Sacs Of Everted Small Intestine Research Articles

Transport of citrate across the brush border and basolateral membrane of rat small intestine

It was the aim of the present study to investigate the transport of tricarboxylates (citrate, tricarballylate) across the basolateral membrane (BLM) of the small intestine. Experiments were performed using BLM vesicles isolated from the jejunum of rats. For comparison, some experiments with brush border membrane (BBM) vesicles were also performed. Finally, transfer of citrate and tricarballylate across the intestinal wall was investigated using sacs of everted small intestine. Uptake of citrate by BBM vesicles occurs by a Na + gradient-driven transport mechanism specific for tri- and dicarboxylates. The partially protonated forms of citrate seem to be much better transported than the completely dissociated form, since lowering the extravesicular pH from 7.8 to 5.6 resulted in a marked stimulation of Na +-dependent citrate uptake. In contrast to citrate uptake across the BBM, uptake of citrate across the BLM was neither influenced by Na 2+ nor by pH changes. Neither structurally related tri- and dicarboxylates (tricarballylate, succinate) nor other organic and inorganic anions (e.g. lactate, P-aminohippurate, sulfate, chloride, bicarbonate) significantly influenced citrate uptake by BLM vesicles under cis-conditions. Uptake of citrate as a function of the extravesicular substrate concentration was linear over a concentration range from 0.1 to 10mmol/l. Thus, citrate uptake under these conditions seems to be Na +-independent and not to be mediated by a carrier. However, preloading the BLM V with citrate clearly mi/is-stimulated the uptake of citrate and tricarballylate, respectively. Furthermore, citrate significantly inhibited tricarballylate uptake into BLMV preloaded with citrate. These results indicate uptake of tricarboxylates across the BLM by an exchange mechanism. Using sacs of everted small intestine, no transfer of intact citrate against a concentration gradient occurred, but some evidence for metabolization of citrate within the intestinal wall was obtained. In contrast, the non-metabolizable tricarboxylate tricarballylate was significantly accumulated in the serosal compartment of everted intestinal sacs.

Seasonal variations in intestinal uptake of nutrients in the Chilean lizard Liolaemus nitidus (Iguanidae). The effect of thyroxine (T 4)

Seasonal variations in d-glucose and l-tyrosine absorption were studied in everted sacs of small intestine of the Chilean lizard, Liolaemus nitidus. The absorption of d-glucose (10, 20 and 40 mM) and l-tyrosine (2 and 5 mM) increases significantly ( P < 0.05) during the summer compared with values from animals captured during the winter. Thyroxine (T 4) induced a significant ( P < 0.05) increase in d-glucose absorption in both seasons, and l-tyrosine during the winter, whilst the chemically thyroidectomized (PTU) lizards showed very low absorption capacity for both compounds. The seasonal changes in intestinal uptake of glucose and tyrosine shown by L. nitidus are related to levels of thyroxine during the summer and the winter.

Heavy metal-induced inhibition of active transport in the rat small intestine in vitro. Interaction with other ions

1. 1. The effect of Hg 2+, Cd 2+ and Pb 2+ on the intestinal transport of d-glucose and l-tyrosine was studied in everted sacs of small intestine. 2. 2. Hg 2+, Cd 2+ and Pb 2+ (10 −5 and 10 −4) singly or in combination inhibit the active transport of d-glucose (10mM) and l-tyrosine (2mM) in rat and pigeon small intestine. 3. 3. The presence of other ions (Mg 2+, Zn 2+ and SeO 3 2) diminishes the toxic effect of heavy metal ions, rendering them less effective.

Intestinal absorption mechanisms of gamma-butyrolactone-gamma-carbonyl-L-histidyl-L-prolinamide citrate (DN-1417) and thyrotropin-releasing hormone (TRH).

The absorption mechanisms of gamma-butyrolactone-gamma-carbonyl-L-histidyl-L-prolinamide citrate (DN-1417) and thyrotropin-releasing hormone (TRH) were studied in the rat. In situ absorption experiments were carried out by the radioimmunoassay, and experiments using everted sacs of small intestine were by radioactivity measurements with 14C-labeled DN-1417 or 3H-labeled TRH in the low concentration range of drug and by a high pressure liquid chromatography in the rather high concentration range of drug. The site specificity of absorption in the small intestine of rats could not be found with DN-1417, whereas TRH-T was absorbed from only the upper part of small intestine. Dose-proportional absorption of DN-1417 was observed in experiments of in situ as well as in vitro. Dose-proportional transfer of DN-1417 through the everted small intestine was also found within the concentration range from 120 ng/ml to 27 mg/ml, whereas the transfer ratio of TRH decreased with increase in the concentration of TRH. DN-1417 transfer from mucosal to serosal fluid was not inhibited by the replacement of medium Na ions by K ions, pretreatment of intestinal mucosa with HgCl2, the existence of an oligopeptide, or the existence of beta-lactam antibiotics which had been reported to be absorbed by active transport or carrier-mediated transport systems. While, TRH transfer was inhibited by the replacement of medium Na ions by K ions, pretreatment of intestinal mucosa with HgCl2, the existence of an oligopeptide, and the existence of beta-lactam antibiotics.(ABSTRACT TRUNCATED AT 250 WORDS)

