Effect of PF4 and various peptides (p17-58, p34-58, and p47-58) of PF4 (0, 0.2, 2.2, 22, 76.5, 130, and 630 nmol/L) on the formation CFU-MK. Values are expressed as the mean ± SEM of triplicate determination obtained from three separate experiments. *P < .01 as compared with control value determined by the Student's t-test. One hundred percent (100%) corresponds to the number of megakaryocyte colonies (70 colonies/mL) in control cultures.