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Results for “Intestinal Absorption”

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At least 199 records · Page 11Linked to original sources

PubMed1991

The intestinal absorption of 3-O-methyl-D-glucose in methotrexate-treated rats: an in vivo study of small bowel function.

The in vivo absorption of 3-O-methyl-D-glucose (3MG) as a marker of intestinal function has not been studied in an animal model. We evaluated the use of 3MG as a marker of intestinal absorption when given enterally to rats recovering from small bowel mucosal injury induced by methotrexate (MTX). Radiolabeled 3MG was administered into the duodenum of control (CON) and MTX-treated rats and blood samples were obtained at specified intervals. Mucosal permeability was also assessed using radiolabeled mannitol and polyethylene glycol 900 (PEG). Concentration time points were plotted, and area under the curve was calculated as an approximation of absorbed dose. Mucosal weight, maltase activity, and protein content were determined on mucosal scrapings. During the acute phase (day 5), 3MG absorption and maltase-specific activity were significantly decreased in the MTX group when compared to the CON group (p less than 0.001). The MTX group showed a trend toward greater permeability to mannitol when compared to the CON group; however, this was not statistically significant. Mucosal permeability to PEG was similar in both groups. During a later stage in the recovery process (day 12), the area under the curve calculations for 3MG absorption were the same for both CON and MTX animals, with maltase activity in the MTX group recovering to control values. Changes in 3MG absorption paralleled total maltase activities following severe injury. These results suggest that the combined active and passive transport of 3MG in vivo could be of use as a marker of intestinal absorption in states where the small intestine has sustained major damage resulting in compromised absorption as well as brush border digestion.

3-O-Methylglucose↗

PubMed1997

[Molecular characterization of intestinal absorption of drugs by carrier-mediated transport mechanisms].

It has long been thought that intestinal absorption of most of the drugs proceeds by passive diffusion mechanism, in which lipid solubility of the drug molecule is a determinant factor. However, water-soluble natural compounds such as amino acids and sugars can move across cell membranes by the specialized carrier-mediated transport mechanisms. Although some drugs which are structurally analogous to natural compounds have been suggested to be absorbed by such transporters, no clear evidence for the involvement of carrier-mediated transport mechanisms has been obtained. In the present study, through the approach by means of the molecular cloning and functional expression of drug transporters as well as membrane physiological analysis for the drug transport across the intestinal epithelial cell membranes, participation of the carrier-mediated transport mechanisms for the drug absorption was clarified. They include peptide transporter, monocarboxylic acid transporter, anion antiporter, and P-glycoprotein. Most of them have a function for the uptake of drugs into epithelial cells, leading to the increased absorption of drugs, whereas P-glycoprotein excludes drugs into the lumen, thereby decreasing the apparent absorbability of drugs. A rat intestinal monocarboxylic acid-proton cotransporter, MCT1, and an anion antiporter, AE2, were suggested to contribute to the pH-dependent intestinal absorption of monocarboxylic acids such as benzoic acid, lactic acid, nicotinic acid, and valproic acid. An involvement of such pH-dependent transporters in the intestinal absorption of weak organic acids is important, because they may have an alternative mechanism against passive diffusion according to the pH-partition hypothesis. PepT1 cloned from rat intestinal epithelial cells as a peptide transporter was clarified to localize at the intestinal epithelia brush-border membrane and to function for the absorption of beta-lactam antibiotics by the proton-gradient energized mechanism. In contrast, P-glycoprotein functions for the secretion of drugs into the intestinal lumen, thereby decreasing intestinal absorption of an immunosuppressive, cyclosporin A and a 5-HT3 receptor antagonist, azasetron. These lines of studies on the clarification of carrier-mediated drug absorption mechanisms will provide new knowledge for the strategies to the enhancement of intestinal absorption of drugs.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1983

Portal hemodynamics, intestinal absorption, and postshunt encephalopathy.

