Alanine Absorption Research Articles

Effect of mimosine on portal-drained visceral net flux and concentrations of amino acids and minerals in plasma of Alpine goats

This experiment was designed to investigate whether circulating mimosine imposes limitations on absorption of amino acids and minerals from the gastrointestinal tract of Alpine goats. Circulating mimosine, portal blood and plasma flow rate, and concentrations and net absorption of amino acids and minerals were measured 60 h before (PRE) and 24 h after (POST) the femoral vein infusion of mimosine (12.5 mg kg −1 BW −0.75 h −1). Mimosine infusion did not affect portal plasma flow rate. Venous and arterial plasma amino acid and mineral concentrations were depressed and the absorption of alanine ( P < 0.09), serine ( P < 0.04) and methionine ( P < 0.03) from the gastrointestinal tract were reduced for up to 24 h after the cessation of mimosine infusion, even when normal feeding was resumed. This disruption was possibly caused by the circulating mimosine (4.88 μm 1 −1 during POST) directly, via chelation or competition for absorption, or, indirectly, by gastrointestinal lesions resulting from circulating mimosine. Pivotal to this experiment was the observation that mimosine was eliminated from the goat circulatory system approximately 40 times more rapidly in a 24 h period than when similar concentrations were infused in sheep.

Involvement of capsaicin-sensitive primary afferent fibers in regulation of jejunal alanine absorption

Capsaicin-sensitive primary afferent fibers (CSPA) in the small intestine regulate many functions through the release of peptides and neurotransmitters. This study was undertaken to assess the role of CSPA in the regulation of jejunal alanine absorption in the rat. In a series of in vivo experiments, the effects of the sensory neurotoxin capsaicin on small intestinal alanine absorption were evaluated. In vitro experiments were also done to study its effects on alanine uptake by isolated jejunal strips and mucosal scrapings. Jejunal alanine absorption was reduced by 27% when capsaicin (160 and 800 microM) was perfused intraluminally and by 21% when it was applied topically to the cervical vagi. On the other hand, bilateral cervical vagotomy and reversible block of vagal CSPA increased alanine absorption by 29 and 41%, respectively. In vitro, capsaicin reduced alanine uptake by intestinal strips in a dose-dependent manner. Maximal inhibition (36.5%) occurred at 400 microM with the mean ineffective concentration at 87 microM. Alanine uptake by jejunal mucosal scrapings, however, was decreased only by 6.7% when incubated with 1,600 microM capsaicin. These data suggest that vagal CSPA exerts a tonic inhibitory effect on alanine absorption and that capsaicin's inhibitory effect on alanine absorption is mediated largely by the capsaicin-sensitive afferent fibers.

Effect of L-alanine and ouabain on membrane conductances and apical membrane potential in Aplysia intestine

The proximal intestine of Aplysia californica was employed to assess the effect of alanine absorption on apical membrane K+ conductance (GKa) and basolateral membrane conductance (Gb) and the role of the electrogenic Na(+)-K(+)-adenosinetriphosphatase (Na+ pump) in the repolarization of apical membrane electrical potential difference (Va) after alanine-induced depolarization. Addition of 50 mM L-alanine (isosmotic substitution for mannitol) to the apical superfusate depolarized Va, reduced the ratio of apical to basolateral membrane resistances (Ra/Rb), and stimulated short-circuit current (Isc). Following these initial events, Va repolarized, Ra/Rb increased, and there was a slight decline in Isc. Apical high-K+ artificial seawater revealed an alanine-induced increase in GKa. Washout of alanine from the apical solution increased Ra/Rb above the prealanine control value. Thus alanine absorption is accompanied by an increase in Gb. Basolateral 0.1 mM ouabain abolished alanine-stimulated Isc but had little effect on Va ( < 3 mV depolarization) either before or after exposure to alanine. The repolarization of Va was not affected in tissues superfused with 0.1 mM basolateral ouabain for approximately 3 min even though the alanine-stimulated increase in Isc was abolished. Therefore, the electrogenic Na+ pump contributes minimally to the repolarization of Va in sea hare intestine. The origin of the hyperpolarization of Va resides therefore, at least in part, in the increase in GKa, which restores the driving force for Na(+)-alanine cotransport and prevents K+ accumulation in the enterocytes.

