Phosphatase inhibitors enhance calcium influx in PMA-treated RBCs.

Cell suspensions of Fluo-3/am–loaded RBCs were pretreated with (A) 1 μM okadaic acid (thin line) or DMSO (thick line) for 10 minutes or (B) 0.4 μM calyculin A (thin line) or DMSO (thick line) for 2.5 minutes and then stimulated with 3 μM PMA. Calcium influx was monitored by flow cytometry. For maximum effect, RBCs were suspended in PBS-G buffer because the intrinsic phosphatase inhibitor activity associated with HEPES tended to reduce the magnitude of the inhibitor stimulation.35 Tracings representative of 3 different donors are shown.