Effect of TTN on [Ca++]i in human PMNs. Panel A: Representative tracings showing the effect of TTN 100 μM (added at arrow) on [Ca++]i in FURA-2-loaded cells under standard conditions (left) and after 60-s incubation with PMA 100 ng/ml (center) or α-PMA 100 ng/ml (right). Panel B: Concentration-response relationship for the effect of PMA (empty circles) and lack of effect of α-PMA (empty square) on TTN 100 μM-induced [Ca++]i rise. Data are expressed as percentage of the effect of TTN alone (filled circle). Each point is the mean ± SD of 3 separate experiments.