FIG. 3.

Effects of ehrlichial infection and inhibitors on [Ca²⁺]_i in a population of cells. [Ca²⁺]_i increased rapidly and transiently in THP-1 cells infected with E. chaffeensis (E.C.) (A), but the increase was prevented by pretreatment with inhibitors of calcium mobilization (verapamil and TMB-8) (B) or inhibitors of PLC (neomycin), PTK (genistein), and TGase (MDC) (C). The intracellular calcium levels in fluo-3-loaded THP-1 cells were determined with a fluorometer as described in Materials and Methods. The inhibitors were added to cells 1 h before the assay, and host-cell-free E. chaffeensis was added to THP-1 cells at the time indicated by the vertical arrow (approximately 50 s p.i.). Assays were carried out at 30°C in a circulating water bath. Fluorescence was measured at 525 nm at 5-s intervals, and K_d was calibrated by using a calcium calibration kit from Molecular Probes. The values are representative of the results of at least four independent experiments. moi, multiplicity of infection.