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PubMed2005

Relationship between glucose transporter and changes in the absorptive system in small intestinal absorptive cells during the weaning process.

In the present study, we investigated the changes in the localization of the glucose transporter GLUT2 and the fructose transporter GLUT5 in small intestinal absorptive cells during postnatal development, especially during the weaning period, using immunohistochemistry and confocal laser scanning microscopy. In the jejunum, GLUT2 was observed within the apical and basolateral membrane domain of absorptive cells, especially in the middle part of the villi. In the suckling rat ileum, GLUT2 was found within the apical and basolateral membrane domain of absorptive cells, but after 18 or 19 days after birth, GLUT2 was found mainly within the apical membrane domain. GLUT5 was observed within the apical membrane domain of absorptive cells in the suckling rat jejunum. In the 18- or 19-day-old rat jejunum, GLUT5 was localized within the apical and basolateral membrane domain of absorptive cells in the lower part of the villi, but after weaning, GLUT5 was found within the apical and basolateral membrane domain of absorptive cells throughout the entire villi. In the suckling rat ileum, there was little GLUT5 in the absorptive cells. In the 18- or 19-day-old rat ileum, GLUT5 was localized within the apical membrane domain of absorptive cells in the lower part of the villi, but after weaning, GLUT5 was observed mainly within the apical membrane domain of absorptive cells throughout the entire villi. These results suggest that the localization of glucose transporters corresponds with a shift from neonatal-suckling to weaned absorptive cells during postnatal development.

Absorption↗
PubMed1994

Inhibition of short-chain fatty acid absorption and Na+ absorption during acute colitis in the rabbit.

BACKGROUND/AIMS: Short-chain fatty acids (SCFAs) provide energy for colonocytes and stimulate colonic fluid and electrolyte absorption. The impact of acute colitis on SCFA-stimulated Na+ absorption and SCFA absorption was examined. METHODS: Proximal colon from rabbits infected with Yersinia entercolitica, a pair-fed group, and controls was mounted in Ussing chambers, and Na+ transport, short-circuit current, and tissue conductance were examined during a basal period and after stimulation with the SCFAs, butyrate, or propionate. Propionate transport and luminal SCFA concentration were evaluated. RESULTS: Butyrate and propionate stimulated electroneutral Na+ absorption above basal levels in the control and pair-fed groups, as evidenced by significant increases in mucosal-to-serosal and net Na+ fluxes with no change in serosal-to-mucosal flux, short-circuit current, or conductance. Butyrate-stimulated Na+ absorption and propionate absorption were blocked by amiloride, an inhibitor of Na(+)-H+ exchange. In the infected group, both butyrate and propionate failed to stimulate colonic Na+ absorption above basal levels. Propionate absorption was inhibited, and epinephrine failed to stimulate Na+ or propionate absorption. Luminal SCFA concentrations were increased in acute colitis. CONCLUSIONS: Inhibition of SCFA-stimulated Na(+)-H+ exchange and SCFA absorption contribute to the diarrheal fluid loses observed in acute colitis and may reduce colonocyte energy supply.

Acute Disease↗
PubMed1975

'Sufficient' absorption--a quantitative method to replace 'exhaustive' absorption.

At present, the only guideline for removal of undesired reactivities from an antiserum is that no activity against the cross-reacting (undesired) antigens should remain after exhaustive absorption. Since this guideline sets no upper limit on the amount of undesired antigens required for an exhaustive absorption, waste of possibly precious material and of time in performing multiple sequential absorptions can result. To minimize the quantity of antigen and of experimental work required for an absorption, a quantitative approach is suggested: the antiserum is test-absorbed with various amounts of the undesired antigens, and antibody activity still present against these antigens is then tested. The results can be plotted as a curve by use of Reif's modification of the Von Krogh equation. Thus, the exact amount of undersired antigens sufficient to remove all detectable reactivity against these antigens can be determined. The procedure is termed 'sufficient' rather than 'exhaustive' absorption, to stress that only detectable amounts (rather than every last trace) of undesirable antibodies have been removed. The nomenclat re 'exhaustive absorption' gives no indication that any practical attempt to achieve it can hardly escape having the same limitations as 'sufficient absorption'; it is therefore suggested that the misleading non-quantitative nomenclature 'exhaustive absorption' be eliminated from immunological terminology. 'Sufficient absorption' has been applied to the absorption of undesired (blood group) antibodies from rabbit antisera to CEA.

