Fig. 5. The association of lipid rafts with the actin cytoskeleton is reversible. Platelets (3x10⁹ cells) were stimulated by TRAP (5 µM) as in Fig. 4A. In order to reverse platelet aggregation, 50 nM wortmannin (A and B, left panels) or 400 µM SR-121566 (A and B, right panel) was added 2 and 1.5 minutes after addition of the agonist, respectively. (A) Platelet aggregation profiles show disaggregation after the addition of wortmannin (left panel) or SR-121566 (right panel). (B) The actin cytoskeletons were isolated at 0, 3 or 7 minutes and their cholesterol (O) and SM () content was determined as in Fig. 1A. The drop in cholesterol and SM concomitant with platelet disaggregation induced either by wortmannin or by SR-121566 (dotted lines) illustrates a transient association of rafts with the cytoskeleton under these conditions. Results shown are mean±s.d. of two (for cholesterol) or three (for SM) independent experiments.