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PubMed1990

[Intestinal absorption of vitamin E in children with atrophy of the jejunal mucosa].

The intestinal absorption of vitamin E is often thought to be closely correlated to that of fatty acids, but the biochemical mechanisms involved in the process are still not clear. For this reason, the present study aimed to assess the absorption of triglycerides and vitamin E, following oral administration, in 11 children with suspected malabsorption syndromes. Intestinal biopsy in 9 children showed the presence of a flat mucosa, whereas no changes were present in 2 patients. The results confirm the inverse correlation between the absorption of triglycerides and vitamin E, as if tocopherols used an independent system of transport. These findings contrast with those reported in the literature perhaps due to the low level of precision of colorimetric techniques previously used to assay vitamin E.

Atrophy↗
PubMed1995

Magnetic resonance imaging of the hepatobiliary system: intestinal absorption studies of manganese mesoporphyrin.

RATIONALE AND OBJECTIVES: We studied the intestinal absorption of manganese mesoporphyrin (Mn-mesoporphyrin), a potential oral hepatobiliary contrast agent. METHODS: Mn-mesoporphyrin was complexed with monoolein and taurocholate (mixed micelles). Portal venous delivery and biliary excretion were measured after intestinal administration in rats and rabbits, and the mechanism of intestinal transport was studied in a combined lymph-bile fistula model in rats. T1-weighted magnetic resonance (MR) images of the liver were obtained in rats and domestic pigs before and after gastric administration of Mn-mesoporphyrin in mixed micelles. RESULTS: A 2.2-fold increase of portal venous Mn concentration was found 90 min after intestinal administration of the complex. None was found in the lymph collected from the thoracic duct, indicating a transcellular transport mechanism through the intestinal mucosa with portal venous delivery. Mn-mesoporphyrin levels in bile peaked between 240 and 270 min after administration (200-fold increase). The greatest liver enhancement (20-90%) was measured 360 min after administration. CONCLUSION: The feasibility of intestinal delivery of Mn-mesoporphyrin, a lipophilic hepatobiliary contrast agent was demonstrated.

Animals↗
PubMed1995

Intestinal absorption of dideoxynucleosides: characterization using a multiloop in situ technique.

The intestinal absorption of dideoxynucleosides was studied in rabbits, using a closed-loop mesenteric-sampling in situ technique developed in this laboratory, and the kinetic profiles were characterized. Each of the dideoxynucleosides exhibited different dependence on the intestinal regions studied: 3'-azido-2',3'-dideoxythymidine was best absorbed from the ileum, while 2',3'-dideoxyinosine and 2',3'-dideoxycytidine were preferentially absorbed from the jejunum. The results were validated by the mass-balance approach; the percent of drug retained in the intestinal lumen and that degraded at the intestinal pH, by colonic flora, in the intestinal tissue, and in plasma were assessed.

Animals↗
PubMed1999

Intestinal absorption of vitamins.

This article provides an overview of advances in understanding the cellular and molecular mechanisms and regulation of intestinal absorption processes of vitamins. The vitamins covered are the water-soluble vitamins folic acid, cobalamin (vitamin B12), biotin, pantothenic acid, and thiamine (vitamin B1) and the lipid-soluble vitamin A. For folate, significant advances have been made in regard to i) digestion of dietary folate polyglutamates to folate monoglutamates by the cloning of the responsible enzyme; ii) identification of the cDNA responsible for the intestinal folate transporter; iii) delineation of intracellular mechanisms that regulate small intestinal folate uptake; and iv) identification and characterization of a specific, pH-dependent, carrier-mediated system for folate uptake at the luminal (apical) membrane of human colonocytes. Studies on cobalamine have focused on cellular and molecular characterization of the intrinsic factor and its receptor. Studies on biotin transport in the small intestine have shown that the uptake process is shared by another water-soluble vitamin, pantothenic acid. Furthermore, a Na-dependent, carrier-mediated biotin uptake system that is also shared with pantothenic acid has been identified at the apical membrane of human colonocytes. This carrier is believed to be responsible for the absorption of the bacterially synthesized biotin and pantothenic acid in the large intestine. Also, preliminary studies have reported the cloning of a biotin transporter from the small intestine. As for thiamine intestinal transport, a study has shown thiamine uptake by small intestinal biopsy specimens to be via a carrier-mediated, Na-independent mechanism, which appears to be up-regulated in thiamine deficiency. Studies on vitamin A intestinal absorption have shown the existence of a receptor-mediated mechanism for the uptake of retinol bound to retinol-binding protein in the small intestine of suckling rats. Another study has shown that retinoic acid increases the mRNA level of the cellular retinol binding protein II and the rate of retinol uptake by Caco-2 intestinal epithelial cells. The study suggested that retinoids may play a role in the regulation of vitamin A intestinal absorption.

