4N1K and TS1 induce the aggregation of platelets adherent to immobilized collagen. Washed platelets were allowed to adhere on immobilized collagen (10 μg/mL). After 60 minutes, platelets were fixed with 1% paraformadehyde, permeabilized with 0.1% Triton X-100, and stained with rhodamine-phalloidin. Treatments added 15 minutes before plating were (A) no treatment; (B) 4N1K (50 μmol/L); (C) 4NGG (50 μmol/L); (D) TS1 (50 μg/mL); (E) apyrase (10 U/mL); (F) apyrase (10 U/mL) plus 4N1K (50 μmol/L); (G) PGE1 (1 μmol/L); (H) PGE1 (1 μmol/L) + 4N1K (50 μmol/L).