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  • 1
    Electronic Resource
    Electronic Resource
    Renin Inhibitor: Transport Mechanism in Rat Small Intestinal Brush-Border Membrane Vesicles (1994)
    Springer
    Pharmaceutical research 11 (1994), S. 1448-1451 
    Details
    ISSN: 1573-904X
    Keywords: renin inhibitor ; rat intestinal brush-border membrane vesicle ; BBMV ; proton coupled uphill transport ; peptide carrier system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The transport characteristics of the renin inhibitor ((3S,4S)-4-[N-morpholinoacetyl-(l-naphthyl)-L-alanyl-N-methyl-(4-thiazolyl)-L-alanyl]amino-3-hydroxy-5-cyclohexyl-l-(4-pyridyl)-l-pentanone; CH3-18) in rat small intestinal brush-border membrane vesicles (BBMV) were examined by a rapid filtration technique. The uptake of CH3-18 was markedly stimulated by an inwardly directed H+ gradient (pH 7.5 inside, pH 5.5 outside) and showed an uphill transport. It was competitively inhibited by tripeptides and tetrapeptides, but not by amino acids or dipeptides. A countertransport effect on the uptake of CH3-18 was observed in the vesicle preloaded with a tripeptide. Effects of the fragments of several renin inhibitors were evaluated by their inhibitory and countertransport effects on the uptake of CH3-18. The morpholino group at the N-terminal was found to be important for the uptake of CH3-18.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018900124257
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  • 2
    Electronic Resource
    Electronic Resource
    Characteristics of Ceftibuten Uptake into Caco-2 Cells (1994)
    Springer
    Pharmaceutical research 11 (1994), S. 1761-1765 
    Details
    ISSN: 1573-904X
    Keywords: ceftibuten ; Caco-2 ; uptake ; brush-border membrane vesicles ; oligopeptide ; oral cephem
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The characteristics of ceftibuten uptake into Caco-2 cells grown in a collagen-coated dish were examined. Ceftibuten showed stereoselective and pH-dependent uptake. The pH-dependency of ceftibuten was more marked than that of cefaclor or cephalexin, but all three antibiotics showed maximal uptake at pH 5.5. Ceftibuten uptake was linear for the initial 1 hr and then reached a plateau. The initial uptake (15 min) was markedly reduced by the addition of 2,4-dinitrophenol or FCCP (a protonophore), or by lowering the incubation temperature. The uptake of ceftibuten into the brush-border membrane vesicles prepared from cultured Caco-2 cells showed an overshoot in the presence of an H+-gradient. These findings indicated that the uptake of ceftibuten was energy-dependent, especially H+-gradient-dependent. Uptake inhibition by various compounds was compared using Caco-2 cells. Amino acids and a tetrapeptide did not inhibit uptake, whereas di- or tri-peptides were effective inhibitors. These observations suggest that ceftibuten is taken up by a carrier-mediated transport system(s) for dipeptides. Various antibiotics differed in their ability to inhibit uptake, with cyclacillin showing maximum inhibition. Differences in the inhibitory effect may be accounted for by the heterogeneity (multiplicity) of the transport systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018919517839
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  • 3
    Electronic Resource
    Electronic Resource
    Transport Characteristics of S-1090, A New Oral Cephem, in Rat Intestinal Brush-Border Membrane Vesicles (1995)
    Springer
    Pharmaceutical research 12 (1995), S. 1488-1492 
    Details
    ISSN: 1573-904X
    Keywords: S-1090 ; transport ; brush-border membrane ; oligopeptide ; histidine ; oral cephem
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. Elucidating the transport characteristics of S-1090, a new orally active cephalosporin in rat small intestinal brush-border membranes. Methods. A rapid filtration technique. Results. The uptake of S-1090 was stimulated by an inwardly directed H+-gradient, but did not show overshooting uptake. To investigate the transport system, the inhibitory and countertransport effects of various compounds on S-1090 uptake were examined. Although the dipeptides and tripeptides composed of amino acids with aliphatic side chains did not inhibit the uptake of S-1090, those having histidine, proline or tryptophan as the N-terminal amino acid showed an inhibitory effect. Among the oral cephems tested, ceftibuten showed marked inhibition, while cefaclor and cephalexin had no inhibitory effect. Countertransport effects on S-1090 uptake were observed only when the vesicles were preloaded with histidyl peptides such as His-Gly or His-Ala, while other compounds which exhibited inhibition had no countertransport effect. Conclusions. Based on the above results, there seems to be heterogeneity (multiplicity) in the oligopeptide transport system which may depend on the structure of the N-terminal amino acid. S-1090 may be dominantly transported via a system that recognizes peptides having histidine as the N-terminal amino acid.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1016287421436
