Epinephrine releases FVIII. (A) Epinephrine releases FVIII and VWF from T2F8 transgenic mice. Epinephrine was administrated to animals and plasma samples were collected before and 30 minutes after infusion for FVIII:C and VWF:Ag assays. The levels of both FVIII and VWF significantly increased after epinephrine infusion in T2F8^Tg mice; †P < .05. (B) Epinephrine releases endogenous mouse FVIII and VWF from WT mice. The levels of both FVIII and VWF significantly increased after epinephrine infusion in WT mice; †P < .05. (C) Saline administration control in T2F8^Tg mice. There was no significant difference in the levels of either FVIII or VWF before versus after saline administration. These studies demonstrated that targeting FVIII to endothelial cells establishes a releasable pool of FVIII together with VWF.