Nickel absorption and distribution from rat small intestine In situ

The aim of this work was to study the absorption of nickel chloride in rats by means of the intestinal perfusion in situ technique at nickel concentrations of 1, 5, 10, 25, and 100 mg/L. Active transport and facilitated diffusion seem to play an important role in the intestinal absorption of nickel at concentrations≤10 mg/L. At higher concentrations, the absorption rate would be limited by saturation of the carriers. The distribution of the absorbed nickel was studied by intestinal perfusion of a 10-mg Ni/L solution for 30 or 60 min. Both in concentration and amount, the jejunum showed the higher values of absorbed nickel, followed by the kidneys and liver. When all of the collected organs (brain, heart, liver, lungs, spleen, kidneys, and testicles) and blood, but not the small intestine, are analyzed following a 60-min perfusion, it was found that 1% of the initial concentration had passed through the intestinal barrier.     

A new role for enteric glucagon-37: acute stimulation of glucose absorption in rat small intestine

Glucagon-37 is secreted by intestinal L-cells following carbohydrate uptake. It is known to inhibit gastric acid secretion (hence also named oxyntomodulin) and appears to increase intracellular cyclic AMP concentrations. Since cyclic AMP could enhance intestinal glucose absorption, a possible stimulatory effect of glucagon-37 on glucose transport was examined. Glucagon-37 acutely increased glucose absorption in the isolated, vascularly perfused small intestine and in isolated enterocytes of the rat. In these cells the stimulation by glucagon-37 could be completely blocked by the cAMP antagonist Rp-cAMPS and was therefore mediated by cAMP. The stimulation of intestinal glucose absorption by glucagon-37 appears to be a major new physiological function.     

Developmental control of the expression of two ten-sugar branched chain fucolipids in rat small intestine

Two branched decaglycosylceramides, apparently identical to those identified in the small intestine of adult rats [Breimer ME, Falk K-E, Hansson GC, Karlsson K-A (1982) J Biol Chem 257:50–59], were absent during the three weeks following birth. They appeared abruptly at around 21 days. After their appearance, their tissue concentration and their base composition did not change during development. Their fatty acids were non-hydroxylated and the percentage of C₂₂–C₂₄ fatty acids, which was low at 24 days, increased and reached 48.6% by 27 days.Nomenclature Gal1-4Gal1-4GlcCer Globotriaosylceramide (GbOse₃Cer) - Il³NeuAc-LacCer M_M3-ganglioside - GalNAc1-3Gal1-4Gal1-4GlcCer globoside (globotetraosylceramide, GbOse₄Cer)     

Evaluation of role of the peptide transport system in absorption of dipeptides in the rat small intestine in chronic experiments <Emphasis Type="Italic">in vivo</Emphasis>

Hydrolysis and absorption of glycylglycine and glycyl-L-leucine as well as absorption of glycine and leucine were studied in chronic experiments on rats with their isolated small intestine loop. Values of the “true” kinetic constants (with taking into account effect of the preepithelial layer) were determined to be as follows: (1) K _t = 46.7 ± 4.0 and 2.15 ± 0.59 mM, J _max = 0.74 ± 0.15 and 0.16 ± 0.03 μmol min^?1 cm^?1 (for transport of free glycine and leucine, respectively); (2) K _t = 4.4 ± 0.6 and 4.8 ± 0.9 mM, J _max = 0.24 ± 0.02 and 0.23 ± 0.02 μmol min^?1 cm^?1 (for transport of glycylglycine and glycyl-L-leucine, respectively); (3) K _M = 5.4 ± 1.0 and 38.2 ± 4.4 mM, V _max = 0.09 ± 0.02 and 0.24 ± 0.07 μmol min^?1 cm^?1 (for membrane hydrolysis of these dipeptides, respectively). According to our calculations, in the wide range of the initial glycylglycine concentrations (2.5–40 mM) a part of the peptide component in its total absorption accounts for 0.77–0.80. In the case of glycyl-L-leucine a part of the peptide component in the total glycine absorption decreases from 0.89 to 0.84, while in the total leucine absorption—from 0.86 to 0.71, the initial dipeptide concentration rising from 5 to 40 mM. The obtained results show that the peptide component prevails in absorption of the studied dipeptides in the rat small intestine, but its role is much lesser than what many authors believe. In the case of glycyl-L-leucine, the peptide component can achieve saturation in the range of high substrate concentrations, its part decreasing essentially to become compared with absorption of free amino acids formed as a result of the dipeptide membrane hydrolysis.     

