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  • 1
    Electronic Resource
    Electronic Resource
    In Vivo and in Vitro Analysis of Skin Penetration Enhancement Based on a Two-Layer Diffusion Model with Polar and Nonpolar Routes in the Stratum Corneum (1994)
    Springer
    Pharmaceutical research 11 (1994), S. 185-191 
    Details
    ISSN: 1573-904X
    Keywords: in vitro skin penetration ; in vivo skin penetration ; penetration enhancement ; 1-geranylazacycloheptan-2-one ; diffusion model ; urinary excretion ; deconvolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract In vitro and in vivo skin penetration of three drugs with different lipophilicities and the enhancing effects of l-geranylazacycloheptan-2-one (GACH) were studied in rats. In vivo drug absorption profiles obtained by deconvolution of urinary excretion profiles were compared to the corresponding in vitro data obtained with a diffusion experiment. In vivo skin penetration of lipophilic butylparaben was considerably greater than that observed in vitro, while hydrophilic mannitol and acyclovir showed low penetration in both systems without GACH pretreatment. On the other hand, GACH enhanced mannitol and acyclovir penetration, especially in the in vivo system. Analysis of absorption profiles, using a two-layer skin model with polar and nonpolar routes in the stratum corneum, suggested that the diffusion length of a viable layer (viable epidermis and dermis) was shorter in vivo than in vitro and the effective area of the polar route in the stratum corneum was larger in vitro without GACH pretreatment. GACH increased the partitioning of acyclovir into the nonpolar route to the same extent in both systems. In addition, GACH increased the effective area of the polar route in vivo, probably because of enhanced water permeability; however, this effect was smaller in vitro since the stratum corneum was already hydrated even without GACH pretreatment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018986803958
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  • 2
    Electronic Resource
    Electronic Resource
    Organic Cation Transport in Rabbit Alveolar Epithelial Cell Monolayers (1999)
    Springer
    Pharmaceutical research 16 (1999), S. 1280-1287 
    Details
    ISSN: 1573-904X
    Keywords: alveolar epithelial cell monolayers ; organic cation transport ; guanidine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. To characterize organic cation (OC) transport in primary cultured rabbit alveolar epithelial cell monolayers, using [l4C]-guanidine as a model substrate. Methods. Type II alveolar epithelial cells from the rabbit lung were isolated by elastase digestion and cultured on permeable filters pre-coated with fibronectin and collagen. Uptake and transport studies of [14C]-guanidine were conducted in cell monolayers of 5 to 6 days in culture. Results. The cultured alveolar epithelial cell monolayers exhibited the characteristics of a tight barrier. [14C]-Guanidine uptake was temperature dependent, saturable, and inhibited by OC compounds such as amiloride, cimetidine, clonidine, procainamide, propranolol, tetraethyl-ammonium, and verapamil. Apical guanidine uptake (Km = 129 ± 41 μM, Vmax = 718 ± 72 pmol/mg protein/5 min) was kinetically different from basolateral uptake (Km = 580 ± 125 (μM, Vmax = 1,600 ± 160 pmol/mg protein/5 min). [14C]-Guanidine transport across the alveolar epithelial cell monolayer in the apical to basolateral direction revealed a permeability coefficient (Papp) of (7.3 ± 0.4) × 10-7 cm/sec, about seven times higher than that for the paracellular marker [14C]-mannitol. Conclusions. Our findings are consistent with the existence of carrier-mediated OC transport in cultured rabbit alveolar epithelial cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1014814017316
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  • 3
    Electronic Resource
    Electronic Resource
    Pharmacokinetic Analysis of Drug Disposition After Intratumoral Injection in a Tissue-Isolated Tumor Perfusion System (1996)
    Springer
    Pharmaceutical research 13 (1996), S. 1438-1444 
    Details
    ISSN: 1573-904X