Journal Article↗
PubMed1988

Growth rate, muscle protein composition, intestinal absorption of D-galactose and L-leucine and nitrogen balance in rats fed the raw legume Chamaecytisus proliferus L.

Growth rate, nitrogen balance, skeletal muscle nitrogen fractions and in vivo intestinal absorption of D-galactose (2 mM) and L-leucine (20 mM) have been measured in male growing rats (90-100 g initial body weight) fed 12% protein diets containing either casein (control) or the raw leafy legume Chamaecytisus proliferus L. (Western Canary Islands). As compared to control casein-fed rats, those fed the raw legume diet exhibited a significant reduction (P less than 0.01) in the rate of growth, nitrogen balance parameters, sarcoplasmic nitrogenous fraction of skeletal musculature and in vivo intestinal absorption of galactose and leucine; however, the non-protein nitrogenous fraction has been found significantly higher (P less than 0.01) than that of control animals, whereas the myofibrillar nitrogenous fraction remained unchanged. The possible nature of these findings is discussed.

Animals↗
PubMedDate not supplied

[Characteristics of disease and involution-induced changes in intestinal absorption].

With advancing age functional and morphological changes take place within the intestinal tract. The absorption rate (constant k12), the time of appearance of the relative maximum of the D-xylose concentrations in the blood serum after oral administration (time tm), and especially the extent of the relative absorption in the small intestine until the time tm RR (tm) determined by graphic-mathematical evaluation of the blood levels kinetics of D-xylose after oral and intravenous administration, are useful parameters for differentiation between involutively and pathological changes in intestinal absorption. Absorption disorders in old age are due to morbidity and not, sui generis, to involution.

Adolescent↗
PubMed1993

Fish oil modifies effect of high cholesterol diet on intestinal absorption in diabetic rats.

Omega-3 fatty acids ('fish oil') reduce the intestinal absorption of glucose and lipids in normal and in diabetic rats, but their effect is altered by the presence of saturated or poly-unsaturated omega-6 fatty acids in the diet. This study was undertaken to test the hypothesis that the influence of fish oil on the intestinal uptake of nutrients in diabetic rats is also influenced by the cholesterol content of the diet. Streptozotocin diabetic rats were raised for 2 wk on semisynthetic diets in which the lipid composition was derived mainly from beef tallow (BT), beef tallow plus cholesterol (BTC), fish oil (FO), or fish oil plus cholesterol (FOC). Food intake and weight gain was similar in the 4 diet groups, although the fasting blood glucose was lowest in diabetic rats fed BT. Cholesterol supplementation increased intestinal wall and mucosal weights when fed with BT, but the opposite effect was seen with FO, with lower wall and mucosal mass with FOC than with FO. Ileal uptake of D-glucose was lower in FO than in BT or FOC. Cholesterol feeding was associated with enhanced jejunal uptake of cholesterol when fed with BT, but the converse was observed with FO. Thus, 1) the reduction of glucose absorption associated with feeding fish oil is blunted in the presence of a supplemented intake of cholesterol; and 2) a fish oil diet reduces cholesterol uptake even in the presence of a high level of dietary cholesterol. It remains to be established what is the optimal ratio of dietary saturated, polyunsaturated omega-3 and omega-6 fatty acids, and cholesterol required to normalize intestinal transport function in diabetic rats.