ABO Blood-Group System↗
PubMed1985

Intestinal absorption of oestrone, oestrone glucuronide and oestrone sulphate in the rat in situ--I. Importance of hydrolytic enzymes on conjugate absorption.

The biliary excretion of steroid after administration of [3H]oestrone ([3H]E1), [3H]oestrone glucuronide ([3H]E1G) and [3H]oestrone sulphate ([3H]E1S) into the hepatic portal vein of anaesthetized rats was very rapid with more than 70% of E1S and greater than 80% of E1 and E1G excreted in the first 30 min. There was a lag period in the biliary excretion of E1S, this was less apparent with E1 and absent with E1G. Biliary excretion accurately reflects the amount of steroid in the portal circulation and was therefore used as an assessment of absorption from the gastrointestinal (GI) tract. Absorption (as judged by excretion in bile) was least after administration of each steroid into the stomach. The extent of absorption correlated well with the lipophilicity of the steroids as shown by their relative partition coefficients between n-octanol and pH 6.5 phosphate-buffered saline (E1 greater than or equal to E1S greater than or equal to E1G). There was no significant difference in excretion profile when the steroids were given into the caecum (at 5 h, E1, 46.3 +/- 9.1%; E1G, 42.2 +/- 14.5%; E1S, 39.9 +/- 7.1%). The similarity, despite marked differences in physicochemical properties, suggested conjugate hydrolysis to the parent steroid. In contrast, after administration into the small intestine, excretion of E1 was very rapid and was maximal at 1 h (72.5 +/- 8.0%); E1G showed a near-linear excretion rate (1 h, 14.4 +/- 3.0%; 5 h, 80.0 +/- 11.7%), whereas in comparison E1S excretion was low (1 h, 12.1 +/- 2.4%; 5 h, 36.9 +/- 2.7%). The involvement of hydrolytic enzymes in conjugate absorption was assessed. Ampicillin pretreatment (200 mg/kg/day for 2 days) reduced the absorption of E1G from both the proximal and distal small intestine (by approximately 50%) but had no effect on the absorption of E1S. There was, therefore, evidence that quantitative absorption of E1G requires prior hydrolysis (by mammalian and/or microbial enzymes) but intact absorption of E1S from this region of the tract was implicated. Ampicillin pretreatment reduced the absorption of both conjugates (greater with E1S) from the caecum; hydrolysis clearly precedes absorption from the caecum. The above findings were supported by an in vitro study which showed that ampicillin pretreatment abolished the hydrolysis of E1S by caecal contents but only partially reduced the hydrolysis of E1G. The presence of mammalian glucuronidase enzyme may account for this difference.

Ampicillin↗
PubMed2006

125I used for labelling of proteins in an absorption model changes the absorption rate of insulin aspart.

UNLABELLED: The aim of this study is to validate the ability of the disappearance model to predict absorption rates of insulin aspart in pigs. The disappearance model is used as a screening tool to estimate absorption rates after subcutaneous injections in humans or pigs especially of insulin and insulin analogues. The disappearance model measures remaining radioactivity at the injection site and therefore radioactive labelling of the insulin analogue is necessary. The labelling is done with 125I. One of the assumptions for the disappearance model to be reliable is that absorption rates of the labelled and non-labelled molecules are comparable. In this study, we compared disappearance data with absorption calculated from plasma samples of insulin aspart. The calculated absorption is based on non-labelled insulin aspart. The absorption rate from the disappearance data was statistical significant (p = 0.0028) different from the absorption rate based on plasma samples. A control study was carried out where 125I labelled insulin aspart was compared to 127I (the natural non-radioactive isotope) insulin aspart. In this study, absorption rate from the disappearance data and absorption rate based on plasma samples were similar (p = 0.63). CONCLUSION: Iodination of insulin aspart changes the subcutaneous absorption rate.