Although total diversion of portal blood flow has been considered to be the main factor leading to encephalopathy following nonselective shunt (NSS), increased intestinal absorption of cerebral toxins secondary to mesenteric venous decompression could also play a role. Conversely, the low frequency of encephalopathy after the distal splenorenal shunt (DSRS) may be due to preservation of both hepatic portal perfusion and mesenteric venous hypertension. Portal hemodynamics, intestinal absorption of D-xylose, ammonia metabolism, and clinical encephalopathy were assessed preoperatively and in the early and late postoperative periods in cirrhotic patients selected for the DSRS (n = 12) and NSS (n = 10). Preoperatively, NSS patients had significantly less hepatopetal portal blood flow (P = 0.03) and lower D-xylose absorption (P = 0.004) than DSRS patients. DSRS resulted in no significant alterations in hepatic portal perfusion, portal pressure, D-xylose absorption, fasting blood ammonia (NH3), or tolerance to an oral dose of ammonium chloride. In contrast, NSS resulted in complete portal diversion and decompression and significant enhancement of D-xylose absorption on both the early (P = 0.02) and late (P = 0.03) postoperative evaluations. Early and late postoperative levels of MH3 were significantly higher in NSS patients. Encephalopathy was more frequent after NSS (80%) than after DSRS (17%, P = 0.003). When all patients were considered, preoperative to early DSRS (17%, P = 0.003). When all patients were considered, preoperative to early postoperative change in NH3 correlated with change in D-xylose absorption (r = 0.52, p = 0.02), and there were significantly more individuals with a greater than 2 gm increase in D-xylose absorption who developed encephalopathy (83%) than patients with no or minimal increase in D-xylose absorption (33%, P = 0.04). The results of this study suggest that altered intestinal absorption may be one of many factors determining postshunt cerebral function.

Ammonia↗

PubMed1981

Intestinal absorption of calcium: role of dietary phosphate and vitamin D.

The intestinal absorption of calcium (Ca) has been shown to depend on vitamin D3, 1,25-dihydroxyvitamin D3 [1,25(OH)2D3], and dietary phosphorus (P) concentration. This study was designed to evaluate the role of dietary P independent of vitamin D3 or 1,25(OH)2D3. Vitamin D-deficient rats were studied during dietary P restriction and were compared with control groups raised on a normal-phosphorus diet (NP). Balance studies were sued. Net intestinal Ca absorption was significantly lower with dietary P restriction compared with the NP group. This malabsorption of Ca was corrected by the administration of either D3 for 1,25(OH)2D3, despite hypophosphatemia. Everted gut sacs showed a marked reduction in the uptake of 45Ca in the duodenum, jejunum, and ileum during dietary P restriction. We concluded that dietary P concentration plays a major role in intestinal Ca absorption in the vitamin D-deficient rats. These findings suggest an effect of the low-phosphate diet on the vitamin D-dependent, Ca-transport mechanism.

Animals↗

PubMed1984

Intestinal absorption of ST-1435 in rats.

The intestinal absorption of a 19-norprogesterone (ST-1435) was studied in rats after an oral dose of 5 mg ST-1435/kg body weight. Blood samples were collected simultaneously from the portal vein and by cardiac puncture. Plasma ST-1435 concentrations were measured from the samples by radioimmunoassay (RIA). Chromatographic purification of ST-1435 in rat plasma revealed a metabolite cross-reacting in the RIA. A peak concentration of 240 ng ST-1435/ml was found in portal plasma 75 minutes after administration, indicating that the steroid is well absorbed from the small intestine. However, in spite of the relatively high dose used, the plasma concentrations of ST-1435 in the systemic circulation remained low and of short duration. Thus, it seems that ST-1435 in hepatic portal blood is extensively taken-up and metabolized by the liver, resulting in low plasma concentrations of ST-1435 in the systemic circulation when the steroid is administered orally. This is also supported by the observation that higher metabolite levels were found in systemic plasma than in portal plasma during the first 90 minutes after administration. This pronounced first-pass effect may also explain why in women oral administration of ST-1435 has failed to result in any biological effect.

Administration, Oral↗

PubMed1993

Development of new lipophilic derivatives of tetragastrin: physicochemical characteristics and intestinal absorption of acyl-tetragastrin derivatives in rats.

In order to improve the intestinal absorption of tetragastrin (TG), we synthesized lipophilic derivatives of TG by acylation of its N-terminal amino group with acetic acid, caproic acid, and lauric acid. The purified TG derivatives, acetyl-tetragastrin (Ac-TG), caproyl-tetragastrin (Cap-TG), and lauroyl-tetragastrin (Lau-TG), were confirmed to be more lipophilic than the parent TG by high-performance liquid chromatography (HPLC). The pharmacological activities and the intestinal absorption of TG and its derivatives were examined by measuring gastric acid secretion. Stimulation of gastric acid secretion by these derivatives after intravenous administration was stronger than with native TG. When the acetyl- and caproyl-derivatives were administered into the large intestinal loops, a marked increase in gastric acid secretion was observed in comparison with TG, while no significant effect occurred following administration of the TG derivatives into the small intestines. These results indicated that chemical modification of TG with fatty acids improves the absorption of TG from the large intestines.

