Uptake of flurithromycin by human polymorphonuclear phagocytes: partial characterization of the entry mechanism

The ability of flurithromycin and erythromycin to enter human polymorphonuclear phagocytes were studied and compared by a velocity centrifugation gradient technique. Both macrolides were markedly concentrated by human cells and attained cellular to extracellular concentration ratios (C/E) > or = 10. The incorporation was rapid and essentially complete after 60 min incubation. When PMNs were pretreated with formaldehyde, or incubated at low temperatures (4-25 degrees C) or at low pH, the transport ratios of both molecules were reduced. Sodium fluoride and 2,4-dinitrophenol, which decreased erythromycin uptake, did not affect flurithromycin penetration. Perturbation of cell membrane by phorbol myristate acetate, but not by formyl methionyl leucyl peptide, affected C/E ratios of both antibiotics. The addition of amino acids or nucleosides did not influence their transfer into PMNs.