Absorption↗
PubMed2002

Initial uptake and absorption of nonheme iron and absorption of heme iron in humans are unaffected by the addition of calcium as cheese to a meal with high iron bioavailability.

BACKGROUND: Quantitative data on the mucosal uptake and serosal transfer of nonheme-iron absorption in humans and the effects of calcium on these components are limited. OBJECTIVE: Our objective was to measure the initial mucosal uptake and the subsequent serosal transfer of nonheme iron and to determine the effects of adding calcium to a meal on both heme- and nonheme-iron retention. DESIGN: Whole-gut lavage and whole-body scintillation counting methods were applied to determine the 8-h uptake of nonheme iron and the 2-wk retention (absorption) of heme and nonheme iron in healthy adults (n = 17) after the consumption of meals of radiolabeled food. RESULTS: The initial uptake and absorption of nonheme iron were 11% and 7%, respectively, and the absorption of heme iron was 15%. Two-thirds of the nonheme iron taken up by the mucosa within 8 h was retained by the body after 2 wk (serosal transfer index: 0.63). Serum ferritin correlated inversely with the initial uptake and absorption of nonheme iron, but not with the nonheme serosal transfer index or the absorption of heme iron. Adding calcium (127 mg in cheese) to the meal did not affect absorption. CONCLUSIONS: On the basis of its association with serum ferritin, the initial mucosal uptake was the primary control point for nonheme-iron absorption. An apparent reduction in heme-iron absorption associated with the lavage procedure suggested that uptake of heme iron may take longer and proceed further through the intestine than that of nonheme iron. The absorption of both forms of iron was unaffected by the addition of cheese to this meal with high iron bioavailability.

Administration, Oral↗
PubMed1975

Regional differences in oxalate absorption by rat intestine: evidence for excessive absorption by the colon in steatorrhoea.

Clinical studies suggest that steatorrhoea can be associated with excessive absorption of dietary oxalate. We examined the influence of bile salts, Ca++, and long-chain fatty acid on the absorption of oxalate and water by rat intestine in vivo. Absorption was measured under steady-state conditions during single-pass infusions. Each intestinal segment served as its own control. In jejunum, 10 mM taurocholate, the principal salt in rat bile, depressed absorption of oxalate and water. Absorption was not depressed further by Ca++ or linoleic acid. In ileum, 10 mM taurocholate did not inhibit absorption. Linoleic acid, 2 mM, depressed absorption of both oxalate and water. In colon 10 mM taurocholate decreased absorption. Net water transport was depressed further when linoleic acid was added to the infusion, but oxalate absorption was enhanced. Ca++ negated these effects of linoleic acid. It is concluded that long-chain fatty acids may enhance the absorption of oxalate from the rat colon. This observation may be relevant to understanding hyperoxaluria in patients with steatorrhoea.

Animals↗
PubMedDate not supplied

3-0 methylglucose absorption in vivo correlates with nutrient absorption and intestinal surface area in experimental short bowel syndrome.

BACKGROUND: Inert carbohydrate probes are widely used to study intestinal permeability and examine the passive uptake of markers. This study examined the use of quantifying 3-0 methylglucose (3-0 MG) absorption as a marker of intestinal surface area and active nutrient transport capability. METHODS: Using a rat model, varying degrees of short bowel syndrome (SBS) were induced: sham operation (intestinal transection only), 50% resection (R50), 75% resection (R75), and 90% resection (R90; n = 6 to 8 in each group). Animals were pair fed, and over days 5 and 6 postoperation, a balance study was done to quantify absorption of dietary fat, protein, and carbohydrate. On day 7, animals were gavaged with the test solution containing 3-0 MG, lactulose, and mannitol, followed by a 16-hour urine collection. Urine recovery of probes was quantified using high-performance liquid chromotography. Animals were then killed, and the gross and microscopic intestinal morphology was determined. RESULTS: As expected, increased resection resulted in reduced absorption of dietary nutrients and 3-0 MG, which reached significance in the R90 resected animals. 3-0 MG absorption was significantly correlated with intestinal surface area and the absorption of dietary protein and fat (p < .01 for all comparisons). Interestingly, 3-0 MG absorption was not significantly correlated with the absorption of dietary carbohydrate. CONCLUSIONS: 3-0 MG absorption is a useful marker of functional intestinal surface area and of the absorption of dietary fat and protein in experimental SBS. 3-0 MG may be a useful marker of nutrient absorptive capacity in patients with SBS; further study is indicated.

