Platelets induce proliferation of SMC. SMC were cultured in 24-well culture plates until they reached confluency, washed with serum-free medium, and incubated for 24 hours in serum-free medium containing insulin and transferrin (IT-medium). The cultures were then washed, platelets at the denoted ratios added, and the cocultures incubated with or without the respective stimuli (72 hours). Subsequently radiolabeled thymidine was added for 24 hours and thymidine incorporation of cells measured in a scintillation counter (Proliferation). For IL-6 measurement parallel cultures were washed and incubated with the stimuli for 24 hours (IL-6). Two additional experiments showed comparable results.