Fig. 3. Effects of hypoxia (45 min, P_O2<5 mmHg) on alligator intrapulmonary arteries. (A) Relaxed vessels (baseline), (B) vessels preconstricted with serotonin (5-HT) and (C) vessels preconstricted with endothelin-1 (ET-1) with an intact endothelium (black bars) or denuded (grey bars). Contraction is expressed relative to the contraction induced by 60 mmol l^–1 KPSS. Values are means ± s.e.m., N=3 (A) and N=6 (B,C). Different letters indicate a significant difference (P<0.05) from baseline evaluated by a two-way ANOVA followed by a Tukey post hoc test. Haematoxylin/Eosin staining shows the presence (D) and absence (E) of endothelium in representative vessels (40xmagnifications). The arrow shows endothelial cells.