Increased zinc absorption but not secretion in the small intestine of metallothionein-null mice

Metallothionein (MT) has been assigned a role in intestinal Zn absorption and secretion. The influence of MT was investigated in isolated segments of the small intestine from mice lacking the expression of MT I and II genes (MT−/−). To measure Zn absorption, washed 10- to 12-cm segments of the proximal and distal small intestine of MT−/− and control MT+/+ mice were filled with ⁶⁵Zn as ZnSO₄ (10 μg/mL), and the amount of ⁶⁵Zn appearing in the external buffer was measured over 4 h. To measure Zn secretion, the same procedure was followed using everted gut segments. The ⁶⁵Zn absorption from the small intestine was significantly greater in MT−/− mice, but only in the absence of albumin. In the proximal small intestine, the inclusion of 2% albumin in the external buffer significantly increased Zn absorption from 6.8% (no albumin) to 13.2% (with albumin) for MT−/−, and from 4.9% (no albumin) to 14.2% (with albumin) for MT+/+. In the distal segment, the respective values, with and without albumin respectively were 9.5% and 15.1% for MT−/− mice and 4.3% and 16.1% for MT+/+ mice. Regarding ⁶⁵Zn secretion, there was no difference between MT+/+ and MT−/− in either segment. However, the rate of secretion was higher in the proximal small intestine for both genotypes. Although it can be demonstrated that MT limits Zn absorption under controlled conditions in vitro, the ability of albumin to overcome this effect emphasizes the importance of circulating ligands in Zn transport.     

Uptake of selenite,selenomethionine and selenate by brush border membrane vesicles isolated from rat small intestine

The uptake of selenite, selenate and selenomethionine (SeMet) was performed with brush border membrane vesicles (BBMV) prepared from rats fed selenium-deficient and supplemented diets. At equilibrium (60 min), the uptake of ⁷⁵Se from [⁷⁵Se]selenite ranged from 16.5 to 18.9 nmol mg^-1 protein. There was a curvilinear relationship in the uptake of selenite over a concentration range of 10–1000 m. About 2 nmol mg^-1 protein was obtained with selenomethionine (SeMet) which occurred between 90 and 180 s. In contrast to selenite, there was a linear relationship in the initial uptake of SeMet over a concentration range of 10–1000 m. The uptake of selenate was approximately 50-fold lower than selenite, reaching 350 pmol mg^-1 protein. Dietary selenium level had no effect on the rate of ⁷⁵Se accumulation by BBMV. Dramatic differences are found in the uptake and binding of selenium by BBMV incubated with different selenocompounds.     

Protein metabolism in the small intestine of the ethanol-fed rat

The effects of chronic ethanol feeding on the small intestine were investigated in young rats. Rats were fed a nutritionally-adequate liquid diet, containing 36 per cent of total energy as ethanol (treated, n = 7), or isovolumetric amounts of the same diet in which ethanol was substituted by isocaloric glucose (controls, n = 7). After six weeks the wet weight and total tissue contents of protein, RNA and DNA were significantly reduced by 21 per cent, 23 per cent, 16 per cent and 28 per cent respectively, (p less than 0.014). Rates of protein synthesis were measured with L[4(3H)]phenylalanine and fractional rates (defined as the percentage of constituent tissue protein synthesised each hour, i.e. ks, % h-1) were calculated from the specific radioactivity of free phenylalanine in both tissue homogenates and plasma. Ethanol-feeding reduced ks by approx 10 per cent (p less than 0.181). The amount of protein synthesized unit-1 RNA was also reduced by approx 15 per cent (p less than 0.059) but the amount of protein synthesis unit-1 DNA was unaffected by ethanol-feeding (p less than 1.000). In contrast, the absolute rates of protein synthesis were reduced by approximately 30 per cent (p less than 0.022). It was concluded that, as the small intestine contributes to approx. 20-25 per cent of whole body synthesis these results may have an important effect on whole body nitrogen homeostasis and may have implications for the gastrointestinal effects of ethanol seen during chronic alcoholic abuse.     

