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PubMed1984

Intracisternal granules in the intestinal absorptive cells in mice.

A new type of cytoplasmic granules was demonstrated with the electron microscope in a substantial percentage of absorptive cells in the small intestine of standard-fed, fasted and oil-fed CFW/L1 mice, and extremely rarely in standard-fed Balb/C mice. The granules appeared as the accumulations of electron-dense material within the distended cisternae of the rough endoplasmic reticulum. Most of the intracisternal granules were situated in the basal part of the cell, close to the nucleus. The diameter of the granules ranged from 0.24/micron to 0.96/micron.

Animals↗
PubMed1992

Effects of the mucoadhesive polymer polycarbophil on the intestinal absorption of a peptide drug in the rat.

The absorption across rat intestinal tissue of the model peptide drug 9-desglycinamide, 8-arginine vasopressin from bioadhesive formulations was studied in-vitro, in a chronically isolated internal loop in-situ and after intraduodenal administration in-vivo. A controlled-release bioadhesive drug delivery system was tested, consisting of microspheres of poly(2-hydroxyethyl methacrylate) with a mucoadhesive Polycarbophil-coating, as well as fast-release formulation consisting of an aqueous solution of the peptide in a suspension of Polycarbophil particles. Using the controlled-release system, a slight improvement of peptide absorption was found in-vitro in comparison with a non-adhesive control system, but not in-situ or in-vivo. In contrast, bioavailability was significantly increased in all three models from the Polycarbophil suspension in comparison with a solution of the drug in saline. The effect appeared to be dose-dependent, indicative of intrinsic penetration-enhancing properties of the mucoadhesive polymer. A prolongation of the absorption phase in-vitro and in the chronically isolated loop in-situ suggested that the polymer was able to protect the peptide from proteolytic degradation. This could be confirmed by degradation studies in-vitro. The duration of the penetration enhancing/enzyme inhibiting effect was diminished with increasing complexity of the test model, in the same way as was previously found for the bioadhesive effect. This interrelationship suggests that the observed improvement in peptide absorption and the mucoadhesive properties of this polymer are associated. The development of a fast-release oral dosage form for peptide drugs on the basis of Polycarbophil appears to be possible.

Acrylic Resins↗
PubMed1980

Total body retention and intestinal absorption of orally administered calcium-47 in chronic hemodialysis patients.

In order to evaluate the intestinal absorption of calcium in end-stage renal disease, whole-body 47Ca retention was determined using a whole-body counter in 18 patients undergoing chronic hemodialysis and in 12 normal volunteers. The results of the above study were compared with those obtained by measuring plasma radioactivity after oral load of 47Ca. A significantly lower whole-body retention of 47Ca was found in hemodialysis patients, as compared with normal subjects, and the results were similar to those of the direct calcium-absorption test. These findings suggest that whole-body 47Ca retention can be used as an index of intestinal calcium absorption in patients with chronic renal failure.

Administration, Oral↗
PubMed1987

Intestinal absorption of cadmium and inorganic mercury in the rat: no major involvement of metallothionein.

The intestinal absorption of cadmium and inorganic mercury was studied in adult rats, administered the metal salts intragastrically or parenterally in repeated or single doses. The intestines contained only small proportion of the body burden; no major change was found in the intestinal level of metallothionein, copper and zinc. Therefore, no major role can be ascribed to intestinal metallothionein in limiting absorption of high oral doses of cadmium and mercury.

Animals↗
PubMed1976

Intestinal absorption of polyunsaturated phosphatidylcholine in the rat.

