Mechanisms of Cefadroxil Uptake in the Choroid Plexus: Studies in Wild-Type and PEPT2 Knockout Mice
| Autor: | David Smith, Hong Shen, Jianming Xiang, Yongjun Hu, Richard F. Keep, Scott M. Ocheltree |
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| Rok vydání: | 2003 |
| Předmět: |
Time Factors
Organic anion transporter 1 Stereochemistry Biological Transport Active Peptide Mice Cerebrospinal fluid medicine Animals Mice Knockout Pharmacology chemistry.chemical_classification Dose-Response Relationship Drug Symporters biology Cefadroxil Temperature Wild type Transporter Hydrogen-Ion Concentration Molecular biology Anti-Bacterial Agents chemistry Choroid Plexus Knockout mouse biology.protein Molecular Medicine Choroid plexus medicine.drug |
| Zdroj: | Journal of Pharmacology and Experimental Therapeutics. 308:462-467 |
| ISSN: | 1521-0103 0022-3565 |
| DOI: | 10.1124/jpet.103.060400 |
| Popis: | The choroid plexus uptake of [(3)H]cefadroxil was studied in peptide transporter 2 (PEPT2) wild-type and null mice as a function of temperature, transport inhibitors, pH, and saturability. At normal pH (7.4) and temperature (37 degrees C), the uptake of 1 microM cefadroxil was reduced by 83% in PEPT2(-/-) mice as compared with PEPT2(+/+) mice (p0.001). A further reduction was achieved in null animals by reducing the temperature to 4 degrees C, or by adding saturating concentrations of unlabeled cefadroxil or p-aminohippurate (p0.05). Glycylsarcosine coadministration could inhibit the uptake of cefadroxil in PEPT2(+/+) mice (p0.01) but not PEPT2(-/-) mice. Although a proton-stimulated uptake of cefadroxil was demonstrated in PEPT2(+/+) mice (pH 6.5 versus pH 7.4; p0.01), no pH dependence was observed in PEPT2(-/-) mice. Kinetic parameters for cefadroxil (without p-aminohippurate) in wild-type mice were: V(max) = 5.4 pmol/mg/min, K(m) = 34 microM, and K(d) = 0.0069 microl/mg/min; in the presence of p-aminohippurate, the parameters were: V(max) = 4.1 pmol/mg/min, K(m) = 27 microM, and K(d) = 0.0064 microl/mg/min. In null animals, the kinetic parameters of cefadroxil (without p-aminohippurate) were: V(max) = 2.7 pmol/mg/min, K(m) = 110 microM, and K(d) = 0.0084 microl/mg/min; in the presence of p-aminohippurate, only a K(d) = 0.010 microl/mg/min was observed. Based on kinetic and inhibitor analyses, it was determined that (under linear conditions), 80 to 85% of cefadroxil's uptake in choroid plexus is mediated by PEPT2, 10 to 15% by organic anion transporter(s), and 5% by nonspecific mechanisms. These findings demonstrate that PEPT2 is the primary transporter responsible for cefadroxil uptake in the choroid plexus. Moreover, the data suggest a role for PEPT2 in the clearance of peptidomimetics from cerebrospinal fluid. |
| Databáze: | OpenAIRE |
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