3-O-Methylglucose↗
PubMed2004

Studies on the intestinal absorption of low molecular weight heparin using saturated fatty acids and their derivatives as an absorption enhancer in rats.

Intestinal absorption of low molecular weight heparin (LMWH) as well as unfractionated heparin (UFH) is limited due to its large molecular size and extensive negative charge. Development of its oral formulations would allow outpatient treatment with LMWH and UFH, and contribute a reduction in hospital expenses. The present study was aimed at evaluating the absorption enhancers Labrasol and Gelucire 44/14, which mainly consist of glycerides and fatty acids esters, to improve the intestinal absorption of LMWH. The absorption effects of saturated fatty acids with several carbon chain lengths (C6-C14) were also investigated. LMWH formulated with or without absorption enhancer was administered to the duodenum of fasted rats. The doses of LMWH and absorption enhancer were 20 mg/kg and 30 mg/kg, respectively. Plasma anti-Xa activity was measured as a marker of the LMWH absorption. By administration of the LMWH formulation with Labrasol but not with Gelucire 44/14, the plasma anti-Xa activity was increased to a level above 0.2 IU/ml which is the critical level for elucidation of its anticoagulant activity. Saturated fatty acids also enhanced the intestinal absorption of LMWH, and the order of absorption-enhancing effect was C10=C12>C14>C16>C8> or =C6. These results suggest that the intestinal absorption of LMWH varies with carbon chain lengths of the saturated fatty acids.

Adjuvants, Pharmaceutic↗
PubMed1998

Absorption enhancers as tools to determine the route of nasal absorption of peptides.

The nasal absorption of a series of peptides was studied in order to examine the relationship between extent of absorption and lipophilicity and absorption enhancers were used to probe the mechanism of peptide absorption. An in situ rat nasal perfusion technique was employed to assess the nasal absorption of a series of peptides, D-FGGGGG (D-FG5), D-FD-FGGGG (D-F2G4) and D-FD-FD-FGGG (D-F3G3), [D-ala2, D-leu5]enkephalin (YD-AGFD-L) and thyrotrophin releasing hormone (TRH). The enhancers sodium tauro-24,25 dihydrofusidate (STDHF), ethylene diamine tetraacetic acid (EDTA and dimethyl-beta-cyclodextrin (DMbetaCD) were utilized to improve and elucidate the mechanisms of peptide absorption. There was no significant relationship between extent of peptide absorption and lipophilicity as determined by C log P values. STDHF was a potent absorption enhancer but demonstrated overt toxicity. Conversely, EDTA did not demonstrate extensive toxicity but was found to be a poor absorption enhancer. DMbetaCD displayed some toxicity and was also found to inhibit the absorption of D-FG5,D-F2G4 and D-F3G3. This reduction is likely to be a result of the peptide/DMbetaCD complex formation. The peptides studied appear to be predominantly absorbed by a passive paracellular mechanism.

Absorption↗
PubMed2002

Concentration-dependent preferences of absorptive and excretive transport cause atypical intestinal absorption of cyclic phenylalanylserine: small intestine acts as an interface between the body and ingested compounds.