The mechanism of intestinal absorption of polyunsaturated phosphatidylcholine in an oil medium was studied with 1,2-di-[9,10,12,13-3H4]linoleoyl-sn-glycero-3-phospho-[N-14CH3]-choline, 1-[1-14C]linoleoyl-2-[9,10,12,13-3H4]-linoleoyl- and 1-[9,10,12,13-3H4]linoleoyl-2-[1-14C]linoleoyl-sn-glycero-3-phosphocholine, especially with regard to the stability of the ester bonds in position 1 and 2 of the phospholipid molecule. The absorption rate, as measured by the disappearance from the gastro-intestinal tract, was comparatively rapid in the first 6 - 8 h, but then became considerably slower. After 24 h more than 90% of the applied radioactivity was absorbed from the intestinal tract. Respiratory 14CO2 from the degradation of the unsaturated acyl moiety in position 2 is produced much more rapidly than that from the acyl group attached to the 1-position of the glycerophosphocholine backbone. Analyses of the liver phosphatidylcholine by specific enzymatic hydrolysis with phospholipase A2, 6 h after the application, showed that in the isolated PC 9 times more labelled fatty acids from the original 1-position were present than from the corresponding 2-position. In rats with lymph fistula it was shown that more than 90% of the acyl moieties of the administered 1,2-di-[9,10,12,-13-3H4]linoleoyl-[N-14CH3] glycerophosphocholine was transported by the chylomicrons. About one half of the 14C choline radioactivity of the glycerophosphocholine backbone was found in the chylomicrons and the other half in the liver. The 3H radioactivity distribution in the chylomicrons amounted to 25% in the phosphatidylcholine fraction and 75% in the neutral lipids. Positional specific analyses of the phosphatidylcholine present in chylomicrons confirmed the fact that the 1-position remained practically intact while the 2-position underwent considerable exchange with unlabelled fatty acids. Analysis of the liver of the animals with lymph fistula indicated that it was practically free of the 3H radioactivity derived from the acyl moieties but contained a high percentage of the 14C radioactivity of the choline group. The methyl groups of choline were oxidized only to a very small extent. These results demonstrate that during the absorption process, about one half of the absorbed polyunsaturated phosphatidylcholine is hydrolyzed to 1-acyl-lysophosphatidylcholine and reacylated again to phosphatidylcholine upon entering the mucosa cell, while the other half is completely hydrolyzed to free fatty acids and glycerophosphocholine or its hydrolysis products. The fatty acids released are utilized for the reassembly of triacylglycerides and phosphatidylcholine found in the chylomicrons.

Animals↗
PubMed1976

Folate content of Iranian breads and the effect of their fiber content on the intestinal absorption of folic acid.

Folate deficiency is a relatively uncommon disorder in central Iran. In order to explain this finding; the acid content of various Iranian breads was determined, since bread is the staple food in Iran. Tanok, the village wholemeal bread, has an average "free" folate content (without conjugase incubation) of 0.34 mug/g. Sangask and Bazari, leavened breads made from flours of high extraction rates and widely consumed in towns and cities, have aberage "free" folate contents of 0.38 and 0.71 mug/g, respectively. The folate content of these breads are significantly higher than that of white bread from refined flour (0.13 mug/g) or oatmeal bread (0.09 mug/g). Iranian breads also have a high content of indigestible fiber (1.6 to 4.2% of dry weight). Since substances within the bread, such as fiber, may interfere with folate absorption by the small intestine, sequential folate absorption tests (tritiated pterolymonoglutamic acid) were performed in four subjects with meals of increasing fiber content and fasting. No interference with folate absorption was found. Furthermore, in vitro studies did not demonstrate the formation of insoluble complexes between bread fiber and folic acid, which might indicate decreased availability.

Bread↗
PubMed1994

Effects of surfactants on amiodarone intestinal absorption. I. Sodium laurylsulfate.

Amiodarone is a widely used antiarrhythmic agent with high variability in therapeutic effects, which appears to be related, at least in part, to its pharmacokinetics, and in particular, gastrointestinal absorption. The drug exhibits physico-chemical properties highly suitable for diffusion across lipophilic absorbing membranes but its low aqueous solubility can act as the rate limiting step for absorption, making it erratic and variable. In studying the intestinal absorption mechanism of amiodarone, a series of experiments using a rat gut in situ preparation was performed in the presence of a synthetic anionic surfactant, as a drug solubilizer, i.e., sodium laurylsulfate, at variable supramicellar concentrations (from 2.6 to 104 mM). Absorption rate constants of amiodarone decreased as surfactant concentration increased, the absorption being unusually fast at lower surfactant concentrations. Equations were developed to evaluate the relationship between absorption rate constant and surfactant concentration in the intestinal luminal fluid.

Amiodarone↗
PubMed2002

Intestinal absorption and presystemic elimination of the prokinetic agent, EM574, in the rabbit.