Acetates↗

PubMed1969

Effect of bile acids on the intestinal absorption of endotoxin in rats.

The absorption of tritium-labeled Escherichia coli O89 Westphal-type endotoxin from the peritoneal cavity of rats was diminished by bile by 23% and by sodium deoxycholate by 47%, respectively. Practically, there is no endotoxin absorption from the intestinal tract of normal rats. The bile duct of rats was chronically cannulated for experimental purposes. A significant amount of perorally administered endotoxin absorbed from the intestinal canal into the blood in the rats treated thus. Absorption was demonstrated by the lethal effect of endotoxin on rats previously hypersensitized by lead acetate, and by the radioactivities found in the blood samples. The intestinal absorption of endotoxin in rats, rendered bile-deficient, may be prevented by sodium deoxycholate. Supported by their experimental findings, we emphasize the important role of bile acids in the defense mechanism of the macroorganism against bacterial endotoxins.

Animals↗

PubMed1975

Effects of dietary lactose and lactase preparation on the intestinal absorption of calcium and magnesium in normal infants.

Effects of dietary lactose and a lactase preparation on the intestinal absorption of calcium and magnesium were studied in 3 groups under 8 months of age; infants on a proprietary milk, infants on a lactose-free milk, and infants on a proprietary milk to which a lactase preparation was added. The intestinal absorption of both elements was reduced in infants on a lactose-free milk and enhanced in infants who were fed on a proprietary milk and given a lactase preparation.

Animals↗

PubMed1980

Binding of cationized ferritin to the cell-coat glycoproteins of human and rat small-intestinal absorptive cells.

The binding of cationized ferritin (CF) to the cell-coat (glycocalyx) glycoproteins of human and rat intestinal absorptive cells was investigated in relation to the amount of sialic acid in these macromolecules. The cell coat of human absorptive cells exhibited poor binding of CF and contained a small amount of sialic acid. The cell coat of rat absorptive cells had about ten times more sialic acid than that of human cells and showed a strong affinity for the marker. The removal of sialic acid from the cell-coat glycoproteins of rat intestinal cells by neuraminidase treatment abolished CF binding. These results suggest that sialic acid is necessary for CF binding and that human and rat intestinal absorptive cells show a species-specific difference in the sugar composition of the cell coat.

Animals↗

PubMed1979

Intestinal absorption and lymphatic transport of cholesterol and beta-sitostanol in the rat.

The intestinal absorption of cholesterol and beta-sitostanol (the saturated analogue of beta-sitosterol) were measured and their absorptions compared in the presence and absence of cholestyramine. After test meals containing [(3)H]cholesterol and [(14)C]beta-sitostanol without added cholestyramine, 4-day fecal collections yielded an average of 51% of the fed cholesterol and 83% of the fed beta-sitostanol. In separate lymph transport studies without cholestyramine, 36% of the fed cholesterol was recovered in lymph in 24 hours compared to only 2% of the fed beta-sitostanol. Thus, while total recoveries of the two labeled compounds in feces plus lymph were nearly identical (51% + 36% = 87% for cholesterol and 83% + 2% = 85% for beta-sitostanol) their distribution in the two compartments was markedly different, reflecting the relative nonabsorbability of beta-sitostanol. Adding cholestyramine to the test meal caused fecal excretion of cholesterol to increase to 73%, independent of the dose of cholestyramine used. Cholestyramine had no effect on the fecal excretion of beta-sitostanol (average excretion after cholestyramine, 85%). The relative non-absorbability of beta-sitostanol compared to cholesterol is clearly evident in this study and leads us to suggest its possible use as a lipid-soluble, nonabsorbable reference compound for measurement of the absorption of cholesterol and other lipids. Further data are presented to justify its use for this purpose.-Hassan, A. S., and A. J. Rampone. Intestinal absorption and lymphatic transport of cholesterol and beta-sitostanol in the rat.

Animals↗

PubMed1989

Intestinal absorption of stearic acid after consumption of high fat meals in humans.

