L-Glutamate Supplementation Improves Small Intestinal Architecture and Enhances the Expressions of Jejunal Mucosa Amino Acid Receptors and Transporters in Weaning Piglets

L-Glutamate is a major oxidative fuel for the small intestine. However, few studies have demonstrated the effect of L-glutamate on the intestinal architecture and signaling of amino acids in the small intestine. The aim of this study was to investigate the effects of dietary L-glutamate supplementation on the intestinal architecture and expressions of jejunal mucosa amino acid receptors and transporters in weaning piglets. A total of 120 weaning piglets aged 35±1 days with an average body weight at 8.91±0.45 kg were randomly allocated to two treatments with six replicates of ten piglets each, fed with diets containing 1.21% alanine, or 2% L-glutamate. L-Glutamate supplementation increased the activity of glutamate oxaloacetate transaminase (GOT) in the jejunal mucosa. Also, the mRNA expression level of jejunal mucosa glutamine synthetase (GS) was increased by L-glutamate supplementation. The height of villi in duodenal and jejunal segments, and the relative mRNA expression of occludin and zonula occludens protein-1 (ZO-1) in jejunal mucosa were increased by dietary L-glutamate supplementation. L-Glutamate supplementation increased plasma concentrations of glutamate, arginine, histidine, isoleucine, leucine, methionine, phenylalanine and threonine. L-Glutamate supplementation also increased the relative mRNA expression of the jejunal mucosa Ca²⁺-sensing receptor (CaR), metabotropic glutamate receptor 1 (mGluR1) and metabotropic glutamate receptor 4 (mGluR4), and neutral amino acid transporter B⁰-like (SLC1A5) in the jejunal mucosa. These findings suggest that dietary addition of 2% L-glutamate improves the intestinal integrity and influences the expression of amino acid receptors and transporters in the jejunum of weaning, which is beneficial for the improvement of jejunal nutrients for digestion and absorption.     

Protective effects of N-acetylcysteine on intestinal functions of piglets challenged with lipopolysaccharide

The neonatal small intestine is susceptible to damage by endotoxin, but effective methods for prevention and treatment are lacking. N-acetylcysteine (NAC) is a widely used precursor of L: -cysteine for animal cells and plays an important role in protecting cells against oxidative stress. This study was conducted with the lipopolysaccharide (LPS)-challenged piglet model to determine the effects of NAC on intestinal function. Eighteen piglets were randomly allocated into control, LPS and LPS?+?NAC groups. The control and LPS groups were fed a corn- and soybean meal-based diet, and the LPS?+?NAC group was fed the basal diet +500?mg/kg NAC. On days 10, 13 and 20 of the trial, the LPS and LPS?+?NAC groups received intraperitoneal administration of LPS (100?μg/kg BW), whereas the control piglets received saline. On day 20 of the trial, D-: xylose (0.1?g/kg BW) was orally administrated to all piglets 2?h after LPS or saline injection, and blood samples were collected 1?h thereafter. One hour blood xylose test was used to measure intestinal absorption capacity and mucosal integrity, and diamine oxidase (DAO) was used as a marker of intestinal injury. On day 21 of the trial, pigs were killed to obtain the intestinal mucosa. Compared to the control, LPS challenge reduced (P?相似文献   

β-Glucan extracts inhibit the in vitro intestinal uptake of long-chain fatty acids and cholesterol and down-regulate genes involved in lipogenesis and lipid transport in rats

