FIGURE 1.

Major contribution of PI3K to GPVI-induced versus thrombin receptor-induced Ca²⁺ responses in absence of autocrine mediators. Human platelets, treated with aspirin and loaded with Fura-2, were preincubated for 10 min with Me₂SO vehicle (control), wortmannin (0.1 μm), or LY-294002 (10 μm) in the presence of apyrase (0.6 unit/ml). The platelets were stimulated with GPVI ligand, CRP (5 μg/ml), or convulxin (70 ng/ml), or with thrombin (10 nm), in the presence of 1 mm EGTA or 1 mm CaCl₂. A, effect of wortmannin (WT) on CRP-induced [Ca²⁺]_i increases. B, quantitative effect of wortmannin and LY-294002 on integrated Ca²⁺ responses in the presence of EGTA or CaCl₂. Per agonist, time-[Ca²⁺]_i integrals of the relevant control condition were set at 100%. C, effect of wortmannin on convulxin-induced Ca²⁺ mobilization and secondary Ca²⁺ entry (1 mm CaCl₂). Representative traces are shown. Means ± S.E. (n = 4–5); *, p < 0.05 compared with control.