ET-1 induces skin inflammation. A: ET-1 in various concentrations or vehicle was injected intradermally into ears of C57BL/6 mice, and increases in ear swelling were measured as a parameter of inflammation. B: ET-1-induced ear swelling in C57BL/6 mice pretreated with the ET receptor antagonists BQ-123 (ETA, 10−4 M), BQ-788 (ETB, 10−4 M), or vehicle (0.9% NaCl, 200 μl i.v.). Ear swelling is shown 1 hour after ET-1 injection (20 pmol in 20 μl). C: Passive cutaneous anaphylaxis was induced in C57BL/6 mice by sensitizing with IgE anti-DNP (100 ng in 20 μl i.d.) and subsequent challenge 24 hours later with DNP-human serum albumin (400 μg in 100 μl i.v.). D: Ears of ET-1-, vehicle-, or IgE+antigen-injected mice were harvested 6 hours after injection and processed for histochemistry. The extent of MC degranulation was then assessed in alkaline Giemsa-stained 1-μm sections by quantitative histomorphometry at ×400. Data pooled from three (A) or two (B) independent experiments. All data shown as means ± SEM. *P = <0.05, **P = 0.01, ***P = <0.005.