Intestinal absorption of cyclic phenylalanylserine (cyclo(Phe-Ser)), a precursor of gliotoxin, was studied in isolated rat small intestine as a model cyclic dipeptide. Absorption clearance (CLabs) decreased in the presence of glycylsarcosine, cephalexin or cephradine, substrates for H+/oligopeptide cotransporter (PEPT1). CLabs of cyclo(Phe-Ser) also decreased at 4 degrees C. These indicate that cyclo(Phe-Ser) is in part transported by PEPT1. However, Eadie-Hofstee plot of absorption revealed an atypical profile at lower concentrations of cyclo(Phe-Ser) (around 0.1 mM). Moreover, comparative experiments of absorptive and excretive transport showed that excretive transport from the serosal to mucosal side of isolated intestinal tissue at a 0.1 mM cyclo(Phe-Ser) was superior to absorptive transport from the mucosal side to the serosal side, and vise versa at a 1 mM cyclo(Phe-Ser). These results as well as the results of kinetic analysis indicate that intestinal absorption consists of passive transport, carrier-mediated absorptive transport by PEPT1 and carrier-mediated excretive transport, resulting in atypical absorption. Although cyclic dipeptides have potentials for drug, their intestinal absorption may be complex. The results of this study lead us conclude that absorptive and excretive transport by the small intestine acts as an interface between the body and ingested compounds.

Algorithms↗
PubMed1991

Enhanced rectal and nasal absorption of human epidermal growth factor by combined use of the absorption promoter and the synthetic polymer in rats.

Previously, the presence of sodium carboxymethylcellulose (CMC Na) in addition to an absorption promoter, sodium caprate (C10 Na), in the dosing solution was found to be necessary for the enhancement of the rectal absorption of human epidermal growth factor (hEGF). In the present study, other synthetic polymers and absorption promoters were examined for their ability to enhance the rectal and nasal absorption of hEGF in rats. The effect of polymers in combined use with 100 mM C10 Na on the rectal absorption of hEGF was in the following order: 1% methylcellulose 1% hydroxypropylmethylcellulose 0.1% polyacrylic acid 1% CMC Na. Other absorption promoters such as N-lauroyl-alanine (C12-A) and dihydroxy-bile salts also enhanced the rectal absorption of hEGF in combined use with CMC Na. In order to confirm the increased rectal absorption of hEGF, the disappearance of hEGF from the rectal loop was examined. When hEGF in a 1% CMC Na solution (200 ug/kg) was administered in the rectal loop, the disappearance percent of hEGF during 60 min was 13.9% of the dose, although hEGF was not detected in the plasma. The presence of promoters such as 10 mM C10 Na or 15 mM C12-A in 1% CMC Na increased the disappearance percent to about 50% in a dosing range of hEGF from 100 to 500 ug/kg. On the other hand, a markedly enhanced nasal absorption of hEGF by 100 mM C10 Na was observed even in the absence of any polymer in a dising solution. However, addition of CMC Na into the dosing solution accelerated the rate of nasal absorption of hEGF in early phase.(ABSTRACT TRUNCATED AT 250 WORDS)

Acrylic Resins↗
PubMedDate not supplied

Absorption of iothalamate after oral administration and absorption enhancement by amino acids in dogs and rats.

The oral absorption of iothalamate and the effect of amino acids on its absorption were studied in 6 dogs and 6 rats using a simple HPLC assay. The results showed that iothalamate was absorbed in dogs, averaging 9.9, 8.5, and 10.0 per cent following the administration of 40 and 100 mg kg-1 of iothalamic acid capsules and 50 mg kg-1 of sodium iothalamate solution, respectively. The absorption from the capsule was slower and more sustained than that from the solution. In rats, the absorption appeared to be dose-independent (averaging about 4.2 per cent) in the dose range of 20-800 mg kg-1. The low bioavailability obtained was mainly due to the high polarity of iothalamate molecules as suggested by the GI recovery and in vitro partition studies. Among several amino acids tested as possible ion-pair formers, only homoarginine hydrochloride increased the partition of iothalamate into chloroform layer. However, both homoarginine hydrochloride and arginine hydrochloride at the amino acid/iothalamate molar ratio of 25 were found to significantly enhance (about 70 per cent) the iothalamate absorption in dogs. The in situ rat small intestinal loop study indicated that the absorption-enhancing effect of arginine was sodium dependent. At the sodium chloride concentration of 0.09 M, no significant increase in the absorption was observed, while at the concentration of 0.3 M or higher, a marked increase (about twofold) was obtained in both upper and lower intestine. Thus, the mechanism of the amino acids in facilitating the iothalamate absorption may be more closely related to the active amino acid transport system rather than the possible increase in lipophilicity of the ion-pair formed. The potential use of such naturally occurring, relatively non-toxic amino acids for increasing the GI absorption of water-soluble weak acids or bases through ion-pair formation remains to be fully investigated.

