The inhibitory effect of ADP scavengers on FcγRIIA-mediated PtdIns(3,4,5)P₃ synthesis is reversed by epinephrine.

³²P-labeled platelets were incubated with or without A3P5PS, CP-CPK, and CP-CPK and 1-μmol/L epinephrine (1 minute, 37°C) and activated by FcγRIIA cross-linking (A). The effect of 1-μmol/L epinephrine alone was assessed. Increasing concentrations of CP-CPK (B) and AR-C69931MX (C) were tested, and the inhibitory effects of these compounds were overcome in a dose-dependent manner by epinephrine (B,C). After 2 minutes of stimulation, lipids were extracted, and the radioactivity incorporated in PtdIns(3,4,5)P₃ was determined as described in “Materials and methods.” Data are expressed as a percentage of PtdIns(3,4,5)P₃ produced compared with control (100% being the production obtained by FcγRIIA clustering at 2 minutes) and are means ± standard errors of 3 independent experiments (A) or representative. *,***Significant difference (P < .05) and (P < .001), respectively, according to Student ttest.