Animals↗
PubMed1984

[Intestinal absorption of calcium and its regulation. Tissue, membrane and molecular events].

The intestinal absorption of calcium involves an active transport against an electrochemical gradient, a saturable and a nonsaturable transfer following the gradient. The active and the saturable components are transcellular, the nonsaturable component is partly paracellular. Calcium transfer through the intestinal cell includes three steps: 1) the "down-hill" crossing of the brush-border implies binding to specific sites, carrier-mediated transport using channels or carrier proteins specific to Ca and dependent upon composition phosphorylations alkaline phosphatases; the phospholipid composition of the brush-border also plays a role; 2) the intracellular transfer is characterized by an uptake by such organelles as mitochondria, lysosomes and Golgi vesicles and by a transfer on a specific calcium-binding protein; 3) the "up-hill" transfer across the baso-lateral membrane requires energy and energy is mediated by an ATP-activated Ca2+ pump and a Na+/Ca2+ antiport. 1.25 dihydroxycholecalciferol, steroid hormone synthetized from vitamin D3 is the major direct regulator of Ca absorption: in the vitamin D-deprived animal, it increases the selective permeability for Ca of the brush-border, induces the synthesis of proteins after genomic transcription, activates the Ca-ATPases, and acts as a trophic hormone. The other hormones principally act by modulation of the renal biosynthesis of 1.25 dihydroxycholecalciferol. The efficiency of Ca absorption depends on site, with duodenum greater than jejunum greater than caecum greater than ileum. Dietary constituents such as carbohydrates and amino acids increase Ca absorption whereas phytic acid and excess of phosphorus decrease it. They act by modifying Ca bioavailability and perhaps brush-border permeability. Adaptation to increased demand occurs during growth, pregnancy and lactation in normal states but disappears during vitamin D deficiency. In man, lowered efficiency with increasing age is often aggravated by a low calcium diet.

Animals↗
PubMed1991

Intestinal absorption of cholecalciferol and 25-hydroxycholecalciferol in patients with both Crohn's disease and intestinal resection.

We compared the intestinal absorption of cholecalciferol and 25-hydroxycholecalciferol in patients with Crohn's disease and resections of the small bowel. Patients were subgrouped into those with small (less than 100 cm), intermediate (100-300 cm), and large (greater than 300 cm) resections. [3H]cholecalciferol or [3H]25-hydroxycholecalciferol were given orally and serial blood samples were taken for measurement of plasma radiolabeled vitamin. Absorption of both forms of the vitamin decreased with extent of resection but 25-hydroxycholecalciferol absorption was always greater than that of cholecalciferol. When compared with normal control subjects, 25-hydroxycholecalciferol absorption in these patients was better maintained than that of cholecalciferol. These data indicate that vitamin D malabsorption reflects the extent of distal small-bowel resection in Crohn's disease. Treatment with oral cholecalciferol is sufficient in those with small or moderate resections but oral 25-hydroxycholecalciferol supplementation may be preferred in those with a severe short-bowel syndrome.

Absorption↗
PubMed1999

Distribution characteristics of entrapped recombinant human erythropoietin in liposomes and its intestinal absorption in rats.