BackgroundDietary fiber reduces the intestinal absorption of nutrients and the blood concentrations of cholesterol and triglycerides.AimWe wished to test the hypothesis that high-viscosity (HV) and low-viscosity preparations of barley and oat β-glucan modify the expression of selected genes of lipid-binding proteins in the intestinal mucosa and reduce the intestinal in vitro uptake of lipids.MethodsFive different β-glucan extracts were separately added to test solutions at concentrations of 0.1–0.5% (wt/wt), and the in vitro intestinal uptake of lipids into the intestine of rats was assessed. An intestinal cell line was used to determine the effect of β-glucan extracts on the expression of intestinal genes involved in lipid metabolism and fatty acid transport.ResultsAll extracts reduced the uptake of 18:2 when the effective resistance of the unstirred water layer was high. When the unstirred layer resistance was low, the HV oat β-glucan extract reduced jejunal 18:2 uptake, while most extracts reduced ileal 18:2 uptake. Ileal 18:0 uptake was reduced by the HV barley extract, while both jejunal and ileal cholesterol uptakes were reduced by the medium-purity HV barley extract. The inhibitory effect of HV barley β-glucan on 18:0 and 18:2 uptake was more pronounced at higher fatty acid concentrations. The expression of genes involved in fatty acid synthesis and cholesterol metabolism was down-regulated with the HV β-glucan extracts. β-Glucan extracts also reduced intestinal fatty-acid-binding protein and fatty acid transport protein 4 mRNA.ConclusionsThe reduced intestinal fatty acid uptake observed with β-glucan is associated with inhibition of genes regulating intestinal uptake and synthesis of lipids. The inhibitory effect of β-glucan on intestinal lipid uptake raises the possibility of their selective use to reduce their intestinal absorption.     

Diurnal rhythm in mRNA expression of genes encoding amino acid transporter and circadian gene cry in intestinal mucosa of piglets

Long chain PUFA contents in plasma and liver both exhibited diurnal rhythms in pigs. However, whether mRNA expression of amino acid transporter and circadian gene Cry in intestinal mucosa is also rhythmic is yet to be known. The purpose of this study aims to investigate the diurnal rhythm in mRNA expression of genes encoding amino acid transporter and whether their rhythm was related to the expression of circadian gene Cry in intestinal mucosa of piglets. Thirty-six piglets (Duroc?×?Landrace?×?Large Yorkshire) at the age of 35 days were selected and fed for three weeks, and then samples were collected at 3:00 am (Clo3), 7:00 am (Clo7), 11:00 am (Clo11), 3:00 pm (Clo15), 7:00 pm (Clo19), and 11:00 pm (Clo23) at the age of 56 days. At each time point, small intestinal mucosa samples were collected from duodenum, jejunum, and ileum for detection of mRNA expression of the amino acid transporters and circadian gene Cry. The results showed that mRNA expression of most amino acid transporters in intestinal mucosa was higher at night and lower during the daytime. Expression of SLC1A2, SLC6A20, SLC7A1, and SLC6A14 in duodenal mucosa reached the peak at Clo3 and Clo7; the diurnal rhythm of expression of SLC1A2, SLC6A20, and SLC7A1 was similar to Cry1, while the diurnal rhythm of expression of SLC6A14 had a similar trend to Cry2. Expression of SLC16A10, SLC1A2, and SLC7A1 in jejunal mucosa reached the peak at Clo7, while SLC6A14 reached the peak at Clo3; the diurnal rhythm of expression of SLC1A2 showed a similarity with Cry1, while the diurnal rhythm of expression of SLC16A10, SLC7A1, and SLC6A14 was similar to Cry2. Expression of SLC6A14, SLC6A20, and SLC7A1 in ileal mucosa reached the peak at Clo3; the diurnal rhythm of expression of SLC6A20 has a similarity with Cry1, while the diurnal rhythm of expression of SLC7A1 and SLC6A14 was similar to Cry2. The results suggested that the mRNA expression of most genes encoding amino acid transporters exhibited diurnal rhythms in the intestinal mucosa of piglets, and SLC7A1, SLC6A14, and SLC1A2 have a similar rhythm with circadian clock genes Cry1 and 2, and they reached the peak at Clo3 and Clo7.     