Inhibitory effect of aluminium on calcium absorption in small intestine of rats with different thyroid hormone status

To analyse the influence of thyroid status on the effect of aluminium (Al) upon intestinal calcium (Ca) absorption, adult male Wistar rats with experimentally altered thyroid hormones circulating levels, were orally treated (o.g.) with 0 (control), or 50 mg elemental Al (as chloride)/kg body weight (b.w.) per day, for a 14 d period. Hyper- and hypo-thyroid conditions were respectively achieved by means of administration of either sodium levothyroxine (50 μg/kg b.w. per day, o.g.) or methimazole, a thyroxine synthesis inhibitor (1 mg/kg b.w. per day, o.g.). In duodenum–jejunum segments, in vitro mucosa-to-serosa ⁴⁵Ca flux (JCa_ms) and kinetics of ⁴⁵Ca uptake in isolated enterocytes, were determined. In serum, concentrations of thyroxine (T4) and triiodothyronine (T3) were measured by chemiluminescent enzyme immunoassay. Unlike non-Al-treated rats, JCa_ms of Al-exposed rats decreased as serum levels of T4 and T3 increased, showing a significant inverse correlation in both cases (T4: r² = 0.414, P = 0.024; T3: r² = 0.443, P = 0.018). Enterocytes isolated from rats treated with Al plus thyroxine showed a reduction of both maximum Ca uptake (4.86 ± 0.44 vs. 6.85 ± 1.04 nmol Ca/mg protein, P < 0.05) and K_m (0.84 ± 0.18 vs. 1.05 ± 0.36 mM, P < 0.05) when compared to control. The observed variability in the Al effect on Ca transport with thyroid status of rats could be reflecting a negative interaction of Al with thyroid hormone action mechanisms on intestinal Ca absorption, which would take place mainly at Ca entry into enterocyte from lumen.     

Endocrine cells in the human fetal small intestine

Summary In this report we describe the time of appearance and ultrastructural features of enteroendocrine cells (EECs) in the human fetal small intestine (SB) between 9 and 22 weeks gestation. Thirteen distinctive EECs were identified in fetal SB. Two of these, not found in normal adult SB, appeared within the stratified epithelium of the proximal SB at 9–10 weeks. They were arbitrarily termed primitive and precursor cells. As in all fetal EECs, the pale cytoplasm of the primitive cell contains a distinctive population of secretory granules (SGs). Primitive cell SGs average 200–330 nm; some have dense cores with lucent halos while others are filled with a homogeneous dense or flocculent material. The SGs of the precursor cells are larger, averaging up to 1 m in diameter and their contents vary in electron density. A third group of cells not described in normal adult SB was arbitrarily termed transitional cells. These have two populations of SGs; one resembles the SGs of the precursor cells, and the other resembles the SGs of some of the specific adult type EECs. Transitional EC, S, I and G cells are seen. In addition, mature appearing EC, S, G, I, L, D, and D₁ cells were identified by 12 weeks of gestation. The primitive, precursor, and transitional cells may represent sequential developmental precursors of adult type EECs.Supported by Research Grant AM-17537 from the National Institutes of Health, Besthesda, MarylandThe authors would like to thank Ms. Linda Barstein for her excellent technical assistance     

Immunofluorescent localization of transglutaminase in rat small intestine

The distribution of intestinal transglutaminase was investigated by immunofluorescence microscopy using rabbit anti-guinea pig transglutaminase immunoglobulin. Transglutaminase-related antigen was demonstrated principally in the cytoplasm of villous core interstitial cells with some activity in the brush border region of the villous epithelial cells. Implications for the pathogenesis of coeliac disease are discussed.     

