FIG. 3.

Platelet antagonist PGI₂ inhibits α-thrombin-induced activation of Ral. Platelets were treated with 20 ng of PGI₂ per ml for 2 min prior to stimulation with 0.1 U of α-thrombin (α-thr) per ml or were stimulated with 0.1 U of α-thrombin per ml alone. Ral activation was analyzed as described in the legend to Fig. 2. ––, resting platelets.