Dietary supplementation of aspartate enhances intestinal integrity and energy status in weanling piglets after lipopolysaccharide challenge

The intestine has a high requirement for ATP to support its integrity, function and health, and thus, energy deficits in the intestinal mucosa may play a critical role in intestinal injury. Aspartate (Asp) is one of the major sources of ATP in mammalian enterocytes via mitochondrial oxidation. We hypothesized that dietary supplementation of Asp could attenuate lipopolysaccharide (LPS)-induced intestinal damage via modulation of intestinal energy status. Twenty-four weanling piglets were allotted to one of four treatments: (1) nonchallenged control, (2) LPS-challenged control, (3) LPS+0.5% Asp treatment, and (4) LPS+1.0% Asp treatment. On day 19, pigs were injected with saline or LPS. At 24 h postinjection, pigs were killed and intestinal samples were obtained. Asp attenuated LPS-induced intestinal damage indicated by greater villus height and villus height/crypt depth ratio as well as higher RNA/DNA and protein/DNA ratios. Asp improved intestinal function indicated by increased intestinal mucosal disaccharidase activities. Asp also improved intestinal energy status indicated by increased ATP, ADP and total adenine nucleotide contents, adenylate energy charge and decreased AMP/ATP ratio. In addition, Asp increased the activities of tricarboxylic acid cycle key enzymes including citrate synthase, isocitrate dehydrogenase and alpha-oxoglutarate dehydrogenase complex. Moreover, Asp down-regulated mRNA expression of intestinal AMP-activated protein kinase α1 (AMPKα1), AMPKα2, silent information regulator 1 (SIRT1) and peroxisome proliferator–activated receptor gamma coactivator-1α (PGC1α) and decreased intestinal AMPKα phosphorylation. These results indicate that Asp may alleviate LPS-induced intestinal damage and improve intestinal energy status.     

Transcellular mechanisms of amino acid uptake by distal rat ileum in situ

A 10 cm distal ileal intestinal perfusion technique was employed in Sprague-Dawley rats in situ. The perfused segment was removed, weighed, its surface area measured, homogenized, digested in HNO3 and assayed for L(1-14C)alanine and L-phenyl (1-14C)alanine. Steady state for L-alanine and L-phenylalanine absorption by the intact intestinal segment was observed at 10 and 15 min respectively. Exposure of the intestinal mucosa to 1 mM ouabain showed no effect on amino acid absorption. Preloading the intestinal epithelium with ouabain resulted in approximately 66% and 48% reduction in L-alanine and L-phenylalanine absorption respectively. Removal of Na from the buffer with and without exposure of the mucosa to 1 mM ouabain decreased absorption of L-alanine and L-phenylalanine by approximately 77% and 52% respectively. Removal of Na from the buffer and preloading the intestinal epithelium with ouabain resulted in approximately 85% and 81% reduction in L-alanine and L-phenylalanine absorption respectively. A 5, 10 and 25 fold increase in luminal L-alanine and L-phenylalanine concentration in Na-free choline Krebs Ringer after preloading with ouabain resulted in increase of amino acid absorption of approximately the same order of magnitude. Both an amino acid-carrier mediated transport process and a ouabain resistant Na-dependent-amino acid pump exist at the mucosal side. Both an ouabain sensitive Na-dependent-amino acid pump and an ouabain resistant Na-independent amino acid pump exist at the serosal side. Approximately 15-20% of absorbed amino acids are passively translocated.     

A moderate threonine deficiency affects gene expression profile,paracellular permeability and glucose absorption capacity in the ileum of piglets

High dietary threonine extraction by the digestive tract suggests that threonine contributes to maintain gut physiology. In the present study, we evaluated the impact of a low (6.5 g of threonine/kg diet; LT group) or a control well-balanced threonine diet (9.3 g of threonine/kg diet; C group) given to piglets for 2 weeks on ileal permeability and Na+-dependant glucose absorption capacity in Ussing chambers. The paracellular permeability was significantly increased in the ileum of LT compared to C piglets (P=.017). The Na+-dependent glucose absorption capacity showed a nonsignificant increase in the LT piglets. In addition, we analysed ileal gene expression profiles in the LT and C groups using porcine multitissue cDNA microarrays. Compared to the C piglets, the expression of 324 genes was significantly modified in the ileum of the LT piglets: 214 genes were overexpressed (145 annotated) and 110 were down-expressed (79 annotated). Among them, some are involved in immune and defense responses, energy metabolism and protein synthesis. Furthermore, microarray analysis highlights changes in the expression of the gene encoding for the sodium/glucose cotransporter (SGLT1) and of genes involved in the regulation of paracellular permeability (ZO-1, cingulin and myosin light chain kinase). In conclusion, our results indicate that a moderate threonine deficiency affects intestinal functionality.     

