Agonist-induced release of expressed VWF proteins from canine VWD aortic endothelial cells. Canine VWD aortic endothelial cells were transiently transfected with Δpro, wild-type VWF, Y87S-VWF, VWFpp, VWFpp*C3α, or VWFpp + Δpro (trans). The culture media were harvested from transfected cells, the cells washed with HBSS, then cells were incubated with either 2 μM PMA or OptiMEM (control) for 45 minutes. The incubation media were collected, and the amount of VWF or VWFpp was quantitated by ELISA. (A) The concentration of released Δpro, wild-type VWF, and Y87S-VWF was determined by VWF ELISA. (Legend: /C = control and /P = PMA treated) (B) The concentration of released VWFpp, VWFpp*C3α, and VWFpp + Δpro (trans) were determined by VWFpp ELISA. Wild-type VWF, Y87S-VWF, and VWFpp + Δpro (trans) were released in response to PMA, while Δpro, VWFpp, and VWFpp*C3α did not show a significant increase in protein release.