Capsaicin's inhibition of alanine (ALA) absorption in the rat jejunum is neurally mediated and involves a decrease in the affinity for alanine absorption

Capsaicin's inhibition of alanine (ALA) absorption in the rat jejunum is neurally mediated and involves a decrease in the affinity for alanine absorption

Effects of intravenous vasoactive intestinal peptide injection on jejunal alanine absorption and gastric acid secretion in rats

The effect of intravenous vasoactive intestinal polypeptide (VIP) injection on jejunal l-alanine absorption and gastric acid secretion in the rat was investigated. Continuous intravenous VIP infusion (11.2 ng/kg per min) throughout the experimental period (160 min) produced 60% decrease in alanine absorption and 40% decrease in gastric acid secretion during the second hour of the experiment. Subdiaphragmatic vagotomy reduced alanine absorption to 91% ( P>0.05) and 71.3% ( P<0.05) of control value during the first and second hours of perfusion, respectively. VIP infusion following vagotomy elicited a reduced effect when compared to that produced by similar injections in normal rats. Gastric secretion in vagotomized rats was reduced by 40% ( P<0.05) below control. VIP infusion in vagotomized rats exerted a significant decrease ( P<0.05) of gastric acid secretion. Moreover, water absorption was decreased by almost 10% ( P<0.05) after i.v. injection of VIP and was increased by 20–24% above control value following vagotomy. However, i.v. administration of VIP following vagotomy did not elicit any further change in water absorption. It can be concluded that VIP inhibits alanine absorption and gastric acid secretion in the rat and that these inhibitory effects might be partially mediated by the vagus nerve.

Effects of intracerebral injections of VIP on jejunal alanine absorption and gastric acid secretion in rats

The effects of intracerebral injections of VIP on jejunal alanine absorption and gastric acid secretion, and its association with vagal outflow were examined in Sprague-Dawley rats. Intracerebroventricular injection of VIP (2 ng) decreased significantly ( P<0.05) alanine absorption across the jejunum, whereas similar injections in vagotomized rats did not show further decrease in absorption beyond that noticed by vagotomy only. Moreover, VIP injected in the Nucleus Tractus Solitarius-Dorsal Motor Nucleus (NTS-DMN) complex (1 ng) produced also a significant inhibition of Ala absorption which was reduced but remained significant ( P<0.05) after vagotomy. Water movement was not affected by VIP injection in the lateral ventricle, while VIP injections in the NTS-DMN inhibited significantly ( P<0.05) jejunal water absorption by 10–12%. Vagotomy increased water absorption by 15–20% above control ( P<0.05) which was not altered by injecting VIP in the NTS-DMN complex. On the other hand, VIP injection in the NTS-DMN produced a 25.7% increase in gastric acid output in the first hour of the experiment followed by a non-significant decrease ( P>0.05) in the second hour. Same injections done in vagotomized animals produced similar effects to those elicited by vagotomy only. It can be suggested that NTS-DMN complex could be a site of action of VIP since injection of VIP in it produced a more pronounced inhibitory effect on water and Ala absorption than that produced by VIP injection in the LV. These effects were reduced or abolished by vagotomy. It is concluded that when VIP is injected in the brain and in particular in the NTS-DMN complex, it can modulate intestinal absorption and gastric secretion, and this modulation is mainly exerted through the vagal outflow.

Functional and structural changes in the jejunum of the rat following cysteamine and stress-induced duodenal ulcer.

The effects of cysteamine and stress-induced duodenal ulcer on the functional and structural properties of the rat jejunum were investigated. The absorptive capacity of the jejunum was determined using alanine as the permeant solute and the single-pass perfusion technique. A statistically significant decrease (p < 0.01) in alanine absorption was observed after 8 h and 3 days of duodenal ulcer induction by stress and cysteamine respectively. However, alanine transport measured 7 days after cysteamine or stress ulcer induction showed no significant change from control values. Cysteamine and stress-induced duodenal ulcer did not show any significant change in water absorption across the jejunum when measured after 8 h, 3 and 7 days of ulcer induction. Microscopically, the jejunum of rats with 3-day cysteamine-induced ulcer exhibited diffuse type of apical derangements with excessive swelling of the villi and progressive degenerative changes. No such changes were noticed on the 7th day nor in the jejunum of the rats with stress-induced duodenal ulcer. The results suggest that cysteamine-induced duodenal ulcer produces an inhibition in the absorptive capacity of the jejunum which is time-dependent and reversible.

