PLCγ2^–/– platelets show a limited Ca²⁺ increase, which is inhibited by U73122. (A) Washed platelets from wild-type (WT) and PLCγ2^–/– mice were stimulated with 40 μg/mL convulxin (cvx) or 1 U/mL thrombin (thr). Intracellular Ca²⁺ was measured by the ratio of Fura-PE3 emissions. (B) Platelets were preincubated with 1 μM U73142 or 1 μM U73122 for 5 minutes. Then they were stimulated and Ca²⁺ was measured as described for panel A. (C) Washed platelets from PLCγ2^–/– were preincubated with 4 μM U73143 or 4 μM U73122 for 5 minutes and stimulated with 40 μg/mL convulxin for 5 minutes in the presence of fibrinogen (200 μg/mL).