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At least 325 records · Page 18Linked to original sources
PubMed1980

[Effects of perfusion flow rates on the intestinal absorption of carbohydrates].

The effects of five perfusion flow rates (4,5, 9, 12, 30 and 60 ml/h) on the intestinal absorption of glucose, fructose and sucrose were studied in the rat with a "temporary" Thiry-Vella loop (jejunum = 20 cm). Sucrose hydrolysis and intestinal transport of actively and passively absorbed solutes were markedly affected when the flow rates rose to a value higher than the limiting rate of 12 ml/h. With a flow rate up to 60 ml/h, glucose and fructose were absorbed at the same rate, but this was not due to thinning of the unstirred water layer. Sucrose hydrolysis was likewise completely inhibited. This result cannot be attributed to a product inhibition because of the absence of hexoses in the exit perfusate. These observations had important implications in the comparison of the intestinal absorption of many nutrients to evaluate the optimal perfusion rate corresponding to intestinal function integrity.

Animals↗
PubMed2000

Intestinal transport and metabolism of glucose-conjugated kyotorphin and cyclic kyotorphin: metabolic degradation is crucial to intestinal absorption of peptide drugs.

Intestinal transport and metabolism of modified kyotorphin (KTP) were studied in rats. Modified KTPs studied were C-terminally modified KTP with p-aminophenyl-beta-D-glucoside (KTP-pAPbeta glc), N-terminally modified KTP-pAPbeta glc with t-butyloxycarbonyl group (Boc-KTP-pAPbeta glc) and the N- and C-terminally modified KTP by cyclization (cyclic KTP). KTP-pAPbeta glc was metabolized at a similar rate to that of KTP, and did not appear on the serosal side. Although Boc-KTP-pAPbeta glc was also metabolized, it was more stable than KTP and appeared on the serosal side. Cyclic KTP was also quite stable and appeared on the serosal side. The modified KTPs were evaluated kinetically for absorption consisting of membrane transport and metabolism. Absorption clearance (CL(abs)) of cyclic KTP, Boc-KTP-pAPbeta glc and Boc-KTP was higher than that of KTP (0.247 microl/min/cm) (Mizuma et al., Biochim. Biophys. Acta 1335 (1997) 111-119), which is the theoretical maximum by complete inhibition of peptidase activity, indicating that derivatization of KTP increases the membrane permeability. Furthermore, the data clearly showed that the greater the metabolic clearance (CL(met)) of KTP and the KTP derivatives, the lower the absorption clearance (CL(abs)). These results and further simulation study led to the conclusion that metabolic degradation in the intestinal tissues is more critical than membrane permeability (transport) for oral delivery of peptide drugs. Based on the stability of cyclic KTP in serum, this appears to be a good candidate analgesic peptide drug.

Acetaminophen↗
PubMed1984

Morphine-neural interactions on canine intestinal absorption and blood flow.

Intestinal Na and H2O fluxes and blood flow were determined in extrinsically denervated or innervated ileum of fed dogs during intra-arterial (0.2, 2, 20 micrograms min-1) or intraluminal (4, 40, 400 micrograms ml-1) morphine sulphate infusion. 3H2O and 22Na were used to determine unidirectional fluxes and 3H2O clearances were used to determine total segmental and absorptive site blood flow. Net Na and H2O absorption decreased with time in innervated gut segments but were unchanged in denervated segments. Intra-arterial morphine prevented the decrease in net Na and H2O absorption in innervated segments due to increases in unidirectional absorptive fluxes. Intra-arterial morphine did not affect absorption in denervated segments. Intraluminal morphine increased net Na and H2O absorption from both innervated and denervated ileal segments due to increases in the unidirectional absorptive fluxes. Absorptive site blood flow was linearly related to unidirectional absorptive Na fluxes in each group although not with the same slopes. The increment in absorptive site blood flow vs. absorptive Na flux was greatest with luminal morphine, intermediate with intra-arterial morphine and in denervated segments without morphine and least in innervated segments. It was concluded that intra-arterial morphine inhibits an antiabsorptive effect of extrinsic nerves and that intraluminal morphine promotes an absorptive effect which could be direct or mediated through intrinsic nerves.

Animals↗
PubMed1975

Intestinal absorption of free and protein-bound dietary methionine in the rat.

Intestinal absorption of radioactive free and protein-bound dietary methionine (Met) and changes in plasma amino acids were observed after feeding Met-supplemented test meals. Plasma and gastrointestinal contents were collected from 15 minutes to 16 hours after feeding. Plasma amino acids were determined after ad libitum ingestion of diets containing free Met. Protein-bound Met in fresh egg white and free Met left the stomach at the same rate, but protein-bound Met in dried egg white and free Met were emptied from the stomach at different rates. Free Met was absorbed from the intestine more rapidly than protein-bound Met. Concentrations and molar ratios of various free amino acids in plasma changed briefly in response to Met-supplemented single test meals. Long-term changes were observed when Met-supplemented diets were fed ad libitum. Prolonged ingestion of supplemented diets may cause sustained alterations in the plasma amino acid pattern.

