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4) The absorption behavior of cyclosporin A lecithin vesicles in rat intestinal tissue. 8) Mechanisms and sites of mannitol permeability of small and large intestine in the rat. 9) Mechanisms of polyethylene glycol 400 permeability of perfused rat intestine. 10) Absorption of 14C-clanobutin-Na isolated perfused intestinal segments in vitro of rats.
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An improved everted gut sac as a simple and accurate technique to measure paracellular transport across the small intestine. Barthe L, Woodley JF, Kenworthy S, Houin G. Equipe Cinetique des Xenobiotiques, Faculta des Sciences Pharmaceutiques, Toulouse, France. An improved everted gut sac system has been developed in which the sacs were carefully prepared from rat small intestine and incubated in tissue culture medium. Under these conditions, the tissue showed good morphology at the electron microscope level, and was metabolically active for up to 2 h at 37 degrees C. Mannitol, an established probe of paracellular transport, was transported from the mucosal to the serosal side of the sac tissue. Excellent kinetic data showed that transport was linear up to 75 min and over a wide range of concentrations (0.025 - (10 mM). Mannitol was not detected in the tissue and transport was enhanced by EGTA, confirming the paracellular route of passage. Sacs prepared from colon also showed mannitol transport, but at a slower rate. Comparisons with Caco-2 cell monolayers showed that the everted sacs exhibited higher levels of paracellular transport than the cultured cell line. The improved everted gut sac system is an inexpensive and relatively simple technique with considerable potential as an in vitro tool to study the mechanisms, kinetics and enhancement of drug absorption across the small intestine at different sites and in the colon. PMID: 9725499 [PubMed - indexed for MEDLINE]
Everted rat intestinal sacs: a new model for the quantitation of P-glycoprotein mediated-efflux of anticancer agents. Carreno-Gomez B, Duncan R. Centre for Polymer Therapeutics, School of Pharmacy, University of London, U.K. P-Glycoprotein (p-gp) situated in the epithelium of the gastrointestinal tract is a recognised barrier limiting oral absorption of antitumour agents. Here we describe the rat everted gut sac as a new in vitro model for quantitation of p-gp-mediated efflux of anti-cancer agents using [3H]vinblastine, [14C] doxorubicin and verapamil as reference compounds. Tissue and serosal uptake of [3H]vinblastine was linear over 90 min (0.031 +/- 0.001 and 0.003 +/- 0.001 ng/mg protein/h respectively). [14C]Doxorubicin tissue accumulation was significantly lower; 0.006 +/- 0.001 ng/mg protein/h (p < 0.05) whereas serosal transfer was significantly higher 0.017 +/- 0.001 ng/mg protein/h (p < 0.05) than [3H]vinblastine. Addition of verapamil (40 ng/mL) increased significantly both tissue accumulation of [3H] vinblastine and [14C]doxorubicin (to 0.060 +/- 0.024 and 0.034 +/- 0.012 ng/mg protein/h respectively) and serosal transfer (to 0.006 +/- 0.002 and 0.023 +/- 0.001 ng/mg protein/h) (p < 0.05 in all cases). The reproducibility of this in vitro model suggests that the rat everted gut sac is a useful screening tool for studying transport of p-gp substrates and potential p-gp modifiers. PMID: 11062737 [PubMed - indexed for MEDLINE]
The roles of P-glycoprotein and intracellular metabolism in the intestinal absorption of methadone: in vitro studies using the rat everted intestinal sac. Bouer R, Barthe L, Philibert C, Tournaire C, Woodley J, Houin G. Laboratoire de Cinetique des Xenobiotiques, Faculte des Sciences Pharmaceutiques, Toulouse, France. Methadone is used as a treatment for opiate detoxification in methadone maintenance programs. Intra- and inter-patient variations in methadone bioavailability have been observed after oral methadone treatment and this makes it difficult to predict a dosing regimen. Intestinal absorption and metabolism could explain these variations. The in vitro gut sac model was used to study the intestinal absorption of methadone, and it confirmed that methadone is a substrate for P-glycoprotein. The transport of methadone was increased in presence of P-gp inhibitors verapamil and quinidine. The appearance of a major metabolite of methadone, 2-ethylidene-1, 5-dimethyl-3, 3-diphenyl pyrrolidine (EDDP) in the gut sac contents also demonstrated the existence of intestinal metabolism of methadone. PMID: 10456292 [PubMed - indexed for MEDLINE]
 The absorption behavior of cyclosporin A lecithin vesicles in rat intestinal tissue. Chen Y, Ping Q, Guo J, Lv W, Gao J. Department of Pharmaceutics, China Pharmaceutical University, 21009, Nanjing, PR China. The purpose of the study was to investigate the absorption behavior of lecithin vesicles of cyclosporin A (CsA-VES), prepared by the rotary evaporation method and treated further with sonication. The everted gut sac technique and in situ circulation method were used to examine: (1) relationship between the CsA-VES absorption velocity and the CsA-VES content; (2) the influence of the intestinal mucus, blank vesicles, concentration of Na(+), energy inhibitor and P-gp inhibitor on the absorption of CsA-VES; and (3) the respective accumulated content of CsA in the incubating medium and the sacs after incubation with Sandimmum Neoral((R))(CsA-NEO) and CsA-VES. Our results showed there was a saturated absorption of CsA. Most CsA-VES accumulated in the mucus before it reached the intestinal tissue. There was no significant difference in the accumulated absorption content in the incubating medium and the sacs of CsA-NEO and CsA-VES. The addition of blank vesicles and concentration of Na(+) had no significant influence on the accumulated absorption of CsA (P>0.05).The energy inhibitor and P-gp inhibitor influenced the accumulated absorption of CsA significantly (P<0.05). CsA-VES may be transported by phagocytosis. Mucus was a barrier blocking the diffusion of CsA-VES. CsA-NEO and CsA-VES showed equal absorption levels in the intestine. PMID: 12878392 [PubMed - in process]
