Kinetics of the uptake of rifampicin and tetracycline into mouse macrophages. In vitro study of the early stages.

The in vitro uptake by mouse peritoneal macrophages, of chlortetracycline (by fluorescence microscopy) and of tetracycline and rifampicin (by scintillation spectrometry of radioactive antibiotics) has been studied over a six hours period, using various concentrations of the antibiotics, close to the therapeutic concentrations. The incidence of the conditions of the assays, especially that of the use of heterologous serum for the cultivation of cells, has been investigated; a medium supplemented with homologous serum at low concentration has been devised with the technique. The uptake of these antibiotics was a three-phases process suggesting the superposition to a passive diffusion of either an active incorporation, or a restriction of the outflow (perhaps associated). This led to a rather high concentration of the antibiotics into cells, although other studies have shown that this concentration is not as active on intracellular bacteria as one could expect from the in vitro sensitivity.