Walker 256 tumour growth causes marked changes of glutamine metabolism in rat small intestine

The effect of Walker 256 tumour growth on the metabolism of glucose and glutamine in the small intestine of rats was examined. Walker 256 tumour has been extensively used as an experimental model to induce cancer cachexia in rats. Walker 256 tumour growth decreased body weight and small intestine weight and length. The activities of glucose-6-phosphate dehydrogenase and phosphate-dependent glutaminase were reduced in the proximal, median and distal portions of the intestine. Glutamine oxidation was reduced in the proximal portion only. The decrease in glutaminase activity was not due to a low synthesis of the protein as indicated by Western blotting analysis. Hexokinase and citrate synthase activities were not changed by the tumour. These findings led us to postulate that tumour growth impairs glutamine metabolism of small intestine but the mechanism involved remains to be elucidated.     

一氧化碳减轻脂多糖诱导的大鼠小肠损伤与p38 MAPK磷酸化水平的关系

目的：观察低浓度一氧化碳（CO）吸入和腹腔给予对脂多糖（LPS）诱导大鼠小肠损伤的作用及作用过程中丝裂原活化蛋白激酶p38（p38 MAPK）磷酸化水平的变化。方法：6组SD大鼠静脉注入5mg／kg体质量IPS或等容量生理盐水;1h后,对照及LPS注入组吸入室内空气,CO吸入及LPS注入＋CO吸入组吸入体积分数为2．5×10^-4CO．CO腹腔及LPS注入＋CO腹腔组腹腔通入体积分数为2．5×10^-4CO。观察1、3、6h后放血处死,取回盲部上小肠,酶联免疫吸附法测定血小板活化因子（PAV）及细胞间黏附分子-1（ICAM-1）水平;光镜观察组织形态学变化;蛋白印迹法测定p38 MAPK磷酸化水平。结果：LPS注入组PAF、ICAM-1及p38 MAPK磷酸化水平显著高于相应时间点的对照、CO吸入及CO腹腔组（P均〈0．01）;组内各时间点比较,差异无统计学意义。与相应时间点的LPS注入组比较,LPS注入＋CO吸入及LPS注入＋CP腹腔组的PAF和ICAM-1明显降低（P均〈0．05）,但p38 MAPK磷酸化水平进一步增高（P均〈0．05）;此两组间及两组内各时间点比较,差异无统计学意义。结论：低浓度CO吸入和腹腔给予以非时间依赖方式下调LPS诱导的大鼠小肠PAF、ICAM-1表达而起相似的保护作用;p38 MAPK信号转导通路可能参与了这一过程。     

Effect of protein deficiency on macroelement and trace element levels of weanling rats' small intestine and liver tissues

Protein energy malnutrition has become a major health issue in developing countries. In the present study, the effect of protein deficiency on the small intestine and liver tissue content of macroelements and trace elements was investigated in weanling rats. Forty-five male weanling Wistar albino rats were divided into three groups. The control group (C) was fed a standard diet containing 25% casein, whereas the two experimental groups E1 and E2 consumed 12% and 3% casein, respectively, over a period of 45 d. The tissue samples were analyzed for zinc, copper, iron, manganese, calcium, and magnesium by atomic absorption spectroscopy. The protein-deficient groups showed increased levels of iron in both tissues and decreased manganese in small intestine tissue from the E1 group. No other differences were found for the other elements. These results suggest that protein deficiency might cause iron accumulation in the liver and intestine and decreases of manganese in the small intestine.     

