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  • 1
    Electronic Resource
    Electronic Resource
    Comparison of the Permeability Characteristics of a Human Colonic Epithelial (Caco-2) Cell Line to Colon of Rabbit, Monkey, and Dog Intestine and Human Drug Absorption (1993)
    Springer
    Pharmaceutical research 10 (1993), S. 113-118 
    Details
    ISSN: 1573-904X
    Keywords: permeability coefficient ; Caco-2 ; dog, monkey, and rabbit intestinal segments ; human absorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The in vitro permeabilities of Caco-2 monolayers and permeabilities in tissue sections from colon of monkey, rabbit, and dog were compared using a series of compounds. The selected compounds differed in their physicochemical properties, such as octanol/water partition coefficient, water solubility, and molecular weight. Their structure included steroids, carboxylic acids, xanthins, alcohols, and polyethylene glycols. A linear permeability relationship was established between Caco-2 and colon tissue from both rabbit and monkey. The results suggest that Caco-2 is twice as permeable as rabbit and five times as permeable as monkey colon. However, no clear relationship could be established between Caco-2 monolayers and dog colon permeability. A relationship between permeability in Caco-2 monolayers and human absorption was found. The results suggest that within certain limits, permeability of Caco-2 monolayers may be used as a predictive tool to estimate human drug absorption.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018937416447
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    In Vitro Measurement of Gastrointestinal Tissue Permeability Using a New Diffusion Cell (1988)
    Springer
    Pharmaceutical research 5 (1988), S. 372-376 
    Details
    ISSN: 1573-904X
    Keywords: In vitro apparatus ; diffusion cell ; intestinal permeability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A new diffusion cell, derived from the Ussing chamber, was developed for the measurement of tissue permeability. This cell incorporates the attributes of using a single material and laminar flow across the tissue surface. In addition, the design allows the cell to be manufactured in a wide range of sizes to allow optimization of surface area to volume for a variety of tissues. The apparatus is applicable to the evaluation of transport of compounds through mucosal/epithelial barriers, i.e., gastrointestinal tissue. Active transport, permeability enhancers, enzymatic degradation, and absorption in various tissue sections can be explored. Preliminary data are consistent with the expected effects of molecular size and partition coefficient of a transported molecule on permeability in epithelial tissue. In addition, active transport of D-glucose and inhibition by phloridzin and ouabain can be demonstrated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1015911712079
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  • 3
    Electronic Resource
    Electronic Resource
    A Correlation of Permeabilities for Passively Transported Compounds in Monkey and Rabbit Jejunum (1989)
    Springer
    Pharmaceutical research 6 (1989), S. 857-862 
    Details
    ISSN: 1573-904X
    Keywords: in vitro permeability study ; rabbit ; monkey ; intestine ; species correlation ; passive transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Permeability measurements were conducted for a series of compounds using in vitro tissue sections from monkey and rabbit jejunum. Jejunal segments were stripped of serosal musculature and mounted in a diffusion-cell system, using previously described methods and equipment. Permeability determinations of radiolabeled compounds ranging over two orders of magnitude in molecular weight were conducted. For the compounds examined, the permeability of the rabbit jejunum was approximately twice that of the monkey. This was in contrast to the relationship implied by the stripped tissue thickness measurements of 0.92 and 0.83 mm for rabbit and monkey, respectively. An investigation of the size of the paracellular space in the jejunum was undertaken to account for this apparent discrepancy in tissue permeability. Scanning electron micrographs of intestinal sections revealed a similar packing density of cells between species; however, a difference was noted in the shape and number of villi per unit area. Comparative measurements of the paracellular volume in both species using mannitol and methoxyinulin as extracellular space markers further suggests that the paracellular junctions are similar in size but more numerous per unit area of rabbit jejunum than that of the monkey. In contrast to passively transported compounds, the active transport of D-glucose was greater in monkey jejunum compared to rabbit tissue segments. When active transport was inhibited by blockade of the sodium pump with ouabain, the passive component of D-glucose transport for both rabbit and monkey tissue was in agreement with the relationship demonstrated above for compounds which are solely transported by passive processes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1015956421281
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Evidence for Site-Specific Absorption of a Novel ACE Inhibitor (1989)