The purpose of this study was to characterize the pharmacokinetics and dose proportionality of the prokinetic macrolide, EM574, in rabbits following intravenous dosing, and to determine the intestinal absorption and intestinal and hepatic first-pass elimination of EM574 in rabbits. Two doses (0.05 and 0.25 mg/kg) of EM574 were given to rabbits intravenously in a crossover study. In a separate gut perfusion study, rabbit duodenal or jejunal segments were perfused with EM574 solution at 0.2 mL/min for 130 min. Plasma levels of EM574 were determined by a validated LC-MS/MS assay, and concentrations in perfusate were determined by HPLC with UV detection. The absorptive clearance (PeA) of EM574 was calculated from the steady-state rate of disappearance from the gut lumen during perfusion. The cumulative amount (A(app)) of drug appearing in the systemic circulation was calculated by deconvolution, where the input response was the plasma concentration-time profile during intestinal perfusion and the unit impulse response was the mean profile following intravenous bolus dosing to sham-operated rabbits in a separate experiment. F(g)F(h) was calculated from the ratio of A(app) to the total amount disappeared from gut lumen during perfusion. Hepatic first-pass elimination was measured by intraportal venous infusion. EM574 exhibits linear kinetics over the dose range studied. CL, V(ss), and terminal half-life (mean +/- SD) of EM574 were 68.6 +/- 15.5 mL/min/kg, 13.4 +/- 3.0 L/kg, and 2.7 +/- 0.8 h, respectively. EM574 is expected to be absorbed completely from the rabbit small intestine based on its high jejunal PeA values (8.1 +/- 2.2, and 5.5 +/- 1.5 microL/min/cm following low and high dose perfusion, respectively). The first-pass extraction of EM574 was substantial and dose independent. Mean F(g) and F(h) were 0.14 and 0.20, respectively, suggesting that the intestinal and hepatic first-pass elimination of EM574 were comparable. Deconvolution was successfully applied in the determination of gut wall and hepatic first-pass elimination of EM574.

Administration, Oral↗
PubMed2004

The effect of quinidine, used as a probe for the involvement of P-glycoprotein, on the intestinal absorption and pharmacodynamics of methadone.

AIMS: There is considerable unexplained interindividual variability in the methadone dose-effect relationship. The efflux pump P-glycoprotein (P-gp) regulates brain access and intestinal absorption of many drugs. Evidence suggests that methadone is a P-gp substrate in vitro, and P-gp affects methadone analgesia in animals. However the role of P-gp in human methadone disposition and pharmacodynamics is unknown. This investigation tested the hypothesis that the intestinal absorption and pharmacodynamics of oral and intravenous methadone are greater after inhibition of intestinal and brain P-gp, using the P-gp inhibitor quinidine as an in vivo probe. METHODS: Two randomized, double-blind, placebo-controlled, balanced crossover studies were conducted in healthy subjects. Pupil diameters and/or plasma concentrations of methadone and the primary metabolite EDDP were measured after 10 mg intravenous or oral methadone HCl, dosed 1 h after oral quinidine (600 mg) or placebo. RESULTS: Quinidine did not alter the effects of intravenous methadone. Miosis t(max) (0.3 +/- 0.3 vs 0.3 +/- 0.2 h (-0.17, 0.22)), peak (5.3 +/- 0.8 vs 5.1 +/- 1.0 mm (0.39, 0.84)) and AUC vs time (25.0 +/- 5.7 vs 26.8 +/- 7.1 mm h (-6.1, 2.5)) were unchanged (placebo vs quinidine (95% confidence interval on the difference)). Quinidine increased (P < 0.05) plasma methadone concentrations during the absorptive phase, decreased t(max) (2.4 +/- 0.7 vs 1.6 +/- 0.9 h (0.33, 1.2)), and increased peak miosis (3.2 +/- 1.5 vs 4.3 +/- 1.6 mm (-1.96, -0.19)) after oral methadone. The C(max) (55.6 +/- 10.3 vs 59.4 +/- 14.1 ng ml(-1) (-8.5, 0.65)) and AUC of methadone (298 +/- 46 vs 316 +/- 74 ng ml(-1) h (-54, 18)) were unchanged, as were the EDDP : methadone AUC ratios. Quinidine had no effect on the rate constant for transfer of methadone between plasma and effect compartment (k(e0)) (2.6 +/- 2.6 vs 2.5 +/- 1.4 h(-1) (-3.5, 4.2)). CONCLUSIONS: Quinidine increased the plasma concentrations of oral methadone in the absorptive phase and the miosis caused by methadone, suggesting that intestinal P-gp affects oral methadone absorption and hence its clinical effects. Quinidine had no effect on methadone pharmacodynamics after intravenous administration, suggesting that if quinidine is an effective inhibitor of brain P-gp, then P-gp does not appear to be a determinant of the access of methadone to the brain.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1986

Effect of medium-chain glycerides (MGK) on the intestinal absorption and the hepatobiliary transport of bromthymol blue.