The intestinal absorption of stearic acid (18:0), relative to other fatty acids, was evaluated in a group of 10 normal volunteers. Subjects were fed two types of high fat meals; one contained a relatively high content of stearic acid and the other a relatively low content. Plasma chylomicrons were isolated at 2, 4, 6 and 8 h after ingestion of the meals. Fatty acid patterns of chylomicron lipids were determined, and relative intestinal absorption rates of each fatty acid were estimated by comparing the fatty acid composition of chylomicron lipids with that of the fat in the meals. Overall, for both meals the fatty acid pattern of chylomicron lipids was very similar to that of ingested fat. Percentages of palmitic acid (16:0) and stearic acid, relative to other fatty acids, were only slightly lower in chylomicron lipids than in the meal fat. These data suggest that intestinal absorbability of stearic acid is similar to that of palmitic acid, and both saturated fatty acids appear to be absorbed almost as well as oleic acid (16:1).

Adult↗

PubMed1991

The effect of exercise associated with subchronic poisoning with potassium nitrate and sodium nitrite on the processes of intestinal absorption of D-xylose in rats.

The intestinal absorption of D-xylose was studied during the subchronic poisoning of male Wistar rats with orally administered potassium nitrate and sodium nitrite associated with exercise; running on a moving track during the last two weeks of poisoning. The metabolic parameters of Na+/K(+)-ATPase, alkaline phosphatase, oxygen uptake, and lactic acid level in the small intestine mucosa were determined one hour after D-xylose treatment. Exercise increased the toxicity of potassium nitrate and sodium nitrite. The experiment demonstrated post-exercise reduction of D-xylose absorption and decrease activity of Na+/K(+)-ATPase and alkaline phosphatase. Exercise caused transient hypoxia of the small intestine, which was observed only in the groups subjected to exercise on the day of the determinations.

Administration, Oral↗

PubMed1994

Intestinal absorption of vitamin A in streptozotocin-induced diabetic rats.

Diabetes mellitus is known to be associated with enhanced intestinal absorption of lipids. A validated in vitro technique was used to examine the uptake of (3H) retinol (a lipid soluble vitamin) into the jejunum and ileum of streptozotocin (STZ)-induced diabetic rats. In addition, availability of vitamin A in the plasma and liver of diabetics which were pair-fed to non-diabetic control rats was investigated. The relationship between the duration of incubation and retinol uptake was curvilinear in both the jejunum and the ileum, but no difference in intestinal uptake was observed between the two groups of animals. A linear relationship was noted between the concentration of retinol and uptake into both the jejunum and ileum. There was no difference in the uptake of retinol between the diabetic and control animals. The hepatic concentration of vitamin A also remained unaffected by diabetes as indicated by similar values found between pair-fed diabetic and non-diabetic control rats. Unlike the liver, plasma retinol level was decreased in the diabetic animals; this effect does not appear to be caused by any change in the intestinal absorption of the vitamin.

Animals↗

PubMed1995

Biodiscrimination of alpha-tocopherol stereoisomers during intestinal absorption.

Synthetic alpha-tocopherol (alpha-Toc) contains equal amounts of eight different stereoisomers, and the four stereoisomers with the 2R configuration are generally more active than their corresponding 2S-isomers. We investigated the biodiscrimination of alpha-Toc stereoisomers during intestinal absorption in situ and in vitro. Intestinal absorption of alpha-Toc stereoisomers was examined in situ in vitamin E-deficient rats with cannulated thoracic ducts. We found that the ratios of alpha-Toc stereoisomers in lymph of the all-rac-alpha-Toc group were the same as the administered alpha-Toc stereoisomers, and 2R-isomers occupied approximately 50% of absorbed alpha-Toc. The uptake of alpha-Toc stereoisomers also was measured using Caco-2 cells cultured on filter membranes. The concentration of RRR-alpha-Toc in Caco-2 cells was not significantly different from that of SRR-alpha-Toc. Therefore, the discrimination of alpha-Toc stereoisomers does not occur during absorption in small intestine, suggesting the liver as source for the biodiscrimination.

Animals↗

PubMedDate not supplied

Intestinal absorption of thiamine, glucose and sodium in rats after lead and joint lead-zinc treatment.

Intestinal absorption of thiamine, glucose and sodium was studied by perfusion method in situ in control rats, in rats subchronically poisoned with lead and in rats subchronically poisoned with lead and zinc administered jointly. In lead poisoned rats absorption of the investigated substances was increased. In lead and zinc poisoned rats intestinal absorption was not elevated. This seems to indicate that interaction between lead and zinc was antagonistic also when the metals were administered parenterally.