 Evaluation of anhydride oligomers within polymer microsphere blends and their impact on bioadhesion and drug delivery in vitro. Santos CA, Freedman BD, Ghosn S, Jacob JS, Scarpulla M, Mathiowitz E. Spherics, Inc., Lincoln, RI 02865, USA. The effect of the addition of small molecular weight anhydride oligomers to polymer microspheres was evaluated and increased bioadhesion of the composite was demonstrated. Blends of low molecular weight anhydride oligomers with thermoplastic poly(fumaric-co-sebacic anhydride) [p(FASA)] and polycaprolactone were examined. The effects of anhydride oligomers on polymer microsphere degradation, crystallinity, and surface morphology were also explored. The results demonstrated that fumaric anhydride oligomer remained within polymer microspheres for several hours after exposure to phosphate buffer, formed a homogenous crystalline blend, increased bioadhesion as measured on rat intestine, and enhanced drug delivery in vitro as measured by the everted sac technique. PMID: 12809786 [PubMed - in process]
 Absorption of quercetin-3-glucoside and quercetin-4'-glucoside in the rat small intestine: the role of lactase phlorizin hydrolase and the sodium-dependent glucose transporter. Day AJ, Gee JM, DuPont MS, Johnson IT, Williamson G. Procter Department of Food Science, University of Leeds, Leeds LS2 9JT, UK. a.j.day@food.leeds.ac.uk Two hypotheses on absorption mechanisms of flavonoid glucosides across the small intestine have been proposed: active uptake of the quercetin glucoside by the sodium-dependent glucose transporter (SGLT1) with subsequent deglycosylation within the enterocyte by cytosolic beta-glucosidase, or luminal hydrolysis of the glucoside by lactase phlorizin hydrolase (LPH) and absorption by passive diffusion of the released aglycone. To test the above hypotheses we employed phlorizin (as an inhibitor of SGLT1) and N-(n-butyl)-deoxygalactonojirimycin (as an inhibitor of the lactase domain of LPH) in a rat everted-jejunal sac model. Quercetin-4'-glucoside mucosal hydrolysis was 10 times greater than quercetin-3-glucoside hydrolysis in the absence of inhibitors (449 and 47 nmol g(-1) tissue, respectively), despite the similar amounts (13+/-4 and 9+/-1 nmol g(-1), respectively) being transferred to the serosal compartment during the 15 min incubation. Apical hydrolysis of both quercetin glucosides was significantly reduced in the presence of NB-DGJ (80%), and transfer of quercetin (measured as quercetin metabolites) to the serosal solution was also significantly reduced (40-50%). In the presence of phlorizin, transfer of metabolites to the serosal solution was only reduced in the case of quercetin-4'-glucoside. Evidently the mechanism of absorption of quercetin-4'-glucoside involves both an interaction with SGLT1 and luminal hydrolysis by LPH, whereas quercetin-3-glucoside appears to be absorbed only following hydrolysis by LPH. PMID: 12663055 [PubMed - indexed for MEDLINE]
Effect of polyoxyl 35 castor oil and Polysorbate 80 on the intestinal absorption of digoxin in vitro. Cornaire G, Woodley JF, Saivin S, Legendre JY, Decourt S, Cloarec A, Houin G. Laboratoire de Cinetique des Xenobiotiques, Faculte des Sciences Pharmaceutiques, Toulouse, France. Surfactants are classically used to improve the solubilization of lipophilic drugs such as digoxin. Polysorbate 80 and Cremophor EL (polyoxyl 35 castor oil) are such surfactants but they may also modulate the action of P-glycoprotein, an energy-dependent "counter-transport" system implicated in the phenomenon of multidrug resistance in cancer cells. P-glycoprotein is also present in the intestine on the apical membrane of mature enterocytes and can potentially reduce the absorption of a wide range of drugs. In this study, using the improved everted gut sac method, the effects of Polysorbate 80, Cremophor EL and cyclosporin on the absorption of digoxin were studied. An increase in the uptake of digoxin in the presence of these three products could be shown with our in vitro model. Cremophor EL and Polysorbate 80 had no toxic effects at the concentrations used. These results suggest that surfactants such as Cremophor EL and Polysorbate 80 should not only support solubilization but can also modulate the P-glycoprotein system to improve the bioavailability of poorly absorbed drugs. PMID: 10918954 [PubMed - indexed for MEDLINE]
Liquid chromatographic-mass
spectrometric method to assess cytochrome P450-mediated metabolism of
testosterone by rat everted gut sacs.
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