The effect of medium chain glyceride (MGK) emulsion on the intestinal absorption and the biliary excretion of bromthymol blue (BTB) was investigated in rats. Extensive tissue accumulation of BTB was reduced when BTB was administered with MGK emulsion formulation. HCO-100, an emulsifier, was also important for the decrease in the tissue accumulation of BTB. The ratios of absorption percent to tissue accumulation percent and to free fraction, not contained in the droplet of emulsion, in MGK emulsion were much greater than that of the control. Pretreatment with BTB-free emulsion reduced BTB absorption under the control, although tissue accumulation was not affected. The absorption appeared to decrease with increase in the time of pretreatment. The effect of leaving treatment after pretreatment on the absorption of BTB was also investigated. With the increase in leaving time after pretreatment, reduced absorption tended to resume to the level of control. The change in monocaprylate content from 54 to 60% in MGK made a difference in BTB absorption and it was suggested that monocaprylate content in MGK was one of the significant factors of MGK emulsion on drug absorption. Bile recovery study was simultaneously carried out with an in situ recirculation experiment. The recovery of BTB into bile tended to decrease. The ratio of recovery percent of BTB into bile to the absorption percent of BTB also decreased extensively, which is possibly another effect of MGK on drug disposition.

Animals↗
PubMed1978

Intestinal absorption of griseofulvin from a triolein digestion mixture in rats.

The intestinal absorption rate of dissolved griseofulvin was determined from: (a) an aqueous phase, (b) an aqueous phase containing a micellar phase composed of taurodeoxycholate, monoolein, and oleic acid, and (c) an aqueous phase containing the micellar phase and emulsified triolein. The triolein digestion mixtures were recirculated through 20-cm segments of in situ rat jejunum. Lipid concentrations were maintained constant by infusing the lipids into the digestion mixture at the same rate as they disappeared. Griseofulvin distribution among the aqueous, micellar, and oil phases was determined by solubility and equilibrium dialysis experiments. Analysis with a linear kinetic model indicated that griseofulvin absorption from the micellar and oil phases was negligible compared to its absorption from the aqueous phase.

Animals↗
PubMed1990

Intestinal absorption of drugs. III. The influence of taurocholate on the disappearance kinetics of hydrophilic and lipophilic drugs from the small intestine of the rat.

The influence of sodium taurocholate (TC) on the intestinal absorption of drugs was studied in vivo in a chronically isolated internal loop in the rat. The hydrophilic drugs paracetamol (PA) and theophylline (TP) and the lipophilic drugs griseofulvin (GF) and ketoconazole (KE) were used as model drugs. The drug concentrations were kept below the saturation concentration. Absorption kinetics of the drugs were evaluated on the basis of disappearance rates of the drug from luminal solutions in the intestinal loop. Concentrations of TC above the critical micelle concentration (CMC) did not affect the absorption rate of the hydrophilic drugs PA and TP; the barrier function of the intestinal wall for PA and TP was not altered in the presence of taurocholate. The addition of concentrations of TC above the CMC in the perfusion solution resulted in a reduction of the absorption rate of GF and KE. The reduction in the absorption kinetics of GF in the presence of TC correlated well with the reduction of the drug-free fraction in solution due to micellar solubilization. For KE this relation was less clear. It was not possible to determine, on the basis of the phase-separation model, to what extent the fraction of the drug incorporated in TC micelles contributes to the overall diffusion of GF and KE across the preepithelial diffusion barrier. It was concluded that TC exhibits only a minor, if not negligible, effect on the barrier function of the aqueous diffusion barrier adjacent to the intestinal wall.

Acetaminophen↗
PubMed1989

Relationship between the first-order intestinal absorption rate constant in vivo and the membrane permeability clearance in a perfusion system: an intragastric administration method in vivo.