    Springer
    Pharmaceutical research 6 (1989), S. 759-765 
    Details
    ISSN: 1573-904X
    Keywords: site-specific absorption ; moexipril ; Stella ; pharmacokinetic modeling ; ACE inhibitor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Moexipril {2-[(l-ethoxycarbonyl)-3-phenylpropyl]amino-l-oxopropyl]-6,7-dimethoxy-1,2,3,4-tetra-hydroisoquinoline-3-carboxylic acid (S,S,S)}, an ester prodrug of an ACE inhibitor, was formulated in controlled-release preparations with a range of in vitro release rates, to provide a prolonged input of drug in vivo. However, pharmacokinetic studies with the controlled-release dosage forms in humans produced plasma profiles with the same characteristics and time to peak as an immediate-release capsule. In vitro dissolution data from the controlled-release dosage form, as well as the known characteristics of the polymer used to control drug release from the dosage form, suggest no reason to suspect an abrupt halt to the in vivo release of the drug after 1–2 hr. The lack of sustained blood levels is, therefore, most likely due to failure of the GI tract to absorb the drug beyond some location in the upper small intestine, i.e., site-specific absorption. This theory is supported by a series of computer simulations involving moexipril and the active moiety, moexipril diacid. Possible mechanisms include poor drug permeability, a pH effect whereby the zwitterionic form of the drug is more rapidly absorbed, and esterase cleavage of moexipril to the poorly absorbed moexipril diacid.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1015919413103
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Characterization of the Unstirred Water Layer in Caco-2 Cell Monolayers Using a Novel Diffusion Apparatus (1991)
    Springer
    Pharmaceutical research 8 (1991), S. 222-227 
    Details
    ISSN: 1573-904X
    Keywords: Caco-2 ; unstirred water layer ; intestinal permeability ; steroids ; cell culture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Caco-2 monolayers grown on Transwell polycarbonate membranes have been characterized as a valuable tool in drug transport studies. Despite the clear advantages of this system, the lack of stirring may create an unstirred water layer (UWL) whose resistance may limit the transcellular transport of lipophilic molecules. The objective of this study was to evaluate a novel diffusion cell where the transport buffer is mixed by gas lift and to determine the mixing flow rate needed to reduce the thickness (h) of the UWL adjacent to cell monolayers. The transport of the leakage marker, mannitol, remained at least 15-fold lower than the flux of testosterone, indicating that the stirring flow rates used did not affect the integrity of the monolayers. The permeability (P) of testosterone (log PC 3.13) across monolayers mounted on this diffusion cell was 4.07, 10.90, and 14.18 × 10−5 cm/sec at flow rates of 0, 15, and 40 ml/min, respectively, and the apparent UWLs were calculated to be 1966, 733, and 564µm. P and h in the stagnant Transwell were 3.08 × 10−5 cm/sec and 2597 µm, respectively. On the other hand, h was significantly smaller in the unstirred, cell-free membranes than in their cell-containing counterparts. P was correlated with lipophilicity and, in the case of the more lipophilic compounds, with the mixing flow rate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1015848205447
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Permeability Characteristics of Various Intestinal Regions of Rabbit, Dog, and Monkey (1992)
    Springer
    Pharmaceutical research 9 (1992), S. 1580-1586 
    Details
    ISSN: 1573-904X
    Keywords: intestinal permeability ; partition coefficient ; jejunum ; colon ; species differences
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The in vitro permeability of a series of both hydrophilic and lipophilic compounds, as defined by the octanol/water partition coefficient, was measured in four segments of rabbit, monkey, and dog intestine using a side-by-side diffusion cell. A linear relationship was established for tissue resistance to hydrophilic compound diffusion in jejunum and colon among rabbit, monkey, and dog. The results suggest that rabbit jejunum is twice as permeable as monkey and dog jejunum. The colonic tissues of monkey, rabbit, and dog demonstrate similar permeabilities. Measuring the permeabilities of different tissues with compounds of similar physicochemical properties allows comparison of tissue restriction to transport. Thus, in vitro permeability measurements may be used to investigate physiological differences of various intestinal tissue segments that influence tissue permeability. Investigating the permeability of different intestinal segments from various species could allow the identification of an appropriate in vitro intestinal permeability model that will lead to the prediction of intestinal absorption in humans, eliminating the need for extensive and often misleading in vivo animal testing.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1015812408231
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    Paper (German National Licenses)
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