Antisense knockdown of flk1 in zebrafish abolishes dihydroartemisinin (DHA)-induced pericardial edema. (A–C) Embryos were treated with DMSO. (D–F) Embryos were treated with 2.5 mg/L DHA. (G–I) Embryos were treated with 10 mg/L DHA. NC-MO injected embryos are shown in panels A, D, and G. flt1-MO injected embryos are shown in panels B, E, and H. flk1-MO injected embryos are shown in panels C, F, and I. The scale bar represents 500 μm for all panels.