title: Carrier-mediated uptake of grepafloxacin, a fluoroquinolone antibiotic, by the isolated rat lung cells.
abstract: Grepafloxacin (GPFX) is a new quinolone antibiotic (NQ) which is highly distributed to the lung and other tissues. In the present study, to characterize the distribution mechanism of GPFX to the lung, the uptake of GPFX by isolated rat lung cells was examined in vitro. GPFX was rapidly taken up by the cells, and the uptake reached a steady-state within 5 min. The cell-to-medium concentration ratio at equilibrium was 56.8+/-1.9 microL/mg protein, which was much higher than the cellular volume. GPFX uptake consisted of a saturable component (Km: 264+/-181 microM, Vmax: 2.94+/-2.33 nmol/min/mg protein) and a nonsaturable component (Pdif: 7.04+/-2.17 microL/min/mg protein). The uptake of GPFX was reduced in the presence of ATP-depletors (FCCP and Rotenone) and by the replacement of sodium with choline in the medium, suggesting that GPFX uptake is at least partially mediated by an Na+- and energy-dependent process. GPFX uptake tended to be reduced in the presence of other NQs such as levofloxacin, lomefloxacin and sparfloxacin, but was only minimally affected by the substrates of several uptake mechanisms already identified in the liver and kidney such as taurocholate, p-aminohippurate, L-carnitine and tetraethylammonium. These results suggested that GPFX is taken up by the lung partially via carrier-mediated transport system(s), distinct from the identified transporters, and such active transport systems may at least partially account for the efficient distribution of GPFX to the lung.
authors.affiliation: Department of Drug Metabolism, Tokushima Research Institute, Otsuka Pharmaceutical Co., Ltd., Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Sasabe
authors.forename: Yukio
authors.initials: Y
authors.lastname: Kato
authors.forename: Takashi
authors.initials: T
authors.lastname: Suzuki
authors.forename: Minoru
authors.initials: M
authors.lastname: Itose
authors.forename: Gohachiro
authors.initials: G
authors.lastname: Miyamoto
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Sugiyama
mesh_terms: D000255:Adenosine Triphosphate / Q000037:antagonists & inhibitors / Q000378:metabolism; D000465:Algorithms; D000818:Animals; D000900:Anti-Bacterial Agents / Q000378:metabolism*; D001693:Biological Transport, Active; D002352:Carrier Proteins / Q000378:metabolism*; D024841:Fluoroquinolones / Q000378:metabolism*; D007668:Kidney / Q000378:metabolism; D008099:Liver / Q000378:metabolism; D008168:Lung / Q000166:cytology / Q000378:metabolism*; D008297:Male; D010879:Piperazines / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012964:Sodium / Q000494:pharmacology; D013696:Temperature
chemical_list: D000900:Anti-Bacterial Agents; D002352:Carrier Proteins; D024841:Fluoroquinolones; D010879:Piperazines; D000255:Adenosine Triphosphate; D012964:Sodium; C075375:grepafloxacin