    Keywords: pharmacokinetics ; tissue-isolated tumor ; intratumoral injection ; drug disposition ; perfusion experiment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. The purpose of this study was to establish an experimental system for evaluation of the intratumoral behavior of drugs after intratumoral injection using perfused tissue-isolated tumor preparations of Walker 256 carcinoma (3.46–9.73g, n = 16). Methods. We quantified the recovery of Phenol Red (model drug) in the tumor, leakage from the tumor surface and the venous outflow after intratumoral injection using perfused tissue-isolated tumors, and analyzed venous appearance curves based on a pharmacokinetic model in which the tumor tissue was assumed to be divided into two compartments, i.e., well- and poorly-perfused regions. Results. In small tumors (Type 1, 5.42 ± 0.39 g), the drug appeared immediately in the venous outflow, and the amount remaining in the tumor tissue at 2 hr after injection was small. In contrast, the venous appearance rate reached a significantly lower peak a few minutes after injection, and a large amount of injected drug remained in some large tumors (Type 2, 8.17 ± 0.51 g). Pharmacokinetic analysis revealed that there was a correlation between tumor weight and the rate constants of transfer from the poorly-perfused region to the well-perfused region, and between the rate constants of transfer from the well-perfused region to the venous outflow and dosing ratios into the well-perfused region. Conclusions. An experimental system and analytical method were established for the evaluation of the intratumoral behavior of drugs after intratumoral injection using a tissue-isolated tumor perfusion system. This experimental system will be useful in analyzing the antitumor drug disposition after intratumoral injection.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1016054807555
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  • 4
    Electronic Resource
    Electronic Resource
    Effect of Particle Size and Charge on the Disposition of Lipid Carriers After Intratumoral Injection into Tissue-isolated Tumors (1998)
    Springer
    Pharmaceutical research 15 (1998), S. 128-132 
    Details
    ISSN: 1573-904X
    Keywords: pharmacokinetics ; tissue-isolated tumor ; liposome ; emulsion ; intratumoral injection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. Pharmacokinetic properties of various lipid carriers (liposome and emulsions) after intratumoral injection were studied in perfusion experiments using tissue-isolated tumor preparations of Walker 256 carcinosarcoma. Methods. Four types of lipid carriers, large emulsion (254 nm), small emulsion (85 nm), neutral liposomes (120 nm) and cationic liposomes (125 nm) were prepared. We quantified their recovery from the tumor, leakage from the tumor surface and venous outflow after intratumoral injection into perfused tissue-isolated tumors, and analyzed venous appearance curves based on a pharmacokinetic model. Results. In contrast to the small emulsion and neutral liposomes, which immediately appeared in the venous outflow perfusate following intratumoral injection, the appearance of the cationic liposomes and the large emulsion was highly restricted, clearly demonstrating that intratumoral clearance of these formulations can be greatly retarded by the cationic charge and large particle size, respectively. The venous appearance rate-time profiles were fitted to equations derived from a two-compartment model by nonlinear regression analysis. When the calculated parameters were compared among these four formulations, the venous appearance rate did not exhibit such a large difference; however, the rate of transfer from the injected site to the compartment which involves clearance by venous outflow was all very different. Conclusions. The results of this study indicate that the determining factor which alters the pharmacokinetic properties of these lipid carriers after intratumoral injection is not the rate of transfer from the interstitial space to the vascular side but the rate of intratumoral transfer from the injection site to the well-vascularized region.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1011921324952
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  • 5
    Electronic Resource
    Electronic Resource
    In Vivo Evaluation of Acyclovir Prodrug Penetration and Metabolism Through Rat Skin Using a Diffusion/Bioconversion Model (1997)
    Springer
    Pharmaceutical research 14 (1997), S. 56-62 
    Details
    ISSN: 1573-904X
