Protamine and surfen inhibit VEGFR2 phosphorylation in vitro and dermal vascular permeability in vivo. A, immunoblot analysis of VEGFR2 phosphorylation in mBMEC stimulated with VEGF165 (50 ng/ml) or VEGF121 (100 ng/ml) for 5 min. Cells were treated with protamine at the indicated concentration prior to application of VEGF. The immunoblots are representative of three similar experiments. B, immunoblot analysis of VEGFR2 phosphorylation was performed as in A, except that cells were treated with surfen. C, mice were injected intradermally with 200 ng of VEGF165 alone (filled squares) or with 12.5 μg of protamine (open squares), and the amount of Evan's Blue leakage was measured; n = 9. D, mice were injected intradermally with 200 ng of VEGF165 alone (filled squares) or with 54 μm surfen (open squares); n = 9. E, mice were injected with 200 ng of VEGF121 alone (filled squares) or with 54 μm surfen (open squares); n = 11. Experimental and control treatments of the same mouse in C–E are linked with a line. PBS with 0.1% BSA was used as negative control, which showed an average leakage of 0.9 ± 0.1 μg (C), 0.8 ± 0.1 μg (D), and 0.7 ± 0.1 μg (E). pY1175, phospho-Tyr-1175.