The growth performance,intestinal digestive and absorptive capabilities in piglets with different lengths of small intestines

The small intestine is an important digestive organ and plays a vital role in the life of a pig. We tested the hypothesis that the length of the small intestine is related to growth performance and intestinal functions of piglets. A total of 60 piglets (Duroc × Landrace × Yorkshire), weaned at day 21, were fed an identical diet during a 28-day trial. At the end of the study, all piglets were sacrificed, dissected and grouped according to small intestine lengths (SILs), either short small intestine (SSI), middle small intestine (MSI) or long small intestine (LSI), respectively. Positive relationships between SIL and BW, average daily gain (ADG), average daily feed intake (ADFI) and gain-to-feed ratios (G : F) were observed. Final BW, ADG, ADFI and G : F significantly increased (P < 0.05) in MSI and LSI piglets compared with SSI piglets. Short small intestine and MSI had greater jejunal mucosa sucrase and alkaline phosphatase activities (P < 0.05) than LSI piglets. The mRNA level of solute carrier family 2 member 2 (Slc2a2) in the jejunal mucosa of SSI piglets was the greatest. The MSI piglets had a greater (P < 0.05) ileal villus height than other piglets and greater (P < 0.05) villus height-to-crypt depth ratios than LSI piglets. However, the LSI piglets had a greater (P < 0.05) ileal crypt depth than SSI piglets. No significant differences in duodenal, jejunal, caecal and colonic morphologies were detected among the groups. Moreover, luminal acetate, propionate, butyrate and total short-chain fatty acid contents were greater (P < 0.05) in SSI and MSI piglets than those in LSI piglets. In addition, there was greater serum glucose concentration in MSI piglets than other piglets. Serum albumin concentration in SSI piglets was the lowest. In conclusion, these results indicate that SIL was significantly positively associated with growth performance, and in terms of intestinal morphology and mucosal digestive enzyme activity, the piglets with a medium length of small intestine have better digestion and absorption properties.     

Amino acid metabolism and the energetics of growth

The nonessential amino acids are involved in a large number of functions that are not directly associated with protein synthesis. Recent studies using a combination of transorgan balance and stable isotopic tracers have demonstrated that a substantial portion of the extra‐splanchnic flux of glutamate, glutamine, glycine and cysteine derives from tissue synthesis. A key amino acid in this respect is glutamic acid. Little glutamic acid of dietary origin escapes metabolism in the small intestinal mucosa. Furthermore, because glutamic acid is the only amino acid that can be synthesized by mammals by reductive amination of a ketoacid, it is the ultimate nitrogen donor for the synthesis of other nonessential amino acids. Because the synthesis of glutamic acid and its product glutamine involve the expenditure of adenosine triphosphate (ATP), it seems possible that nonessential amino acid synthesis might have a significant bearing on the energetics of protein synthesis and, hence, of protein deposition. This paper discusses the topic of the energy cost of protein deposition, considers the metabolic physiology of amino acid oxidation and nonessential amino acid synthesis, and attempts to combine the information to speculate on the overall impact of amino acid metabolism on the energy exchanges of animals.     

Chlorogenic acid improves intestinal barrier functions by suppressing mucosa inflammation and improving antioxidant capacity in weaned pigs

