Pulmonary vascular response to acetylcholine in isolated rat lungs treated with intratracheal bleomycin.

We tested the hypothesis that during alveolar hypoxia the vasodilator response to acetylcholine (ACh) is impaired in lungs injured by intratracheal bleomycin. Isolated rat lungs were ventilated with normoxic (21% O2) or hypoxic (2% O2) gas and perfused with homologous blood. The effect of ACh on pulmonary vascular resistance was estimated during ongoing hypoxic pulmonary vasoconstriction (HPVC) after the temporal pattern of HPVC was established. The magnitude of the decrease in pulmonary vascular resistance was significantly smaller in the bleomycin-treated group (group B, n = 7) than in the saline-treated group (group S, n = 7) (p less than 0.05). The magnitude of HPVC itself did not differ between groups. The pulmonary vascular reactivities to angiotensin II and KCl were similar in the two groups (group S, n = 4, group B, n = 5). At any given transpulmonary pressure the lung volumes of group B (n = 5) were significantly smaller than those of group S (n = 4) (p less than 0.01). We conclude that vascular dilation in response to ACh during ongoing HPVC was impaired in bleomycin-injured rat lungs.