Fig. 4. Effects of increasing concentrations of endothelin-1 (ET-1) on the relative tension of alligator intrapulmonary arteries: non-treated vessels, vessels incubated with either the specific ET_A-receptor antagonist BQ-123 (3x10^–6 mol l^–1), the specific ET_B-receptor antagonist BQ-788 (3x10^–6 mol l^–1) or the general ET-receptor antagonist tezosentan (10^–5 mol l^–1). Contraction is expressed relative to the contraction induced by 60 mmol l^–1 KPSS. Values are means ± s.e.m., N=7 (ET-1) and N=4 (ET_B, ET_A and tezosentan). An asterisk denotes a significant difference (P<0.05) from control treatment with ET-1 alone, evaluated by a two-way ANOVA followed by a Tukey post hoc test.