FIGURE 5.

Inhibiting GSK3α/β activity in mouse and human platelets increases thrombin-mediated platelet aggregation and ATP secretion. A, washed human platelets were incubated with the indicated concentrations of the GSK3α/β inhibitor CHIR99021 for 10 min, extracted in Nonidet P-40, and in vitro GSK3α/β activity was analyzed using the substrate peptide RRAAEELDSRAGS(P)PQL. In vitro kinase activity is expressed as a percentage of GSK3α/β activity obtained in the absence of CHIR99021 (A, mean ± S.E. (error bars) n = 3). (i), washed mouse (B, C, and F) and human (C, D, and G) platelets were stimulated with 0.1 unit/ml thrombin (B and C), 1 μm SFLLRN (D and E), or 0.8 μg/ml collagen-related peptide (CRP) (F and G). Aggregation (B, D, F, and G) and ATP secretion (C and E) were subsequently recorded for 5 min. Traces are representative of four independent experiments. (ii), the bar graphs (B–G) indicate the average increase in aggregation and ATP secretion (nmoles, mean ± S.E., n = 4). *, p < 0.05; **, p < 0.01 (Student's paired t test).