Effect of MK integrin blockade and inhibition of actin polymerization.

(A) The effects of disintegrin on proplatelet formation. Both kistrin (10 ng/mL) and EMF-10 (50 ng/mL) markedly decreased the numbers of proplatelet-bearing MKs (shown in the left-hand set of bars), expressed as a percentage of control diluent (dimethylsulfoxide; DMSO). The numbers of viable MKs, shown in the right set of bars, are only modestly affected. ░, DMSO; ▧, kistrin; ▨, EMF-10. (B) We tested whether actin reorganization is essential for MK proplatelet formation using cytochalasin D (5 μmol/L). Cytochalasin D significantly decreased the number of proplatelet-bearing MKs in culture. However, at this dose of cytochalasin, some actin aggregates could still be observed. ░, DMSO; ▨, cyto D 0.5 μM.