Sites of dipeptide hydrolysis in relation to sites of histidine and glucose active transport in hamster intestine.

The effects of dipeptides and amino acids on the active transport of L-histidine and D-glucose by sacs of everted small intestine of the hamster have been used to determine the sites of final hydrolysis of the dipeptides in relation to the sites of active transport of L-histidine and D-glucose. The results, plus earlier observations (Wiseman, 1977), show that (a) dipeptide active transport occurs at a superficial site, followed by progressively deeper sites for (b) final hydrolysis of glycyl-phenylalanine and phenylalanyl-glycine, then deeper (c) L-histidine active transport, then (d) final hydrolysis of alanyl-alanine, alanyl-leucine, glycyl-alanine, glycyl-proline, leucyl-alanine and leucyl-leucine, then (e) D-glucose active transport, then (f) final hydrolysis of alanyl-glycine, alanyl-valine, glycyl-glycine, prolyl-glycine, valyl-alanine and valyl-valine. The site of D-glucose active transport (2e) and all the sites superficial to it (2a-d) lie in the intestinal epithelial cell's brush-border. The location within the cell of site(s) 2f is not known; it may lie in the cytosol. All the dipeptides appeared to inhibit L-histidine active transport by the release of free amino acid and not by action of intact dipeptide, supporting the view that dipeptides and free amino acids do not share a common transport pathway in the epithelium of the small intestine.

Inhibition of the active transport of d-glucose and l-tyrosine by DDT and DDE in the rat small intestine

1. The effect of DDT and DDE on the active transport of d-glucose and l-tyrosine was studied in everted sacs of small intestine. 2. DDT and DDE (10 −5 and 10 −4 M) inhibit the active transport of d-glucose and l-tyrosine. 3. These organochlorine compounds also inhibit the (Na + + K +)-ATPase from the same tissue, to about the same extent. 4. These results suggest that the inhibition of the active transport is due to an action of DDT and DDE on the sodium pump.

Site of intestinal dipeptide hydrolysis.

1. Sacs of everted small intestine of the hamster have been used to study the site of final hydrolysis of twelve dipeptides. 2. The results suggest that L-alanyl-glycine, glycyl-glycine, L-valyl-L-valine, L-alanyl-L-valine, L-valyl-L-alanine and L-prolyl-glycine are hydrolysed beyond the locus of the active transport mechanism for D-glucose, perhaps even within the cell. These may be designated class 1 (deep) dipeptides. 3. In contrast, superficial (perhaps even surface) hydrolysis seems to occur with L-alanyl-L-alanine, L-leucly-L-leucine, glycyl-L-alanine, L-alanyl-L-leucine, L-leucyl-L-alanine and glycyl-L-proline. These may be designated class 2 (superficial) dipeptides. 4. All the dipeptides were able to partially inhibit D-glucose active transport, the findings supporting the view that more than one mechanism may exist for the active absorption of the sugar.

Developmental changes of sugar transport in the ovine small intestine.

Intestinal monosaccharide transport was studied in young lambs (age: up to 1 week) and in older lambs (age: 2.5-4 months) with well developed forestomach system employing everted sacs of small intestine. Both glucose and galactose were transported against a high concentration gradient from the mucosal to the serosal side of the intestinal wall in young lambs. In the older lambs glucose was transported only against a small concentration gradient, when intestinal glucose metabolism was diminished by reducing the pH of the incubation medium from 7 to 5. Galactose and alpha-methyl-glucoside, which are not markedly metabolized by the intestine, were transported against a small but similar concentration gradient at both pH values in these animals. In young lambs, however, at pH 5 intestinal galactose transport was lower than at pH 7. These results indicate that active intestinal monosaccharide transport becomes rudimentary in the maturing sheep.

Transfer of alanine isomers by rat small intestine.