Intestinal barrier plays key roles in maintaining intestinal homeostasis. Inflammation and oxidative damage can severely destroy the intestinal integrity of mammals. Chlorogenic acid (CGA) is a natural polyphenol present in human diet and plants, possessing potent antioxidant and anti-inflammatory activities. This study was conducted to investigate the protective effects of CGA and its molecular mechanisms on intestinal barrier function in a porcine model. Twenty-four weaned pigs were allotted to two groups and fed with a basal diet or a basal diet containing 1000 mg/kg CGA. The results showed that CGA decreased serum D-lactate and diamine oxidase levels, and enhanced the expression and localization of claudin-1 protein in apical intercellular region of small intestinal epithelium. Interestingly, CGA significantly decreased the mucosa histamine and tryptase contents, as well as the tryptase-positive mast cell counts. Moreover, the expression levels of critical inflammation molecules (interleukin-1β, interleukin-6, tumor necrosis factor-α, and nuclear factor-κB) were down-regulated by CGA in jejunal and ileal mucosa. However, the expression levels of inflammation repressors (suppressor of cytokine signaling 1 and toll-interacting protein) were up-regulated by CGA. Importantly, CGA decreased the malondialdehyde content but elevated glutathione peroxidase and catalase content in duodenal and jejunal mucosa. The expression levels of critical molecules in antioxidant signaling (nuclear factor erythroid-derived 2-related factor 2 and heme oxygenase-1) were elevated by CGA in duodenal and jejunal mucosa. These results suggested that CGA could ameliorate intestinal barrier disruption in weaned pigs, which might be mediated by suppressing the TLR4/NF-κB signaling pathway and activating the Nrf2/HO-1 signaling pathway.     

Characterization and Regulation of the Amino Acid Transporter SNAT2 in the Small Intestine of Piglets

The sodium-dependent neutral amino acid transporter 2 (SNAT2), which has dual transport/receptor functions, is well documented in eukaryotes and some mammalian systems, but has not yet been verified in piglets. The objective of this study was to investigate the characteristics and regulation of SNAT2 in the small intestine of piglets. The 1,521-bp porcine full cDNA sequence of SNAT2 (KC769999) from the small intestine of piglets was cloned. The open reading frame of cDNA encodes 506 deduced amino acid residues with a calculated molecular mass of 56.08 kDa and an isoelectric point (pI) of 7.16. Sequence alignment and phylogenetic analysis revealed that SNAT2 is highly evolutionarily conserved in mammals. SNAT2 mRNA can be detected in the duodenum, jejunum and ileum by real-time quantitative PCR. During the suckling period from days 1 to 21, the duodenum had the highest abundance of SNAT2 mRNA among the three segments of the small intestine. There was a significant decrease in the expression of SNAT2 mRNA in the duodenal and jejunal mucosa and in the expression of SNAT2 protein in the jejunal and ileal mucosa on day 1 after weaning (P < 0.05). Studies with enterocytes in vitro showed that amino acid starvation and supplementation with glutamate, arginine or leucine enhanced, while supplementation with glutamine reduced, SNAT2 mRNA expression (P < 0.05). These results regarding the characteristics and regulation of SNAT2 should help to provide some information to further clarify its roles in the absorption of amino acids and signal transduction in the porcine small intestine.     

Protective effects of nocardia delipidated cell mitogen on the mucosa of the small intestine after irradiation of germ-free piglets.

The radioprotective effect of the bacterial immunomodulator Nocardia delipidated cell mitogen (NDCM) on intestinal mucosa and disaccharidase activities was studied in irradiated germ-free piglets. Three-week-old germ-free (GF) piglets were intragastrically pretreated with 1 mg NDCM per 1 kg body weight. The piglets were whole-body irradiated with 2.5 Gray five days after the NDCM pretreatment and sacrificed eight days after irradiation. In the non-irradiated group of GF piglets, NDCM application stimulated lactase activity and markedly increased sucrase activity. This stimulatory effect of NDCM disappeared after irradiation and the piglets exhibited a normal activity of lactase in the jejunal brush-border membrane vesicles, while the sucrase activity decreased to the level found in irradiated controls. NDCM-pretreated intestinal mucosa contained some infrequent lymphocytes which disappeared from the control irradiated tissue. It also exhibited less injury of the epithelium and stroma cells.     

