Requirement for endogenous apelin for inhibition of VEGF- or histamine-induced vascular edema. (A-B) Vessel permeability was assessed by the Miles assay. Apelin-deficient (KO) and WT mice (A) or K14-apelin Tg and WT mice (B) were injected with 15 μL of PBS in the presence or absence of rhVEGF165 (100 ng/mL) or histamine (100μM) intradermally. Thirty minutes after injection, the inner side of the dorsal skin was inspected. Top panels: Representative images of the vascular leakage. Bottom panels: Quantification of extravasated Evans blue dye content eluted from dissected skin (mean ± SEM; n = 10). *P < .05.