1. A study was made of the transfer of L-alanine, D-alanine and beta-alanine by sacs of everted small intestine of the rat.2. D-Alanine and beta-alanine are transported against a concentration gradient and in this respect resemble L-alanine.3. Transfer of all three isomers was stimulated in presence of glucose, but stimulation was much greater with D-alanine and beta-alanine.4. Transfer of all three isomers was inhibited by galactose.5. The effect of hexoses on amino acid transfer was relatively independent of the effect on fluid transfer.6. L-Methionine inhibited transfer of the three isomers in descending order, L-alanine, D-alanine and beta-alanine, while the magnitude of sarcosine inhibition was in the reverse order.7. At the concentration used (1 mM), L-alanine was transferred mostly by the methionine carrier, and beta-alanine mostly by the sarcosine carrier. D-Alanine occupied an intermediate position.

Transport of the amino acids, 1-amino cyclopentane-1-carboxylic acid and ε-aminocaproic acid, across intestinal mucosa in vitro

Two α-methyl substituted amino acids, 1-amino cyclopentane-1-carboxylic acid (ACPC), and isovaline, are actively transported across everted sacs of small intestine from the rat. ACPC inhibits growth of the Walker rat carcinoma. The antifibrinolytic amino acid, ε-aminocaproic acid (EACA), was not actively transported at therapeutic concentrations. These studies are relevant to the design of pharmacologically active amino acids or their analogues which may be introduced into cells by an active process rather than by passive diffusion.

Ammonia movement in the small intestine: preferential transport by the ileum.

Isolated, surviving sacs of everted small intestine were used to characterize ammonia transport in the golden hamster. Jejunal and ileal sacs incubated aerobically in ammonia-free test solution liberated the same quantity of ammonia as did sacs that were filled and immediately emptied of their contents, indicating no significant evolution of metabolic ammonia. Under aerobic conditions, ileal sacs transferred a solution of high ammonia content from the mucosal surface to the serosal surface against a concentration gradient. This transport was not glucose dependent and exhibited first-order Michaelis-Menten kinetics. Inhibition of absorption occurred with anaerobiosis, 2,4-dinitrophenol, and sodium cyanide. In jejunal segments ammonia was not transported against an adverse chemical gradient. Ileal ammonia absorption was accompanied by bicarbonate secretion and acidification of the serosal solution. Both bicarbonate movement and pH gradients were abolished by inhibitors of ammonia transport. In the jejunum, the absence of ammonia movement occurred in association with minimal bicarbonate secretion and no appreciable change in serosal pH. Despite the creation of hydrogen ion gradients tending to augment or to retard ammonia absorption by nonionic diffusion, ammonia movement was unaffected, i.e., relative acidification of serosal contents did not augment ammonia absorption, and relative alkalinization of serosal fluid caused no inhibition of ammonia transport. In the absence of bicarbonate ion, ammonia transport did not occur. The significance of these findings is discussed with consideration of both ionic and nonionic mechanisms of ammonia movement. It is suggested that ammonia is absorbed in the ileum by active ionic transport.

Studies on the active transport of D-glucose and L-histidine by rats and golden hamsters fed on a penicillin-enriched diet.

1. The effect of a penicillin-enriched diet (100 mg or 1000 mg penicillin-G/kg food) on the active transport of D-glucose and L-histidine has been investigated by the use of sacs of everted small intestine of normal young adult rats and golden hamsters. The antibiotic was given for up to several weeks.2. The penicillin made no difference to the final concentration gradients of D-glucose or L-histidine achieved by rat small intestine, although with the hamster these appeared somewhat improved. Water entry into the serosal fluid remained unchanged.3. The lengths and the dry weights of the small intestines of both species were not altered by the dietary regimen.

Further studies on intestinal active transport during semistarvation.

1. The effect of semistarvation (sufficient to produce a loss of 18-28% of initial body weight) on the active transport of D-glucose and L-histidine by the rat, the guinea-pig and the golden hamster has been investigated by the use of sacs of everted small intestine (from upper jejunum to lower ileum).2. In the rat and the guinea-pig the dietary restriction resulted in increased active transport in all regions of the small intestine. In contrast, it caused no alteration in active transport in the hamster.3. The response in the rat was most impressive in the middle-to-lower ileum during D-glucose uptake. Whereas normal sacs from this area appeared unable to move the sugar against its concentration gradient, sacs from semistarved rats did so quite well.4. Although there was a considerable loss (24-29%) of intestinal dry weight in all three species when the food intake was reduced, shortening of the small intestine was not detectable in the guinea-pig or the hamster and was present to only a minor extent in the rat.5. Evidence is presented indicating that the enhanced active transport is not merely a reflexion of the thinning of the intestinal wall and that it occurs during complete as well as in partial starvation.