Administration, Oral↗
PubMed1977

GI drug absorption in rats exposed to cobalt-60 gamma-radiation II: in vivo rate of absorption.

The rate of absorption of sulfanilamide, bretylium tosylate, sulfisoxazole acetyl, and riboflavin was studied in rats exposed to 850 rad of cobalt-60 gamma-radiation either 1 or 5 days before oral drug administration. Polyethylene glycol 4000 was administered with sulfanilamide; its distribution along the GI tract indicated that the gastric emptying rate was reduced threefold at 1 day postirradiation but returned to normal at 5 days postirradiation; the small intestinal transit rate was not detectably altered by irradiation. At 1 day postirradiation, there was a marked decrease in the absorption rate of sulfanilamide, a smaller, although significant, decrease in the absorption rate of sulfisoxazole acetyl and bretylium, and an increase in the absorption rate of riboflavin. At 5 days postirradiation, the drug absorption rate was normal. The changes in the absorption rate of the drugs were due to a radiation-induced reduction in the gastric emptying rate; the permeability of the GI epithelium did not appear to be affected by radiation. The results indicate that, immediately following irradiation, a marked reduction in the gastric emptying rate causes a pronounced reduction in the absorption rate of rapidly absorbed drugs, a less pronounced reduction in the absorption rate of drugs that are absorbed slowly because of slow dissolution or slow diffusion across the GI epithelium, and an increase in the absorption rate of drugs that are absorbed by a saturable mechanism provided the mechanism is not impaired by irradiation.

Animals↗
PubMed1985

Mechanism of nasal absorption of drugs I: Physicochemical parameters influencing the rate of in situ nasal absorption of drugs in rats.

The effect of rate of perfusion, volume, pH of the perfusate, and partition coefficient of the drug on the rate of in situ nasal absorption in rats was examined. The studies showed that the rate constant for the nasal absorption of phenobarbital was independent of the rate of perfusion above a value of 2 mL/min. The nasal absorption of benzoic acid was found to depend on the pH of the perfusate with the benzoate anion being absorbed at a rate one-fourth of that of benzoic acid. The effect of lipid solubility on the extent of nasal absorption was studied using a series of barbiturates. The rate and extent of absorption was found to be dependent on the chloroform-water partition coefficient of the barbiturate. The effect of the volume of the perfusate on the absorption rate constant of phenobarbital, phenol red, tyrosine, and propranolol was studied. The data obtained showed that a linear relationship existed between the rate constants of absorption and the reciprocal of the volume of the perfusate. Using this in situ relationship it was possible to predict in vivo absorption rate constants for propranolol and L-tyrosine when volumes of 0.1 mL were administered. The calculated values for these compounds were found to be close to those determined in in vivo experiments. This indicates that the in situ technique can be used to predict in vivo absorption rate constants.

Absorption↗
PubMed1993

Elucidation of the role of hydrophobic bonding in influencing intestinal absorption of model sulfonamides and revealing possible mechanism of drug absorption in rat model.