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  • 4
    Electronic Resource
    Electronic Resource
    Transport Characteristics of Ceftibuten (7432-S), a New Oral Cephem, in Rat Intestinal Brush-Border Membrane Vesicles: Proton-Coupled and Stereoselective Transport of Ceftibuten (1989)
    Springer
    Pharmaceutical research 6 (1989), S. 302-307 
    Details
    ISSN: 1573-904X
    Keywords: ceftibuten ; proton-coupled uphill transport ; rat intestinal brush-border membrane vesicles ; stereoselective transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The transport characteristics of ceftibuten in rat intestinal brush-border membrane vesicles were investigated by a rapid filtration technique. Ceftibuten uptake was markedly stimulated by an inwardly directed H+ gradient (pH 7.5 inside, pH 5.5 outside) in comparison with that in the absence of a H+ gradient. The uptake at 30 sec was four times greater than that observed at equilibrium (overshoot phenomenon), while the H+ gradient-stimulated uptake of ceftibuten was markedly reduced in the presence of FCCP, a protonophore. These results suggested H+-coupled uphill transport of ceftibuten. In contrast, an inwardly directed Na+ gradient had no effect on ceftibuten uptake. The valinomycin-induced K+ diffusion potential (inside positive) significantly stimulated the ceftibuten uptake, suggesting net transfer of the negative charge. In contrast to the cis-isomer ceftibuten, the trans isomer of ceftibuten is not readily absorbed from the intestine, and its uptake was found not to be affected by a H+ gradient. Since the lipophilicity of the trans isomer is similar to that of ceftibuten, the uptake process appears to be stereoselective. The initial uptake of ceftibuten and its analogue cefaclor was concentration dependent under a H+ gradient. The apparent K m value was 0.2 mM for ceftibuten and 3.0 mM for cefaclor.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1015994323639
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Transport Characteristics of Ceftibuten, a New Oral Cephem, in Rat Intestinal Brush-Border Membrane Vesicles: Relationship to Oligopeptide and Amino β-Lactam Transport (1989)
    Springer
    Pharmaceutical research 6 (1989), S. 308-312 
    Details
    ISSN: 1573-904X
    Keywords: ceftibuten ; transport ; brush-border membrane ; oligopeptide ; amino β-lactam ; oral cephem
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Ceftibuten undergoes H+-coupled uphill transport across rat small intestinal brush-border membrane vesicles. The effects of amino acids, peptides, folate, and β-lactams on the uptake of ceftibuten were examined. Uptake of ceftibuten was competitively inhibited by dipeptides or tripeptides. A counter-transport effect on ceftibuten uptake was observed in the vesicle preloaded with these peptides, and the transport was temporarily against a concentration gradient (overshooting). On the other hand, ceftibuten uptake was not changed by amino acids and a tetrapeptide. Therefore, ceftibuten is predominantly transported via the oligopeptide transport system in the brush-border membranes. The relationship of ceftibuten transport to folate and other oral antibiotics was also investigated. Cyclacillin, cephradine, and cefadroxil exhibited both inhibitory and countertransport effects, but folate, cefaclor, and cephalexin showed only a slight inhibitory effect. As the transport of cefaclor showed no uphill uptake in the presence of a H+ gradient and its H+ stimulated uptake was small, a H+ gradient-independent carrier-mediated system seems to participate in its transport. These findings suggest that two different carrier-mediated transport systems, H+ gradient dependent and independent, may exist for oral cephems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1015946407709
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    Paper (German National Licenses)
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