The response of the small intestine of the protein-deficient rat to infection with Nippostrongylus brasiliensis

The intestinal response of the protein-deficient Wistar rat was examined after primary infection with 1500 larvae of Nippostrongylus brasiliensis. Protein-deficient animals failed to expel N. brasiliensis after 15 days at a time when nutritionally normal animals had expelled more than 99% of the worm burden. Morphology of the small intestine of protein-deficient animals before infection showed small villi and crypt hypoplasia, followed after infection by sustained crypt hyperplasia and increased mitotic index of crypts. Protein deficiency was associated with fewer mucosal mast cells, goblet cells and intraepithelial lymphocytes. There was an impaired response of mucosal mast cells and goblet cells to infection. This could explain the deficiency of worm expulsion in these protein-deficient animals.     

Expression of differentiated functions in the developing porcine small intestine

Heterologous cDNA clones were used as hybridization probes to define the temporal expression of intestinal functions during fetal and postnatal development in the pig. Northern hybridization analysis revealed the presence of the mRNAs for the cellular retinol binding protein CRBP II, for the digestive enzyme aminopeptidase N, and for the microvillar proteins villin and ezrin in the small intestine of both weaned and 40-day fetal pigs. The presence of these mRNAs suggests that at the end of the first third of gestation the pig fetal intestine is already exhibiting some characteristics of a differentiated epithelium. The mRNAs for the two fatty acid-binding proteins I-FABP and L-FAPB, both involved in the metabolism of long chain fatty acids, were detected only in the intestinal mRNA extracted from weaned animals, while that for the cellular retinol-binding protein CRBP I was expressed only in the fetal tissue. The temporal limits of expression of intestinal genes in the pig epithelium seem therefore more easily defined than in other experimental animals with shorter times of fetal development. To isolate pig genes expressed at different developmental stages during intestinal epithelial cell differentiation, a cDNA library was constructed from poly(A) + RNA extracted from mature pig intestine. This library was employed in the isolation of clones encoding CRBP II and L-FABP. The nucleotide sequence of the two pig cDNA clones was determined, and the sequences of the deduced proteins compared with their homologues from other species. The results of this analysis showed that the two pig clones share a high level of homology with human and rat homologues both at the DNA and at the protein level.     

Guanine nucleotides regulate [3H]substance P binding in rat small intestine

The binding of [3H]substance P (SP) to membranes of the rat small intestine demonstrates specific binding to receptors having more than one affinity for SP. The values of the binding parameters for the high-affinity site obtained from a non-linear regression analysis are as follows: KD = 0.25 nM, Bmax = 149.5 fmol/mg protein. Inhibition curves of 3H-SP binding using various unlabeled tachykinins show that the high-affinity receptor is of the P-subtype, having the highest affinity for SP and lower affinities for eledoisin and kassinin. Guanine nucleotides and sodium independently reduce the binding of 3H-SP to the high-affinity receptor in a dose-related manner; GTP and GDP are more potent than GMP. The reduction of specific SP binding by GTP can be ascribed primarily to an increase in the off-rate. The effects of guanine nucleotides on 3H-SP binding to membranes of rat small intestine suggest that the high-affinity receptor is linked to an effector by a GTP-binding regulatory protein.     

Prednisolone enhances aminopeptidase turnover in adult rat small intestine

In adult male rats, fed prednisolone (0.75 mg/kg/day) for 7 days, brush border aminopeptidase activity was increased (P < 0.001) by 106% compared to pair-fed controls. [¹⁴C]Tyrosine was injected intraperitoneally 16 h and [³H]tyrosine 6 h before death. The ³H/¹⁴C ratio was 1.79 ± 0.21 (S.D.) in purified microvillus membranes from treated rats compared to 1.30 ± 0.16 (P < 0.01) in controls. Polyacrylamide gel electrophoresis of brush border membranes under denaturing conditions showed that the increased double-isotope ratio in membranes from treated rats was mainly in the high molecular weight protein subunits (> 80 kDa) Detergent-solubilized aminopeptidase was purified after in vivo labeling by protein A-Sepharose-antiaminopeptidase affinity chromatography. The ³H/¹⁴C ratio in aminopeptidase was 2.42 ± 0.15 (P < 0.05) in treated rats compared to 1.63 ± 0.13 in controls. Over the experimental period steady-state isotope reutilization and protein labeling was demonstrated and there was no isotope metabolism. Total microvillus membrane lipid content was unaffected by prednisolone. We conclude that prednisolone increases brush border aminopeptidase activity by increasing enzyme turnover. Other high molecular weight brush border proteins were similarly affected.     

