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Clarithromycin Transport by Gingival Fibroblasts and Epithelial Cells

Section of Periodontology, College of Dentistry, The Ohio State University Health Sciences Center, 305 West 12th Avenue, PO Box 182357, Columbus, OH 43218-2357, USA

^* corresponding author, walters.2{at}osu.edu

Macrolide antibiotics penetrate cells, but the mechanism by which this occurs is unclear. The objective of this study was to characterize the mechanisms of clarithromycin uptake by gingival fibroblasts and oral epithelium. Cultured human gingival fibroblasts and SCC-25 cells were incubated with [³H]-clarithromycin. We assayed clarithromycin transport by measuring cell-associated radioactivity over time. Fibroblasts and epithelial cells rapidly accumulated clarithromycin, attaining steady-state intracellular concentrations within 15 minutes. Incubation in medium containing 2 µg/mL clarithromycin yielded steady-state intracellular concentrations of 75.8 µg/mL in fibroblasts and 6.6 µg/mL in SCC-25 cells. Clarithromycin transport exhibited Michaelis-Menten kinetics and was inhibited below 37°C. The Michaelis constants for fibro-blasts and SCC-25 cells were 78.4 and 227 µg/mL, respectively, while the maximum transport velocities were 264 and 381 ng/min/10⁶ cells, respectively. Thus, both types of cells take up clarithromycin via a concentrative active transport system. By increasing intracellular clarithromycin levels, this system may enhance the effectiveness of clarithromycin against invasive periodontal pathogens.

KEY WORDS: macrolides • antimicrobial chemotherapy • aggressive periodontitis