In an attempt to explore the quantitative relation in the intestinal absorption between in vivo and a perfusion system, time courses of the remaining fraction in the stomach and that in the small intestine following the intragastric administration of drug solution to rats were simultaneously analyzed by a linear compartment model, using L-glucose and 3-O-methyl-D-glucose (3-O-MG) as model compounds. Derived first-order gastric emptying rate constant (kg) and first-order intestinal absorption rate constant (ka) were 0.025 and 0.018 min-1, respectively, for L-glucose and 0.033 and 0.275 min-1, respectively, for 3-O-MG. Values of the membrane permeability clearance (CLa,m) estimated in the perfusion system were 0.71 and 3.00 microliters/min/cm, respectively, for L-glucose and 3-O-MG. The operational luminal volume (Vo), given as CLa,m/Ka, of 39 microliters/cm for L-glucose was in agreement with the actual luminal volume in vivo estimated by a inulin dilution method and ranging from 20 to 60 microliters/cm, supporting the idea that CLa,m quantitatively reflects the intestinal membrane permeability in vivo and that the luminal volume in vivo is the primary factor which correlates CLa,m and Ka. The Vo of 11 microliters/cm for 3-O-MG was smaller, though still in the same order. It was also shown that the gastrointestinal absorption of 3-O-MG was gastric emptying limited.

3-O-Methylglucose↗
PubMed1995

Amoxicillin intestinal absorption reduction by amiloride: possible role of the Na(+) -H+ exchanger.

Intestinal absorption of beta-lactam antibiotics has been shown to use the dipeptide carrier system. In vitro experiments have established that the efficiency of uptake by enterocytes depends on an inwardly directed proton gradient--dipeptides and beta-lactam antibiotics being cotransported along with hydrogen ion. This gradient is thought to result from the sodium-hydrogen (Na(+)-H+) exchanger located on the brush-border membrane. The aim of the present study was to assess the in vivo relevance of these data in humans by examining the effect of amiloride, a well-known inhibitor of the Na(+) -H+ exchanger, on the bioavailability of amoxicillin in eight healthy volunteers. The results show that amiloride reduces significantly amoxicillin absorption rate (mean time to maximum concentration increases from 1.0 to 1.6 hours, p < 0.05) and absolute bioavailability (by 27%, p < 0.01) and that amiloride-induced inhibition of the intestinal Na(+) -H+ exchange could be associated with an additional inhibitory effect on (Na/K)-ATPase activity. The present data seem to confirm the role of Na(+) -H+ exchange in the uptake of beta-lactams by the intestine and to support the indirect sodium dependence of this carrier system in vivo.

Adult↗
PubMed1991

Intestinal absorption of calcium from yogurt in lactase-deficient subjects.

Fractional intestinal absorption of calcium (FACa) was measured using radioactive calcium and 200 mg of calcium carrier provided either by yogurt or by CaCl2 in 7 lactase-deficient (L(-] and 7 normal (L(+] subjects. During the control period prior to yogurt consumption, mean calcium intake was 819 mg per day in L(-) and 931 mg per day in L(+) subjects (NS). In both groups of subjects yogurt increased FACa from 20.8 +/- 3.9% to 26.9 +/- 7.2% (P = 0.065) in L(+) subjects and from 20.2 +/- 5.6% to 23.5 +/- 6.4% (P = 0.050) in L(-) subjects. The significant increase in FACa observed in L(-) subjects indicates that yogurt, which is an autodigesting source of lactose, does not impair calcium absorption. FACa increase could reflect the lower dietary calcium intake in L(-) subjects when compared with L(+) subjects, due to avoidance of milk and non-fermented dairy products which could cause intestinal discomfort. It is concluded that yogurt is a well-tolerated and efficient source of calcium in subjects with lactase deficiency.

Adult↗
PubMed1983

Intestinal absorption of levodopa in man.

In four healthy subjects the intestinal absorption of levodopa (l-dopa) was investigated by measuring the plasma concentration of the amino acid following the administration of l-dopa at three different sites in the small intestine. In order to minimize presystemic clearance of l-dopa, the subjects were pretreated with the peripheral decarboxylase inhibitor benserazide 3 X 50 mg every 8 h on the previous day and 1 X 50 mg 2 h prior to administration of the l-dopa. L-dopa 100 mg dissolved in 0.05 N HCl and 50 mg benserazide dissolved in 0.05 N HCl were coadministered. Under these conditions no difference in tmax, cmax or AUC of l-dopa was observed between administration of the drug into the proximal or the distal part of duodenum, or into the upper part of jejunum. The results indicate that in healthy subjects, during inhibition of peripheral decarboxylase, the rate and extent of l-dopa absorption does not differ at any site in the upper small intestine.

Adult↗