Amino Acids↗
PubMed1993

Intestinal absorption and malnutrition in patients with the acquired immunodeficiency syndrome (AIDS).

The relation of small intestinal dysfunction and malnutrition (body composition and serum index parameters of nutrition) was investigated in 36 male patients with AIDS. Mucosal absorptive capacity was assessed by the 25 g D-xylose test. D-xylose absorption (2 h - serum profile and 5 h - urine) classified 17 patients as having impaired and 19 patients as having normal absorption. In both groups body weight, body mass index as well as body composition analysis indicated malnutrition when compared to healthy male controls (n = 340) or asymptomatic HIV-infected patients (n = 26). Patients with abnormal D-xylose test had more severe malnutrition indicated by a lower body cell mass (17.7 +/- 5.4 vs. 22.5 +/- 4.5 kg; p < 0.01) and an increased ratio of extracellular mass to body cell mass (1.99 +/- 0.82 vs. 1.45 +/- 0.46 p < 0.01). Total serum protein, albumin, cholinesterase activity, cholesterol and LDL were significantly diminished in AIDS-patients with abnormal D-xylose test compared to those with normal D-xylose absorption. Intestinal dysfunction indicated by decreased D-xylose Intestinal dysfunction indicated by decreased D-xylose absorption thus represents an important feature of malnutrition and wasting, and patients with abnormal D-xylose absorption have more profound impairment of body composition, visceral proteins and lipids reflecting malnutrition than patients with unaffected intestinal absorption.

AIDS-Related Opportunistic Infections↗
PubMed1990

Intestinal absorption of vitamin E in experimental renal failure.

We studied intestinal absorption of vitamin E in rats with experimental renal failure (RF) and in sham-operated normal and pair-fed controls using in vivo perfusion and in vitro everted sacs. The in vivo absorption rates per unit of intestine length were significantly reduced in RF and pair-fed groups. Expression of data per unit of intestine weight gave normal values in the pair-fed but depressed values in the RF animals. Vitamin E uptake in vitro was significantly increased in RF animals, suggesting enhanced permeability. We conclude: (i) vitamin E absorption in vivo is impaired in experimental RF; (ii) this is in part due to reduced nutrient intake; and (iii) disparity between in vivo and in vitro results suggests the presence of some inhibitory influence(s) in intact animals with RF.

Acute Kidney Injury↗
PubMed1979

Interaction of cations and chelators with the intestinal absorption of tetracycline.

The influence of certain compounds on intestinal absorption of tetracycline was tested, using two different in vivo techniques: a) Disappearence of the drug from perfused intestinal segments of the rabbit; b) Measuring urinary excretion in the rat after oral dosage. Ca2+ and Fe2+ ions both reduced the permeation rate of tetracycline by about 30%. In presence of Ca2+ and salicylate ions, leading to ion-pair formation with the antibiotic, intestinal uptake was significantly increased in comparison to experiments where only calcium was present. A more pronounced increase was observed with EDTA. Phosphate ions had different effects on the uptake of the antibiotic in both experimental techniques. Possible mechanisms are discussed.

Animals↗
PubMed1994

Relationship between the suppressive actions on intestinal absorption and on cGMP production for the natriuretic peptide family in dogs.

1. The aim of this study was to investigate whether the suppressive effects of atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP) and C-type natriuretic peptide (CNP) on net intestinal absorption were related to guanosine 3',5'-cyclic monophosphate (cGMP) production in the intestine. 2. We measured the plasma cGMP concentration of the arterial, jejunal and ileal venous blood after intravenous infusions of natriuretic peptides (97 pmol/kg per min for 30 min) in anaesthetized dogs. 3. The infusion of ANP increased cGMP concentration of the aortic blood by 49.9 +/- 9.0 (pmol/mL), BNP by 71.8 +/- 12.3 and CNP by 5.5 +/- 1.3. The increases in cGMP after ANP and BNP were larger than after CNP. The infusion of ANP increased jejunal arteriovenous differences in cGMP concentration by 69.9 +/- 3.5 (pmol/mL) and ileal arteriovenous differences by 8.7 +/- 3.2. In BNP infusion, the jejunal and ileal arteriovenous differences in cGMP concentration tended to increase by 15.6 +/- 5.8 (pmol/mL) and by 14.8 +/- 6.6 but neither were significant. CNP infusion did not change the jejunal and ileal arteriovenous differences in cGMP concentration. 4. These results suggest that, while the actions of ANP on intestinal absorption may be mediated by cGMP, those of BNP and CNP are not.

Animals↗
PubMed1979

[Evaluation of intestinal absorption of calcium by means of double-isotope methods and oral administration of the tracer].

