Kinetics of thrombin-induced tyrosine phosphorylation of protein substrates in platelets from controls and from three different types of Glanzmann thrombasthenia patients. Washed platelets from control (CONTROL) or patient (PATIENT) were stimulated with 0.05 U/mL thrombin for indicated times under stirring, then solubilized in SDS and analyzed for protein tyrosine phosphorylation by SDS-PAGE followed by Western blotting using a monoclonal antibody specific for phosphotyrosines. Corresponding aggregation rates are indicated [Agg (%)]. (A) Type I Glanzmann thrombasthenia [PATIENT (GTI)]. (B) Type II Glanzmann thrombasthenia [PATIENT (GTII)]. (C) Variant type Glanzmann thrombasthenia [PATIENT (GT var)]. Molecular weights are indicated on the right. The 60 kD band corresponds to c-src and is identified by “src”.