Recombinant human erythropoietin (Epo) is frequently administered by intravenous (i.v.) injection for the clinical treatment of renal anemia. Oral (per os; p.o.) administration is desired as an alternative route to i.v. administration, and liposomes have been chosen as a drug carrier. We found previously that after a p.o. administration to rats of Epo entrapped in liposomes before gel filtration, the Epo was absorbed, but variability in the number of days of appearance and in the levels of pharmacological effects, i.e. , the peak of circulating reticulocyte counts (RTC), was observed. The purpose of the present study was to examine the distribution characteristics of Epo in liposomes and intestinal absorption of liposomal Epo in rats by using purified Epo entrapped in liposomes after gel filtration (Epo/liposomes). The distribution characteristics of Epo/liposomes were determined by measuring the Epo in liposomes by a radioimmunoassay, high-performance liquid chromatography and zeta potential measurements. We observed that the protein part of Epo was mostly entrapped in liposomes, and was not adsorbed by the liposomal membrane at middle and high Epo p.o. doses, but the zeta potential of the Epo/liposomes increased negatively with the increase in the Epo p.o. doses. These results suggest that the sialic acid part of Epo entrapped in liposomes may project out from liposomes, depending on the entrapped Epo concentration. Little Epo was adsorbed or penetrated into liposomes when it was added to empty liposomes. After the p. o. administration of Epo/liposomes, the peak of RTC appeared at a 2-day delay on day 6, without variation and without dose dependency in comparison with that after i.v. administration. These results suggest that one of the reasons for the variability may be because the non-entrapped Epo and/or Epo/liposomes itself affected the intestinal absorption of Epo/liposomes. In conclusion, Epo/liposomes without nonentrapped Epo may be clinically useful for the oral administration of Epo.

Administration, Oral↗
PubMed2000

Intestinal absorption of octreotide: N-trimethyl chitosan chloride (TMC) ameliorates the permeability and absorption properties of the somatostatin analogue in vitro and in vivo.

Octreotide acetate is a somatostatin analogue used for the control of endocrine tumors of the gastrointestinal (GI) tract and the treatment of acromegaly. The oral absorption of octreotide is limited because of the limited permeation across the intestinal epithelium. Both chitosan hydrochloride and N-trimethyl chitosan chloride (TMC), a quaternized chitosan derivative, are nonabsorbable and nontoxic polymers that have been proven to effectively increase the permeation of hydrophilic macromolecules across mucosal epithelia by opening the tight junctions. This study investigates the intestinal absorption of octreotide when it is coadministered with the polycationic absorption enhancer TMC. Caco-2 cell monolayers were used as an in vitro intestinal epithelium model, and male Wistar rats were used for in vivo studies. Octreotide with or without polymers (TMC; chitosan hydrochloride) was administered intrajejunally in rats, and serum peptide levels were measured by radioimmunoassay. All applications and administrations were performed at neutral pH values (i.e., pH = 7.4). In vitro transport studies with Caco-2 cells revealed an increased permeation of octreotide in the presence of TMC. Enhancement ratios ranged from 34 to 121 with increasing concentrations of the polymer (0.25-1.5%, w/v). In rats, 1.0% (w/v) TMC solution significantly increased the absorption of the peptide analogue, resulting in a 5-fold increase of octreotide bioavailability compared with the controls (octreotide alone). Coadministration of 1.0% (w/v) chitosan hydrochloride did not enhance octreotide bioavailability. These results in combination with the nontoxic character of TMC suggest that this polymer is a promising excipient in the development of solid dosage forms for the peroral delivery and intestinal absorption of octreotide.

Algorithms↗
PubMed1988

In vitro model for ciclosporin intestinal absorption in lipid vehicles.

The influence of lipid vehicles on the intestinal absorption of Ciclosporin was studied in vitro. The effect of the intestinal lipid digestion was considered on the partition of the drug from olive oil or middle-chain triglyceride (MCT) into phases of simulated intestinal content. The phases obtained after ultracentrifugation were analyzed for their Ciclosporin content and characterized for their lipid classes. For both lipid vehicles the presence of lipolysis products did not promote the partition of the drug into the aqueous phase. The absorption in vivo was not related to the drug amount in the aqueous phase and in the oil phase. Therefore, phase quantification in vitro cannot simulate the dynamics of in vivo absorption events following application of a poorly water-soluble drug in a lipid vehicle.

Chemical Phenomena↗