The percent intestinal absorption of calcium was measured in normal volunteers and in patients with idiopathic hypercalciuria employing the deconvolution method, the ratio of the two administered isotopes at equilibrium and the percent of dose present in plasma 2 hr after oral administration of the tracer. Comparison of results obtained showed that the technique based on the ratio between the two radioisotopes overestimates intestinal absorption by about 9% with respect to values calculated with the deconvolution method, but gives results comparable to those determined by oral administration of the isotope. The percent dose of the tracer 2 h after i.v. administration is closely correlated with the size of the miscible calcium pool. A less significant correlation exists between the size of the pool and percent of the dose 2 h after oral administration.

Administration, Oral↗
PubMed1999

Theoretical calculation and prediction of intestinal absorption of drugs in humans using MolSurf parametrization and PLS statistics.

A method for modeling and prediction of the intestinal absorption of drugs in humans using theoretically computed molecular descriptors and multivariate statistics has been investigated using 20 diverse drug-like compounds. The program MolSurf was used to compute theoretical molecular descriptors related to physicochemical properties such as lipophilicity, polarity, polarizability and hydrogen bonding. The multivariate Partial Least Squares Projections to Latent Structures (PLS) method was used to delineate the relationship between the intestinal absorption of drugs in humans and the theoretically computed molecular descriptors.Good statistical models were derived. Properties associated with hydrogen bonding had the largest impact on absorption and should be kept to a minimum to promote high absorption. High charge-transfer properties and the presence of surface electrons, i.e. valence electrons, which are not tightly bonded to the molecule, were also found to promote high absorption.

Computer Simulation↗
PubMed2000

The rhamnogalacturonan-II dimer decreases intestinal absorption and tissue accumulation of lead in rats.

The rhamnogalacturonan-II dimer (dRG-II) forms strong complexes in vitro with lead (Pb) and other selected cations. We examined the in vivo bioavailability of Pb complexed with dRG-II and the effect of unleaded dRG-II on the intestinal absorption and tissue retention of Pb in rats. Forty male Wistar rats were divided into four groups. Each group consumed a purified control diet for 3 wk or the same diet supplemented with: i) 3 mg of Pb/kg, ii) 0.5 g of leaded dRG-II/kg, or iii) 0.5 g of leaded dRG-II/kg and 4.5 g of unleaded dRG-II/kg. The leaded dRG-II provided approximately 3 mg of Pb/kg of diet. A chemical balance study was conducted during the last 5 d of the 3-wk study, and blood and organs were sampled for Pb and mineral analyses. The apparent intestinal absorptions of Pb were 62.3, 15.2, 11.8 and -0.1%, and Pb balances were 1.9, 9.6, 5.6 and -0.2 microg/d for the control and the three experimental groups, respectively. The Pb complexed with dRG-II was less available than Pb acetate, as reflected by significantly lower blood and tissue Pb levels. The addition of unleaded dRG-II decreased the intestinal absorption and the tissue retention of Pb significantly. We further found that the apparent absorption and status of magnesium, zinc and iron were unaffected by Pb treatment or dRG-II addition. We conclude that dRG-II may be useful in decreasing toxicity related to chronic Pb exposure. Human studies will be necessary however, to further evaluate the clinical utility of this beneficial effect.

Analysis of Variance↗
PubMed1990

Immunolocalization of transferrin and transferrin receptor in mouse small intestinal absorptive cells.

The mechanisms by which the duodenal mucosa absorbs iron are unknown. Insorption into absorptive cells of luminal iron bound to transferrin via receptor-mediated endocytosis has been hypothesized, but transferrin and transferrin receptor are absent in apical microvillous brush borders of small bowel biopsies taken from fasted patients and normal volunteers. We hypothesized that a normal iron-containing diet might induce the transient appearance of transferrin and transferrin receptor in apical brush borders of small intestinal absorptive cells in a normal mouse that was provided iron-containing chow until the moment of sacrifice. Light and electron microscopic immunolocalization of transferrin and transferrin receptor in proximal small intestinal absorptive cells was limited to basolateral membranes and coated pits of cells predominantly in the crypts and basal regions of the villi. Transferrin and transferrin receptor were not detected in apical microvillous brush border membranes of these enterocytes. In parallel immunolocalization protocols designed to show the ability to immunodetect other antigens at these locations, maltase and proteoglycan were demonstrated in apical microvillous brush border membranes and in basolateral membranes, respectively, in absorptive cells of small intestinal villous tip, base, and crypt regions. Furthermore, transferrin and transferrin receptor were immunolocalized in hepatocyte sinusoidal microvillus membranes. We conclude that food does not induce the appearance of immunodetectable transferrin and transferrin receptor in the apical microvilli of small intestinal absorptive cells and, therefore, that these iron transport proteins are not involved in the apical microvillous membrane transport of luminal dietary iron.

Animals↗