Multimer analysis of Rab27a knockdown and mock-treated HUVECs. (A) HUVECs were treated in 2 consecutive rounds with siRNA oligonucleotides directed against Rab27a or a control oligonucleotide. Samples of serum-free media were acquired after 30 minutes with and without 100 ng/mL PMA. The secreted VWF was concentrated 20-fold and loaded onto a 1.4% agarose multimer gel. The VWF multimer pattern was determined in 3 separate experiments; a representative gel is shown here. (B) Densitometry of multimer gel with the lowest-molecular-weight multimers appearing as peaks to the right of the graph.