The effect of amino acids on the intestinal transport of L- and D-xylose in vitro.

1. The intestinal transport of D-xylose by sacs of everted small intestine of the hamster is partially inhibited by L-histidine in concentrations of 5, 10 and 20 mM but not of 2 mM.2. 20 mM concentrations of D-histidine and L-methionine also produce inhibition.3. The inhibition is not due to an alteration in water transport or to a change in pH of the incubating medium.4. The rate of the intestinal transport of L-xylose is about (1/4) of the rate of D-xylose transport and is unaffected by a 20 mM concentration of L-histidine.

Effect of glucagon on transfer of glucose, utilizing everted sacs of small intestine.

The effect of glucagon on intestinal transference of glucose was studied utilizing everted sacs of small intestine of rat and hamster. All experiments were performed under aerobic conditions in Warburg flasks at 37°C for a period of 1 hour. Quantitative estimations were made of the amount of glucose transferred and metabolized by these sacs. It was observed that glucose is transferred against a concentration gradient with relatively little movement of water and that a considerable portion of the glucose metabolized appears as lactic acid. It was apparent that under these experimental conditions glucagon exerts no observable influence on the transfer of glucose by rat and hamster small intestine. The mechanism through which glucagon inhibits gastric secretory activity continues to be unknown.

Factors controlling B12 uptake by intestinal sacs in vitro.

Sacs of everted small intestine were incubated in bicarbonate-saline containing radioactive vitamin B12 with or without a source of gastric intrinsic factor (IF). In both the hamster and guinea pig the lowest ileum was most active in B12 uptake in the presence of intrinsic factor, the upper jejunum showing little or no uptake. Low temperature and anaerobic conditions completely abolished the stimulatory effect of IF on B12 uptake. Intrinsic factor did not bind to the intestinal wall in the absence of B12 (even in the presence of calcium ion) as the IF activity could be completely removed by gentle washing of the tissue. The vitamin and intrinsic factor must be present together to cause intestinal uptake of B12.

Some species differences in the intrinsic factor stimulation of B12 uptake by small intestine in vitro.

Sacs of everted small intestine from a variety of animals were incubated in bicarbonate-saline containing vitamin B12 with and without intrinsic factor (IF). B12 uptake by rat intestine was stimulated only by its own intrinsic factor. Guinea pig ileum responded to all intrinsic factors tested (guinea pig, rat, hog, hamster, human being and rabbit). The intestines of hamster and rabbit were intermediate in specificity, responding to some, but not all, of the IF preparations. Species differences occur in both the intestine and intrinsic factor preparations. The guinea pig ileum was suggested as a possible assay for both hog and human IF.

Effects of Salicylate on the Metabolic Activity of the Small Intestine of the Rat

The effects of salicylate on the transfer of glucose, sorbose and fluid across the intestinal wall and on the respiration, glycolysis and histological structure of sacs of everted small intestine from the rat, incubated under aerobic conditions, have been studied. 5 mm salicylate was found to inhibit the active transport of glucose and fluid, to increase the passive diffusion of sorbose, to decrease the oxygen uptake, to cause structural damage to the columnar epithelium lining the villi of the intestine, but not to affect the aerobic glycolysis of the sacs. It was concluded that the salicylate interfered with normal respiratory processes and hence with the supply of energy necessary for active transport processes in the intestinal preparation. The increased permeability of the sacs to sorbose may have resulted from the epithelial damage caused by the salicylate.

Active transport of amino acids by sacs of everted small intestine of the golden hamster (Mesocricetus auratus)

Active transport of amino acids by sacs of everted small intestine of the golden hamster (<i>Mesocricetus auratus</i>)

Preferential transference of amino-acids from amino-acid mixtures by sacs of everted small intestine of the golden hamster (Mesocricetus auratus).

The Journal of PhysiologyVolume 127, Issue 2 p. 414-422 ArticleFree Access Preferential transference of amino-acids from amino-acid mixtures by sacs of everted small intestine of the golden hamster (Mesocricetus auratus) G. Wiseman, G. WisemanSearch for more papers by this author G. Wiseman, G. WisemanSearch for more papers by this author First published: 28 February 1955 https://doi.org/10.1113/jphysiol.1955.sp005267Citations: 83AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Citing Literature Volume127, Issue2February 28, 1955Pages 414-422 RelatedInformation