Clarithromycin transport by gingival fibroblasts and epithelial cells

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 [H-3]-clarithromycin. We assayed clarithromycin transport by measuring cell-associated radioactivity over time. Fibroblasts and epithelial cells rapidly accumulated clarithro mycin, attaining steady-state intracellular concentrations within 15 minutes. Incubation in medium containing 2 mu g/mL clarithromycin yielded steady-state intracellular concentrations of 75.8 mu g/mL in fibroblasts and 6.6 mu g/mL in SCC-25 cells. Clarithromycin transport exhibited Michaelis-Menten kinetics and was inhibited below 37 degrees C. The Michaelis constants for fibro blasts and SCC-25 cells were 78.4 and 227 mu g/mL, respectively, while the maximum transport velocities were 264 and 381 ng/min/10(6) 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.