Confocal microscopy of Gα12 and vWF. Mutationally-activated Gα12 stimulates WPB exocytosis. (A) HUVECs were transfected with GFP alone (negative control) or GFP-tagged Gα12^WT or Gα12^Q229L constructs. After 4 h of serum starvation, GFP-expressing HUVECs were incubated for 15 minutes with vehicle (unstimulated) or 25 nM thrombin. WPBs were visualized by vWF immunofluorescent staining (red). Single confocal optical sections (pinhole set to achieve 1 Airy unit) are shown; bars correspond to 20 µm. (B) Fluorescent WPBs per cell were quantified as described in Materials and methods. Red horizontal bars represent median values. *P < .05 by analysis of variance vs unstimulated GFP-alone expressing cells. *,#P < .05 vs all other groups.