Interaction of Z-4,4-Bis(4-Ethylphenyl)-2,3-Dibromo-2-Butenoic Acid with Amino-Transferases: Changes in Absorption and Circular Dichroism Spectra

The influence of Z-4,4-bis(4-ethylphenyl)-2,3-dibromo-2-butenoic acid, the compound originally synthetized as a cytostatic edikron and showing inhibitory effect on several pyridoxal enzymes, on absorption and circular dichroism spectra of alanine and aspartate aminotransferases (ALT, AST) in the region of coenzyme absorption characteristics was studied. In the case of AST, the compound decreased absorption and CD maxima at 360 nm, which represents the active form of the enzyme, but it did not seem to prevent formation of the pyridoxamine form of the enzyme, produced in the presence of L-aspartate. Edikron caused insignificant spectral changes of ALT, but it partially denatured the enzyme. Circular dichroism measurement of both enzymes uncovered some effects of edikron at 250-300 nm, which suggests conformational changes in the aromatic amino acids of the apoenzymes due to the compound studied.

Glucose and alanine absorption following massive small bowel resection.

A 90% small bowel resection in 8 dogs resulted in a significant decrease (p less than 0.05) in D-xylose and D-glucose absorption during the early postoperative period. The absorptive capacity of the residual gut with regard to L-alanine, however, remained unchanged. Anemia and hypoalbuminemia also occurred in time, suggesting a malabsorptive state. Control studies were performed in 8 dogs with small bowel transections. The results suggest that a high protein diet might be of benefit during the early postoperative period after massive small bowel resection.

Segmental small intestinal allografts in the dog. I. Morphological and functional indices of rejection.

Fourteen dogs received an orthotopically vascularized allograft of a 100-cm length of terminal ileum as a Thiry-Vella segment. Absorption, motility, myoelectrical activity and morphology of the allograft were studied to determine the most reliable indices of rejection. The earliest histological evidence of rejection occurred at a mean of 6.2 +/- 0.9 days and was coincident with significant deterioration in the absorption of water, alanine, lauric acid, sodium, and glucose. Intestinal motility did not decrease until 7-8 days after transplantation, and intestinal myoelectrical activity was unchanged for a further 2-3 days, by which time graft necrosis was imminent. Reduced intestinal motility occurs only after rejection is established, and is therefore of little use as an index of rejection, while recording intestinal myoelectrical activity is valueless and serves only to confirm graft death. Decreased intestinal absorption of water, sodium, glucose, alanine, and lauric acid are present as early as the first changes in mucosal histology and are useful indices of rejection of intestinal allografts.

Functional significance of histologic alterations induced by Escherichia coli pig-specific, mouse-negative, heat-stable enterotoxin (STb).

In contrast to cholera enterotoxin and other Escherichia coli enterotoxins, a pig-specific, heat-stable E. coli enterotoxin (STb) causes morphologic lesions (loss of villous epithelial cells and partial villous atrophy). These lesions reflect a loss of absorptive cells and thus suggest that STb causes impaired absorption as well as inducing net secretion. The present studies assess functional significance of morphologic changes induced by STb. Net fluid movement, mucosal surface area, sucrase activity and the electrical response induced by alanine were measured in swine jejunal loops exposed to E. coli culture filtrates with and without STb. Net fluid secretion (-11.1 +/- 1.1 ml) occurred in some STb loops (secretors) and net absorption (2.7 +/- 0.3 ml) in others (nonsecretors), but net absorption occurred in all control loops (4.9 +/- 0.2 ml). The mucosal surface area of STb loops was about 20% less than that of controls (P less than 0.01). Sucrase activity was also lower (about 15%) in STb loops than in control loops (P less than 0.01). The electrical response induced by alanine in mucosa from nonsecreting STb loops did not differ from that induced in mucosa from control loops. However, the response to alanine in mucosa from secreting STb loops was reduced about 70% from that in mucosa from nonsecreting STb loops or from control loops (P less than 0.05). It is concluded that reduced sucrase activity is a functional correlate to villous atrophy induced by STb, that STb impairs alanine absorption in some loops (secretors), and that the impaired alanine absorption is independent of the decreased surface area caused by STb. Because the impaired alanine absorption occurred independent of the decreases in surface area, it is suggested that the secretory response to STb is associated with an impairment of active absorption of alanine.

Effect of a single oral dose of pp'DDT on the absorption of nutrients in vitro and on brush border enzymes in rat intestine.