Animals↗

PubMed1985

In vivo intestinal absorption of selenate and selenite by rats.

Intestinal absorption of selenate and selenite was investigated in rats by using an in vivo perfusion technique. Different segments of the intestine were perfused with an isotonic solution containing different concentrations of SeO42- or SeO32-. The site of greatest SeO42- absorption was found to be the ileum followed in descending order by the proximal jejunum and large intestine (cecum and colon). Furthermore, SeO42- was absorbed significantly faster from the ileum than SeO32-. The concentration dependence of SeO42- absorption indicates that SeO42- is absorbed by a saturable transport mechanism of the ileal mucosa. Absorption of SeO42- at a concentration of 0.01 mM was not affected by the presence of 1 mM SeO42- in the perfusate. When the SeO42- concentration of the perfusate was increased to 1 mM, the absorptive functions of the ileal epithelium appeared to be generally impaired. It is concluded that selenate is absorbed from the ileum by a carrier-mediated mechanism.

Animals↗

PubMed1997

Effects of silicon, citrate and the fasting state on the intestinal absorption of aluminium in rats.

1. The effect of silicon (Si) contained in drinking water and solid food on the intestinal absorption of aluminium (Al) remains a matter of debate. The present study was designed to readdress this issue in the experimental animal, and to examine concomitantly the effects of citrate and the fasting state, respectively. 2. Three groups of young, non-fasted rats (n = 8 per group) were gavaged by solutions containing 3.8 ng of 26Al, 63 ng of 27Al, and either distilled water (< 0.1 mg/l Si) or commercial mineral water with a medium (6 mg/l) or high (14 mg/l) Si concentration. 3. Two other groups of eight non-fasted rats each received the same distilled water or high-Si gavage solution, respectively, together with a high citrate concentration (62 g/l). In each case the animals had free access to drinking water for 5 days before and 2 days after the gavage, containing the same Si concentration as in the gavage solution. A sixth group of eight rats was gavaged by low-Si, Al and distilled water in the fasted state. 4. The animals were killed 48 h after gavage, and blood, tissue and urine samples were collected for 26Al measurements by accelerator mass spectrometry. 5. We found that the fraction of absorbed 26Al retained in the skeleton (0.025-0.030%) was of the same order of magnitude as the fraction excreted in the 48 h urine (0.035-0.037%). High Si concentrations in the drinking water failed to depress the 26Al fraction absorbed, as estimated on the basis of skeletal accumulation and urinary excretion. 6. The administration of citrate-containing fluid enhanced 26Al absorption 5- to 10-fold (P < 0.005), but again the Si content of drinking water did not interfere. Finally, the intestinal absorption of 26Al was approximately 15 times higher in the fasted than in the non-fasted state. 7. In conclusion, the provision of large amounts of Si in the drinking water failed to modify physiological intestinal Al absorption under basal conditions or after its stimulation by citrate. However, a prolonged fast greatly enhanced Al absorption, compared with the non-fasted state.

Aluminum↗

PubMed1989

The intestinal absorption of dietary folates in health and disease.

Dietary folates exist as pteroylpolyglutamates (PteGlun) that undergo hydrolysis to pteroylmonoglutamate (PteGlu) forms during the process of intestinal absorption. Using the technique of jejunal perfusion of separately labeled folates, our laboratory has demonstrated that hydrolysis of PteGlun occurs on the surface of the jejunum and is a prerequisite for folate absorption. An intestinal brush border pteroylpolyglutamate hydrolase (BB-PPH) has been identified in human and pig jejunum with characteristics that are distinct from those of an intracellular hydrolase (IC-PPH). Functional parallels of BB-PPH with in vivo hydrolysis of PteGlun in human and pig intestine and the clinical responsiveness of BB-PPH to different disease states indicate that this enzyme plays the major physiological role in folate absorption. Folate malabsorption is found in diseases which affect the jejunal mucosa and in response to various drugs. In most of these clinical conditions, folate malabsorption results from suppression of both of the processes of hydrolysis of PteGlun and jejunal uptake of PteGlu. Ongoing studies in miniature pigs are aimed at definition of the sequence of development of folate malabsorption in chronic alcoholism.

Animals↗