FIG. 2.

Effects of ehrlichial infection and inhibitors on production of IP₃ in THP-1 cells. (A) Rapid release of IP₃ induced by ehrlichial infection. The release reached a peak (approximately threefold) at 1.5 min p.i. and decreased to the background level within 5 min. (B) Release of IP₃ induced by E. chaffeensis (EC) prevented by pretreatment with inhibitors of PTK, PLC, and TGase. Cells were pretreated with or without inhibitors 1 h before ehrlichial infection, and IP₃ samples were extracted with perchloric acid at different times (A) or 1.5 min p.i. (peak release of IP₃) (B). The release of IP₃ was determined by measuring competitive inhibition of binding of ³H-labeled IP₃ to IP₃-binding protein. The values are means ± standard deviations (n = 3) and are representative of the results of three independent experiments.