Dissociation of the SPL/RGS complex during platelet activation by thrombin and TxA₂ mimetics but not by ADP or collagen. (A-B) Human platelets were incubated with the PAR1 agonist, SFLLRN, or the TxA₂ mimetic, U46619, after which lysates were precipitated with anti-RGS10 or anti-RGS18 before being probed for SPL. Error bars represent SEM for the number of replicates indicated if N > 2. The vertical lines in panel A indicate grouping of the results at each time point, not rearrangement of the lanes. (C) Platelets were incubated with ADP ± ASA. (D) Platelets were incubated with collagen ± apyrase and ASA. (C-D) Results are representative of 2 studies each performed with separate donors.