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Antimicrobial Agents and Chemotherapy, October 2000, p. 2609-2614, Vol. 44, No. 10
Section of Periodontology, College of
Dentistry,1 and Department of Molecular
and Cellular Biochemistry, College of
Medicine,2 The Ohio State University Health
Sciences Center, Columbus, Ohio
Received 28 December 1999/Returned for modification 26 April
2000/Accepted 22 June 2000
Human monocytes transport and accumulate ciprofloxacin and other
fluoroquinolones. Although little is known about the mechanisms of
transport, we expected monocytes to be similar to other cells of
myeloid lineage. In the present study, monocyte fluoroquinolone transport was characterized and compared to the corresponding transport
pathways of human polymorphonuclear leukocytes (PMNs) and HL-60 cells.
Ciprofloxacin transport by monocytes was saturable, temperature
dependent, sodium independent, and relatively insensitive to pH.
Quiescent monocytes transported ciprofloxacin with a
Km of 171 µg/ml and a
Vmax of 32.7 ng/min/106 cells.
Adenine competitively inhibited ciprofloxacin transport by quiescent
monocytes (Ki = 3.8 mM), but nucleosides had no
significant inhibitory effect. In all of these respects, transport by
monocytes was similar to that observed for quiescent PMNs and immature
HL-60 cells. Unlike PMNs, however, monocytes and immature HL-60 cells did not exhibit dramatically enhanced ciprofloxacin transport when
activated by phorbol myristate acetate (PMA). Consistent with this
finding, HL-60 cells committed to granulocytic differentiation exhibited a significant component of PMA-inducible ciprofloxacin transport activity, while HL-60 cells committed to monocytic
differentiation did not. In PMNs, the PMA-inducible component of
transport appeared to be mobilized from a granule compartment, since
its activity could be modulated by agents that enhance or inhibit
stimulated degranulation. Thus, quiescent monocytes, PMNs, and HL-60
cells take up ciprofloxacin via similar energy-dependent transport
mechanisms. Unlike granulocytes, monocytes do not express a second,
higher-affinity pathway for ciprofloxacin accumulation when they are
activated by PMA.
0066-4804/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Fluoroquinolone Transport by Human Monocytes: Characterization
and Comparison to Other Cells of Myeloid Lineage
*
Corresponding author. Mailing address: College of
Dentistry, The Ohio State University, 305 West 12th Ave., Columbus, OH
43210. Phone: (614) 292-1322. Fax: (614) 292-2438. E-mail:
walters.2{at}osu.edu.
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