The effect of a single oral dose of pp'DDT (100 mg/kg body wt.) has been studied on the intestinal uptake of certain nutrients and on brush border enzymes in rats. Intestinal uptake of leucine, and phenylalanine was considerably increased but there was no change in the absorption of glucose and alanine in DDT fed rats, compared to controls. The activities of brush border sucrase, alkaline phosphatase and Na+, K+-ATPase were significantly depressed in pesticide treated animals, but leucine aminopeptidase levels remained unaffected under these conditions. Analysis of the chemical composition of the microvillus membranes revealed a considerable enhancement in total lipids, phospholipids and triglyceride contents of the membranes in DDT exposed rats, but membrane protein, sialic acid and cholesterol fractions did not record any change. 1-14C-acetate incorporation into various lipid classes was studied to explain the observed increase in membrane lipids in DDT exposed animals.

Mechanism of inhibition of alanine absorption by Na ricinoleate.

The mechanism of inhibition of alanine absorption by Na ricinoleate has been examined in the rabbit intestine. This fatty acid in a concentration of 2--5 mM inhibits alanine absorption in vivo and in vitro. The inhibition is more evident in the jejunum than in the ileum. Strips of ileal mucosa treated with Na ricinoleate gain Na. Sodium ricinoleate inhibits alanine influx across rabbit ileum, even in the presence of a sodium gradient across these cells. The results suggest that the main action of Na ricinoleate is on the alanine-transport system at the brush-border membrane. The fatty acid may also inhibit amino acid absorption by increasing intestinal cell Na concentration, which results in a decreased Na gradient across the brush-border membrane.

Sodium, phosphate, glucose, bicarbonate, and alanine interactions in the isolated proximal convoluted tubule of the rabbit kidney.

Interactions among the transport systems involved with sodium, bicarbonate, glucose, phosphate, and alanine absorption in isolated segments of the rabbit proximal convoluted tubule were examined with radioisotopic techniques to measure glucose, phosphate, and fluid absorption rates. The composition of the perfusate and bath varied from normal, physiological fluids to fluids deficient in a single solute. The deletion of glucose from the perfusate increased the lumen-to-bath flux of phosphate from 5.51 +/- 1.15 to 8.32 +/- 1.34 pmol/mm-min (P less than 0.01). Similar changes occurred when glucose transport was inhibited by phlorizin 10 micron in the perfusate, The deletion of alanine from the perfusate increased the lumen-to-bath flux of phosphate from 6.55 +/- 1.08 to 9.00 +/- 1.30 pmol/mm-min (P less than 0.01) but did not affect glucose transport significantly, 80.1 +/- 10.1 vs. 72.5 +/- 5.4 pmol/mm-min. Replacement of intraluminal sodium with choline, elimination of potassium from the bath, and removal of bicarbonate from the lumen and bath each reduced glucose, phosphate, and fluid absorption. These data indicate that the proximal absorptive processes for glucose and for phosphate include elements that are dependent upon some function of sodium transport. Additionally, the effects on phosphate transport of deleting glucose or alanine occur independent of any changes in net sodium transport and are opposite the effects of deleting bicarbonate. These differences may relate to the observations that the transport of glucose and alanine is electrogenic while that of bicarbonate is not. Regardless of possible mechanisms, the data demonstrate that important changes in the absorption rates of different solutes handled significantly by the proximal convoluted tubule may occur in response to changes in specific components of proximal sodium transport.

Effect of bile salts on amino acid transport by rabbit intestine.

The effect of bile salts on alanine absorption across four regional sites of rabbit intestine was examined using an in vivo single-pass perfusion technique. Na-deoxycholate at a concentration of 3 mM reduced alanine absorption across all levels of the intestine, and a higher concentration (10 mM) of Na-taurodeoxycholate (TDC) caused only a minimal reduction of alanine absorption in the jejunum. TDC, however, was more effective in in vitro experiments, causing an incrase in transmural serosal-to-mucosal flux of alanine and phenylalanine, particularly when present in both the mucosal and serosal media. It also reduced the mucosal-to-serosal alanine flux rate when present only in the mucosal medium. The influx of these amino acids across the mucosal brush border membrane was also decreased by TDC. These amino acid transport changes correlated fairly well with some observed histological changes of the intestinal epithelium. This suggests that bile salt inhibition of amino acid absorption is nonspecific in type and can be mainly explained as being the result of an injurious action of these surface-active agents on the rabbit intestine.