A recirculation technique was used to study the first-order kinetics of intestinal absorption of un-ionized sulfadiazine, sulfamerazine, and sulfamethazine in rats in situ at 32, 35, and 38 degrees C. The absorption rate constant (Kab) of each sulfonamide increased with increase in temperature and, at each temperature, Kab was the highest for sulfamethazine and the lowest for sulfadiazine. Applying the activated complex formation theory, the energy of activation (Ea), free energy of activation (delta F*), enthalpy of activation (delta H*), and entropy of activation (delta S*) of absorption were determined for the sulfonamides to gain some insight into the mechanism of their intestinal absorption. The high values of delta F* indicated that the barrier for sulfonamide absorption was great. For each drug, the value of delta H* was positive and that the delta S* negative. However, delta H* and delta S* were the highest for sulfamethazine and the lowest for sulfadiazine, thus revealing the influence of hydrophobic bonding in increasing Kab of the sulfonamides with the increase in methyl group content of their molecules. By considering the facts that (1) the microvillus membrane of the intestinal absorptive cells regulates the rate of passive absorption of drugs, (2) the microvillus membrane is rich in proteins, which are located external to the membrane and exposed to the intestinal fluid, and (3) hydrophobic bonding contributes to the activation parameters of absorption, it was postulated that the activated complex formed in the absorption process consisted of a transient association of the sulfonamide molecules with some protein component of the microvillus membrane.

Animals↗
PubMed1978

Arachidonic acid intestinal absorption: mechanism of transport and influence of luminal factors of absorption in vitro.

The mechanism and characteristics of intestinal absorption of arachidonic acid were studied in vitro using everted intestinal sacs of the rat. Arachidonic acid absorption was studied at concentrations of 5 micron to 8.36 mM. The plot of absorption rate vs. concentration fitted best to a rectangular hyperbola at low micron concentrations and to a straight linear relationship in the mM range of concentrations. Metabolic inhibitors and uncouplers did not change absorption in either range of concentrations. The absorption of arachidonic acid increased with thinning of the unstirred water-layer, decrease in the pH, or the substitution of sodium taurocholate by Pluronic F 68 OR Tween 80. Absorption decreased following the equimolar additions of oleic, linoleic, and linolenic acids. Absorption rate did not change when the taurocholate concentration was varied from 5-15 mM or following the additions of butyric or glutamic acids, leucine, lysine, or dextrose. It was concluded that arachidonic acid is absorbed by a concentration-dependent dual mechanism of transport which is not energy dependent. At the low micron range of concentrations, facilitated diffusion is predominant, while at mM concentrations, simple diffusion is the dominant mechanism of absorption. Changes in the intestinal fluid composition, flow rate, and pH can modify the rate of absorption of arachidonic acid.

Animals↗
PubMed1998

A comparison of lycopene and canthaxanthin absorption: using the rat to study the absorption of non-provitamin A carotenoids.

The purpose of this study was to validate the use of the mesenteric lymph duct cannulated rat to study the absorption of carotenoids which do not have provitamin A activity. The absorption of two carotenoids, a hydrocarbon carotenoid (lycopene) and a xanthophyll carotenoid (canthaxanthin), were investigated. In the first experiment, lipid emulsions containing lycopene (LYC) or canthaxanthin (CTX) were continuously infused into the duodenum, and lymph was collected for analysis at 2-h intervals. The time course for absorption of carotenoids and triacylglycerol (TAG) was similar. Carotenoids and TAG reached steady-state concentrations in the lymph by 6 h. There was no evidence for a delayed release of either carotenoid from the intestine relative to TAG. During a second experiment, emulsions containing increasing concentrations of LYC or CTX (5, 10, 15, 20 mumol/L) were infused. The LYC and CTX in the lymph increased in a dose-dependent manner. The average efficiency of CTX absorption was 16% while the efficiency of LYC absorption averaged only 6%. Efficiency of carotenoid absorption was not related to concentration infused. Finally, to test whether LYC and CTX interact during absorption both were added to a lipid emulsion at equal concentrations (20 mumol/L) and infused. The carotenoids did not significantly affect each other's absorption. These results demonstrate the usefulness of the rat as an animal model to study the absorption of non-provitamin A carotenoids.

Animals↗