    Keywords: in vivo skin penetration ; acyclovir prodrug ; diffusion/ bioconversion model ; deconvolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. In order to evaluate the in vivo penetration of prodrugs which undergo metabolism in skin, we analyzed thein vivo penetration profiles of acyclovir prodrugs based on a two-layer skin diffusion model in consideration of metabolic process. Methods. Acyclovir prodrugs (e.g., valerate, isovalerate and pivarate) were used as model prodrugs and the amounts excreted in urine were measured after percutaneous application. In vivo penetration profiles were then estimated by employing a deconvolution method and the penetration of acyclovir prodrugs was analyzed using a diffusion model. Subsequently, diffusion, partitioning and metabolic parameters were compared under in vitro and in vivo conditions. Results. Although total penetration amounts at the end of the experiment were similar for the three prodrugs, the ratio of intact prodrug to total penetration amount differed significantly. Moreover, the excretion and absorption profiles were also very different for each prodrug. Enzymatic hydrolysis rate constants calculated under in vivo conditions were considerably larger than those obtained in the skin homogenate and in vitro penetration experiments. Conclusions. The present skin diffusion/bioconversion model combined with computer analysis enables us to comprehensively account for diffusion, partitioning and metabolism during in vivo percutaneous absorption. Nevertheless, different enzymatic hydrolysis rate constants obtained under bothin vivo and in vitro conditions demonstrate the difficulty of obtaining accurate values for in vivo enzymatic activity from related in vitro experiments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1012003416968
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  • 6
    Electronic Resource
    Electronic Resource
    Gly-L-Phe Transport and Metabolism Across Primary Cultured Rabbit Tracheal Epithelial Cell Monolayers (1997)
    Springer
    Pharmaceutical research 14 (1997), S. 238-240 
    Details
    ISSN: 1573-904X
    Keywords: tracheal epithelial cell monolayer ; transport ; metabolism ; Gly-L-Phe ; rabbit ; aminopeptidase M
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1012017214668
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  • 7
    Electronic Resource
    Electronic Resource
    Characterization of Plasmid DNA Binding and Uptake by Peritoneal Macrophages from Class A Scavenger Receptor Knockout Mice (1999)
    Springer
    Pharmaceutical research 16 (1999), S. 503-508 
    Details
    ISSN: 1573-904X
    Keywords: scavenger receptors ; knockout mice ; peritoneal macrophages ; plasmid DNA ; receptor-mediated endocytosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. Plasmid DNA (pDNA) has become an important class of macromolecular agent suitable for non-viral gene therapy as well as DNA vaccination. Our recent study has suggested that pDNA is taken up by mouse peritoneal macrophages via a specific mechanism mediated by a receptor similar to the scavenger receptor (SR). This study was designed to further characterize the pDN A uptake by macrophages in order to elucidate the mechanism. Methods. The binding and uptake of pDNA labeled with 32P or a fluorescent marker were studied in vitro using cultured Chinese hamster ovary (CHO) cells expressing the class A scavenger receptor (SRA) and peritoneal macrophages from SRA-knockout mice. Results. pDNA binding and uptake by CHO(SRA) cells were minimal and almost identical to that by wild-type CHO cells. Macrophages from the knockout mice showed pronounced pDNA binding and uptake as did the control macrophages. In both types of macrophage, pDNA binding was significantly inhibited by cold pDNA, polyinosinic acid and dextran sulfate but not by polycytidylic acid or Ac-LDL. These results provide direct evidence that SRA is not responsible for the significant binding and subsequent uptake of pDNA by mouse peritoneal macrophages. Further binding experiments revealed that, in addition to polyinosinic acid and dextran sulfate, heparin was a potent inhibitor among a variety of polyanionic compounds such as poly-nucleotides, anionic polysaccharides and modified proteins including Ox-LDL. Conclusions. The present study suggest that pDNA binding and uptake by mouse peritoneal macrophages are mediated by a specific mechanism to some defined polyanions not by scavenger receptors. The finding would be an important basis for further studies to elucidate the mechanism(s) of pDNA uptake by macrophages.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018842210588
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  • 8
    Electronic Resource
    Electronic Resource
    Theoretical Design of Prodrug-Enhancer Combination Based on a Skin Diffusion Model: Prediction of Permeation of Acyclovir Prodrugs Treated with l-Geranylazacycloheptan-2-one (1996)
    Springer
    Pharmaceutical research 13 (1996), S. 427-432 
    Details
    ISSN: 1573-904X
    Keywords: prodrug-enhancer combination ; percutaneous absorption ; acyclovir ; l-geranylazacycloheptan-2-one