Kinetics of alanine uptake by the gills of the soft shelled clam MYA arenaria

Abstract 1. An in vitro preparation of gill segments of Mya arenaria was used to examine the kinetics of L - and D -alanine absorption. 2. The preparation was shown to be viable. 3. Both enantiomorphs of alanine were absorbed against a concentration gradient and in 60 min little breakdown or incorporation of the L -enantiomorph occurred in the tissue. 4. Uptake of both L - and D -alanine followed saturation kinetics and at least two pathways were concerned in the absorption of the L form only one of which is shared with the D form. 5. Uptake of L -alanine was Na+ dependant and sensitive to the metabolic inhibitors NaCN and 2,4 DNP, and to the cardiac glycoside ouabain after pre-incubation. 6. The results are discussed in relation to amino acid transport systems in other animals.

Regional variation in alanine absorption in the gut of Echinus esculentus

1. 1. An in vitro preparation of Echinus esculentus gut was used to study the regional variation in oxygen consumption and alanine absorption. 2. 2. The oesophagus, stomach and intestine consumed oxygen at constant rates for at least 1 hr; the QO 2's for the oesophagus and stomach were similar while the QO 2 for the intestine was higher. 3. 3. l-Alanine was absorbed actively by all three regions and the values of K t and V max for each region appeared to be related to substrate availability in vivo. 4. 4. Prolonged exposure to metabolic inhibitors failed to reduce l-alanine absorption by the stomach. 5. 5. The carrier mechanism for alanine was stereospecific showing preference for the l-enantiomorph. 6. 6. Interference experiments indicated that the neutral amino acids d-alanine and l-leucine competitively inhibit l-alanine transport. 7. 7. The importance of regional variations in alanine absorption is discussed in relation to the mechanisms of digestion and absorption in Echinus gut.

Distinct components of neutral amino acid transport in chick small intestine

1. 1. The intestinal absorption of alanine, β-alanine, α-aminoisobutyric acid (AIB), glycine, proline and tryptophan has been studied by an in vitro tissue accumulation method in the chick. 2. 2. The use of amino acids as specific blocking agents allowed for the characterization of seven discrete components of neutral amino acid transport which can be grouped into three major categories: (a) those processes inhibited by leucine and glycine; (b) those inhibited by leucine, but not by glycine; (c) those not inhibited by leucine.

Sodium dependency of L-alanine absorption in canine Thiry-Vella loops.

The effect of sodium on the absorption of L-alanine in vivo was tested by measuring the absorption of L-alanine from Thiry-Vella loops in dogs. Solutions containing L-alanine (10 or 50 mM) sodium at concentrations of 0, 74, or 145 m-equiv/1 and mannitol, as needed to maintain isotonicity were instilled into the loops for 10 minutes. Similar studies were done with L-alanine 50 mM and either 0 or 145 m-equiv/1 of sodium for five minutes. Under all conditions absorption of alanine was significantly less from the solution initially free of sodium. Although these differences were statistically significant, the physiological significance was not great since the actual differences in amounts of L-alanine absorbed were small. Insorption of sodium was low from the fluid which initially had no sodium, but exsorption proceeded rapidly and was unaffected by the luminal sodium concentration. This resulted in a rapid rise of intraluminal sodium concentration when no sodium was initially present. This persistent exsorption of sodium was, therefore, adequate to provide sodium in the lumen to activate the sodium-dependent carrier, postulated on the basis of studies in vitro. These data in vivo are consistent with the view that sodium at the intraluminal surface is important in accelerating amino acid transport, but indicate that in the absence of added intraluminal sodium the gut mucosa itself, under normal circumstances, provides the sodium needed for L-alanine absorption.

Effect of Preloading on Alanine Absorption by Wheat Roots

AbstractStudying the amino acid absorption by higher plants we observed a stimulation of 14C‐alanine absorption by wheat roots preloaded with inactive alanine. Within the limits of concentration examined the increase of stimulation is more likely to depend on the free alanine content of the roots than on the alanine concentration of the solutions used for pretreatment. The stimulation is retained even after incubating the pretreated roots in diluted CaSO4 solution before the uptake period. Besides the alanine only the glycine gave stimulation, while pretreatment with valine, arginine or aspartic acid gave an inhibition. (The aspartic acid is likely to cause a general rise in the permeability of cells.)We suppose that the phenomenon of flow driven by counterflow is likely to serve as an explanation to the stimulatory preloading effect observed in the alanine absorption by wheat roots.