearly. The lymphocytes project numerous pointed processes into effete enterocytes, even piercing them. Enterocytes are deeply indented or perforated, probably as a result of the encroaching lymphocyte processes. Some enterocytes are separated into apical and basal portions by numerous large excavations in the cytoplasm. These findings indicate that repeated perforating penetration of the lymphocytes induces cell cleavage. Supporting this supposition, our microcinematographic observations demonstrate the alternate protrusion and withdrawal of processes of lymphocytes. The processes advance with a pointed end, and subsequently, retract with a rounded end in a cycle of 8-18 seconds.

Animals↗
PubMed1989

Changes in Na,K-ATPase, sodium ion, and glucose transport in isolated enterocytes in an experimental model of malabsorption.

Nippostrongylus brasiliensis infection of the rat resulted, at day 10 of infection, in decreased levels of jejunal enterocyte sodium-potassium-activated adenosine triphosphatase (Na,K-ATPase) and potassium-activated p-nitrophenyl phosphatase (K-pNPPase) activities. Parallel decreases occurred in active sodium efflux from jejunal enterocytes in the presence and absence of actively transported monosaccharides. Ileal enterocyte Na,K-ATPase and K-pNPPase activities were significantly increased, as was active sodium efflux. In contrast to controls, the presence of monosaccharides produced a stimulation of active sodium efflux from ileal enterocytes derived from infected rats. Enzyme and sodium transport changes in the jejunal enterocytes probably reflect cellular immaturity. Functional changes in ileal enterocytes probably represent a compensatory phenomenon.

Animals↗
PubMed1998

Ca2+ uptake through voltage-gated L-type Ca2+ channels by polarized enterocytes from Atlantic cod Gadus morhua.

The presence and localization of voltage-gated Ca2+ channels of L-type were investigated in intestinal cells of the Atlantic cod. Enterocytes were loaded with the fluorescent Ca2+ probe, fure-2/AM and changes in intracellular Ca2+ concentrations ([Ca2+]i) were measured, in cell suspensions, in the presence of high potassium levels (100 mm), BAY K-8644 (5 microM), nifedipine (5 microM) or omega-conotoxin (1 microM). L-type Ca2+ channels were visualized on intestinal sections using the fluorescent dihydropyridine (-)-STBodipy. Depolarization of the plasma membrane produced a rapid (within 5 sec) and transient (at basal levels after 21 sec) increase in [Ca2+]i. BAY K-8644 increased the [Ca2+]i by 7.2%. Cells in a Ca2+-free buffer increased [Ca2+]i after addition of 10 mm Ca2+, and this increase was abolished by nifedipine in both depolarizing and normal medium but not by omega-conotoxin. Single cell experiments using video microscopy revealed that enterocytes remained polarized several hours after preparation and that the Ca2+ entry and extrusion occurred at specific and different regions of the enterocyte outer membrane. Fluorescent staining of L-type Ca2+ channels in the intestinal mucosa showed the most intense staining at the brushborder membrane. These results demonstrate the presence of voltage gated L-type Ca2+ channels in enterocytes from the Atlantic cod. The channels are mainly located at the apical side of the cells, and there is a polarized uptake of Ca2+ into the enterocytes. This suggests that the L-type Ca2+ channels are involved in the transcellular Ca2+ entry into the enterocytes.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