Intestinal absorption of hexoses in rats infected with Nippostrongylus brasiliensis

The net absorption and accumulation of d-galactose and d-glucose by the small intestine of rats infected with N. brasiliensis were studied in vivo and in vitro. There was no change from control levels in the rate of galactose transfer in vivo by the entire intestine 10 days after infection but fluid transfer was significantly lower at this time. Mucosal galactose transfer in vitro by the entire intestine or by each one-third of the intestine did not change significantly during infection but 10 days after infection mucosal glucose transfer was significantly lower in the infected proximal one-third of the intestine and significantly greater in the distal one-third than in the comparable segments in controls; mucosal glucose transfer by the entire intestine was not affected by infection. Serosal transfer of both hexoses by the proximal two-thirds of the intestine and by the entire intestine was significantly reduced 10 days after infection. Between 10 and 18 days after infection the rate of serosal galactose transfer in vitro was significantly lower than control levels. The difference in response of mucosal and serosal hexose transfer rates to infection appears to be due, in part, to an increase in intestinal glucose metabolism or increased tissue retention of galactose during infection. Mucosal fluid transfer in vitro by the entire intestine was not significantly different from control levels at 10 days of infection when either hexose was used, although there was a significant reduction in the jejunal segment when glucose was used. Mucosal fluid transfer by the entire intestine in the presence of galactose was significantly greater during the rejection phase of the parasite population than in controls.     

Effects of ceftriaxone‐induced intestinal dysbacteriosis on dendritic cells of small intestine in mice

Intestinal microflora plays a pivotal role in the development of the innate immune system and is essential in shaping adaptive immunity. Dysbacteriosis of intestinal microflora induces altered immune responses and results in disease susceptibility. Dendritic cells (DCs), the professional antigen‐presenting cells, have gained increasing attention because they connect innate and adaptive immunity. They generate both immunity in response to stimulation by pathogenic bacteria and immune tolerance in the presence of commensal bacteria. However, few studies have examined the effects of intestinal dysbacteriosis on DCs. In this study, changes of DCs in the small intestine of mice under the condition of dysbacteriosis induced by ceftriaxone sodium were investigated. It was found that intragastric administration of ceftriaxone sodium caused severe dysteriosis in mice. Compared with controls, numbers of DCs in mice with dysbacteriosis increased significantly (P = 0.0001). However, the maturity and antigen‐presenting ability of DCs were greatly reduced. In addition, there was a significant difference in secretion of IL‐10 and IL‐12 between DCs from mice with dysbacteriosis and controls. To conclude, ceftriaxone‐induced intestinal dysbacteriosis strongly affected the numbers and functions of DCs. The present data suggest that intestinal microflora plays an important role in inducing and maintaining the functions of DCs and thus is essential for the connection between innate and adaptive immune responses.     

Investigation of the protective effects of crocin on acrylamide induced small and large intestine damage in rats

We investigated repair of acrylamide (AA) induced damage in intestines by administration of crocin. We used 40 male Wistar rats in four groups of 10 animals: control, AA, crocin, and AA + crocin groups. We investigated biochemical and histological changes to small and large intestine. AA ingestion decreased glutathione (GSH) levels and total antioxidant status (TAS) in the intestine compared to the control group, while superoxide dismutase (SOD) and catalase (CAT) activities, and total oxidant status (TOS) and malondialdehyde (MDA) levels were increased. Villi were shortened and villus degeneration was observed in ileum of the AA group. Degeneration of surface epithelium and Liberkühn crypts were observed in colon sections. GSH and TAS levels increased after administration of AA together with crocin, while SOD and CAT levels and TOS and MDA levels decreased; significant recovery of histological damage also was observed. We found that crocin exhibits protective effects on AA induced small and large intestine damage by inhibiting oxidative stress.