Effects of Weaning on Intestinal Upper Villus Epithelial Cells of Piglets

The intestinal upper villus epithelial cells represent the differentiated epithelial cells and play key role in digesting and absorbing lumenal nutrients. Weaning stress commonly results in a decrease in villus height and intestinal dysfunction in piglets. However, no study have been conducted to test the effects of weaning on the physiology and functions of upper villus epithelial cells. A total of 40 piglets from 8 litters were weaned at 14 days of age and one piglet from each litter was killed at 0 d (w0d), 1 d (w1d), 3 d (w3d), 5 d (w5d), and 7 d (w7d) after weaning, respectively. The upper villus epithelial cells in mid-jejunum were isolated using the distended intestinal sac method. The expression of proteins in upper villus epithelial cells was analyzed using the isobaric tags for relative and absolute quantification or Western blotting. The expression of proteins involved in energy metabolism, Golgi vesicle transport, protein amino acid glycosylation, secretion by cell, transmembrane transport, ion transport, nucleotide catabolic process, translational initiation, and epithelial cell differentiation and apoptosis, was mainly reduced during the post-weaning period, and these processes may be regulated by mTOR signaling pathway. These results indicated that weaning inhibited various cellular processes in jejunal upper villus epithelial cells, and provided potential new directions for exploring the effects of weaning on the functions of intestine and improving intestinal functions in weaning piglets.     

Effect of cholera toxin on glutamine metabolism and transport in rabbit ileum

The aim of the present study was to evaluate the effect of cholera toxin on energy balance from intestinal glutamine metabolism and oxidation, glutamine-dependent sodium absorption, and cholera toxin-dependent ion flux. Cholera toxin-stimulated sodium and L-glutamine ileal transport and metabolism were studied in Ussing chambers. Glutamine (10 mM) transport and metabolism were simultaneously studied using (14)C flux and HPLC. In the same tissues, the flux of each amino acid was studied by HPLC, and glutamine metabolism and oxidation were studied by the determination of amino acid specific activity and (14)CO(2) production. In control tissues, glutamine stimulated sodium absorption and was mainly oxidized. The transepithelial flux of intact glutamine represented 45% of glutamine flux across the luminal membrane. The other metabolites were glutamate and, to a lesser degree, citrulline, ornithine, and proline. Cholera toxin did not alter glutamine-stimulated sodium absorption, glutamine oxidation, transport, and metabolism. In conclusion, the present results indicate that cholera toxin does not alter glutamine intestinal function and metabolism. In addition, approximately 95% of the energy provided by glutamine oxidation remains available to the enterocyte.     

Amino acids modulates the intestinal proteome associated with immune and stress response in weaning pig

The objective of this study was to investigate the effects of free amino acids supplementation to protein restricted diet on the intestinal morphology and proteome composition in weaning pigs. Weanling piglets were randomly fed one of the three diets including a corn-soybean based control diet and two lower protein diets with or without free amino acids supplementation for 2 weeks. The jejunum samples of piglets were collected for morphology and proteome analysis. Compared with the control diet, the protein restricted diet had a significant lower average daily gain and higher feed conversion rate. Free amino acids supplementation to the protein restricted diet significantly improved average daily gain and higher feed conversion rate, compared with the protein restricted diet. The villous height in pigs fed the protein restricted diet was lower than that of the control and free amino acids diet. Using two-dimensional gel electrophoresis and mass spectrometry, we identified 16 differentially expressed protein spots in the jejunum of the weaning piglet. These proteins were related to stress and immune response, the metabolism of carbohydrates and lipids, and tissue structure. Based on the proteome and ELISA analysis, free amino acids diet significantly down-regulated the jejunal expression of stress protein heat shock 60 kDa protein. Our results indicated that amino acids supplementation to the protein restricted diet could enhance weight gain and feed efficiency in weanling pigs through improving intestinal nutrient absorption and transportation, gut health, and mucosal immunity.     

Dietary fiber decreases cholesterol and phospholipid synthesis in rat intestine

The effects of fiber ingestion on the incorporation of oleic acid into triglyceride and lecithin, acetate incorporation into cholesterol, and monosaccharide and amino acid transport were determined in rat intestine. Prolonged pectin (10% by weight) ingestion caused a decrease in jejunal and ileal cholesterol synthesis (33% and 52%, respectively). Pectin ingestion reduced cholesterol synthesis by 60% in ileal crypt cells, but did not affect cholesterol synthesis in the jejunal or ileal villus cells or in jejunal crypt cells. Cholesterol synthesis in isolated crypt cells was markedly less than in isolated villus cells. Prolonged ingestion of a fiber-free diet supplemented with either cellulose or pectin (10% and 5% by weight, respectively) decreased jejunal lecithin glucose and leucine absorption but did not affect jejunal triglyceride synthesis.     