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. A theoretical design of percutaneous penetration enhancement in which prodrug derivation and enhancer application are combined is proposed based on the skin diffusion model and it is experimentally verified. Methods. Employing acyclovir as a model drug, the hypothesis was tested by synthesis of its prodrugs and evaluation of their in vitro permeation in the rat skin, with or without a penetration enhancer, 1-geranylazacycloheptan-2-one(GACH). Results. Among five acyclovir prodrugs, those with higher lipophilicit-ies (propionate, butyrate, valerate, and hexanoate prodrugs) showed greater skin penetration than those of hydrophilic prodrugs (acetate), when administered in combination with GACH. Furthermore, the observed enhancement ratios were in good agreement with those predicted by theoretical consideration. Conclusions. Thus, skin permeation of prodrugs applied with an enhancer can be predicted and optimized by model analysis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1016000827719
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  • 9
    Electronic Resource
    Electronic Resource
    Comparative Analysis of Percutaneous Absorption Enhancement by d-Limonene and Oleic Acid Based on a Skin Diffusion Model (1994)
    Springer
    Pharmaceutical research 11 (1994), S. 377-383 
    Details
    ISSN: 1573-904X
    Keywords: percutaneous absorption ; percutaneous penetration enhancer ; d-limonene ; oleic acid ; skin diffusion model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Percutaneous absorption-enhancing effects of d-limonene and oleic acid were investigated using three model drugs with different lipophilicities in in vitro diffusion experiments with guinea pig skin. Pretreatment of the skin with d-limonene resulted in a large penetration enhancement for the lipophilic butylparaben (BP) and amphiphilic 6-mercaptopurine (6-MP) but had little effect on the hydrophilic mannitol (MT). Oleic acid caused a large effect only on 6-MP penetration. The penetration profiles were analyzed with a two-layer skin diffusion model consisting of stratum corneum with polar and nonpolar routes and viable epidermis plus dermis. Through curve-fitting, six parameters corresponding to drug diffusivity and partitioning in these three regions of the skin were obtained, and the mechanisms of enhancers were assessed in comparison with those of l-geranylazacycloheptan-2-one (GACH) reported previously. Increased penetration was caused mainly by modification of the barrier property of the nonpolar route in the stratum corneum in all cases. In the nonpolar route, d-limonene increased mainly drug diffusivity, while GACH enhanced predominately drug partitioning. On the other hand, oleic acid moderately increased both parameters.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018904802566
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  • 10
    Electronic Resource
    Electronic Resource
    Dipeptide Uptake and Transport Characteristics in Rabbit Tracheal Epithelial Cell Layers Cultured at an Air Interface (1998)
    Springer
    Pharmaceutical research 15 (1998), S. 979-983 
    Details
    ISSN: 1573-904X
    Keywords: tracheal epithelial cell layer ; transport ; peptide transporter ; carnosine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. To determine the functional presence of a H+/peptide cotransport process in rabbit tracheal epithelial cell layers cultured at an air-interface and its contribution to transepithelial dipeptide transport. Methods. Rabbit tracheocytes were isolated, plated on Transwells, and cultured at an air-interface. After 5 or 6 days in culture, uptake and transepithelial transport of carnosine were examined. Results. Carnosine uptake by tracheocytes was pH-dependent and was saturable with a Michaelis-Menten constant of 170 μM. Moreover, carnosine uptake was inhibited 94% by Gly-L-Phe, 28% by (β-Ala-Gly, but not at all by Gly-D-Phe or by the amino acids β-Ala and L-His. Unexpectedly, transepithelial carnosine transport at pH 7.4 (i.e., in the absence of a transepithelial pH gradient) was similar in both the apical-to-basolateral (ab) and basolateral-to-apical (ba) directions. Lowering the apical fluid pH to 6.5 reduced abtransport 1.6 times without affecting ba transport, consistent with predominantly paracellular diffusion of carnosine under an electrochemical potential gradient. Conclusions. The kinetic behavior of carnosine uptake into cultured tracheal epithelial cell layers is characteristic of a H+-coupled dipeptide transport process known to exist in the small intestine and the kidney. Such a process does not appear to be rate-limiting in the transport of carnosine across the tracheal epithelial barrier.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1011957506181
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