IGF-1 potentiates platelet aggregation in a dose-dependent manner. Washed platelets were incubated with the indicated concentration of IGF-1 for 5 minutes before stimulation with 0.5 μM of the PAR-1 agonist SFLLRN (A), 0.1 μM CRP (B), 0.5 μM ADP (C), or 0.1 μM U46619 (D). Alternatively, IGF-1 (100 nM) was added at various time points (see indicated) before or after stimulation with 0.5 μM SFLLRN (E). Aggregation was subsequently recorded in a Chrono-log 490–4D aggregometer for a total of 5 minutes. Results are representative of 8 (A) and 3 (B-E) experiments. One tick mark on the y-axis represents 20% increase in light transmission.