Essential fatty acid deficiency affects the fatty acid composition of the rat small intestinal and colonic mucosa differently

The intestinal mucosal fatty acid (FA) composition was investigated in Sprague-Dawley rats after 7 and 23 weeks on an isocaloric diet with qualitatively different essential fatty acid (EFA) composition. For comparison, serum and red blood cell (RBC) membranes were investigated in parallel. The molar percentage of most FAs differed significantly between serum and RBC membranes both in controls and rats fed an EFA deficient (EFAD) diet. The influence of the EFA diet was similar on serum and RBC membrane phospholipids except for arachidonic acid (AA) which was more markedly decreased in serum than in RBC membranes. The FA composition was similar in ileal and colonic mucosa, markedly differing from the jejunal mucosa, in which the AA concentration was lower (13.0+/-0.8 versus 16.8+/-0.5 and 15. 7+/-2.8 mol%) and the linoleic acid (LA) concentration higher (34. 0+/-1.6 versus 17.8+/-1.3 and 15.5+/-2.8 mol%, respectively). The EFAD diet induced a more than five-fold decrease in the jejunal and ileal concentration of LA from 33.9+/-1.6 to 6.0+/-1.5 mol% and 17. 8+/-1.3 to 2.1+/-0.7 mol%, respectively. AA decreased more in the ileal and colonic mucosa than in the jejunum. The changes in the FA composition of the intestinal compartments after EFAD diet were different from that in serum and RBC membranes, and did not further change after 23 weeks compared to 7 weeks after introduction of the diet. The study shows that dietary influences are tissue specific and serum or RBC membranes do not mirror local changes in any of the different intestinal segments.     

Gamma radiation affects active electrolyte transport by rabbit ileum. II. Correlation of alanine and theophylline response with morphology

The response of ileal segments isolated from rabbits to an actively transported amino acid and a secretagogue was evaluated following exposure to 10 Gy whole-body gamma irradiation. The ability of ileal segments to respond to the actively transported amino acid, alanine, was not significantly diminished until 96 h postexposure. Decreased responsiveness to the secretagogue, theophylline, occurred earlier at 72 h. These effects did not appear to be accounted for by decreased food intake of irradiated animals alone. Examination of intestinal morphological changes with respect to these changes in electrolyte transport revealed that decreased amino acid transport coincides with loss of intestinal villi. Although a morphological correlate of decreased secretory response was not as striking as that for absorption, the theophylline response appeared to decline concomitant with the appearance of increased mitotic activity in the intestinal crypts. The results of this study indicate that, following a dose of 10 Gy, the inability of these tissues to respond to amino acids is due to a loss of mature villus absorptive cells subsequent to denudation of the intestinal mucosa. There appeared to be little impairment of cell membrane transport processes for alanine. In contrast, the decreased secretory response could not be correlated with the disappearance of any one cell type and perhaps results from increased proliferation in the crypts at the expense of differentiation.     

Bile acid uptake by isolated intestinal mucosa cells of guinea pig

Isolated intestinal mucosa cells of the guinea pig were employed to study intestinal transport of bile acids. Chenodeoxycholate and lithocholate were rapidly taken up into jejunal and ileal cells by diffusion. Taurocholate and cholate however showed only a minor diffusion rate and were preferentially taken up by the ileal bile acid carrier. This uptake was saturable with an apparent K_m of 231 μM and V of 7 nmol/mg protein per min for taurocholate; this bile acid was accumulated 90-fold. Its uptake was strongly inhibited by antimycin A, FCCP, ouabain or Na⁺-deficiency in the medium. Sugars or amino acids did not interfere with uptake. Experimental conditions were optimized with regard to incubation medium, cell amount, cell age and length of preincubation. It is concluded that ileal cells of the guinea pig are superior to other experimental models for characterizing the ileal bile acid carrier, because they allow us to determine initial rates of uptake and have a very efficient energetic coupling.