The role of adenosine in hypoxic pulmonary vasoconstriction in the anaesthetized rat

In nine artificially ventilated rats anaesthetized with Saffan, systemic hypoxia induced a tachycardia followed by a bradycardia, a fall in systemic arterial pressure and an increase in pulmonary artery pressure (PPA) indicating pulmonary vasoconstriction. This increase in PPA was abolished by the adenosine receptor antagonist 8‐phenyltheophylline (8‐PT, 10 mg kg‐1 I.V.). Further, in seven rats the Pa,O2 achieved during hypoxia was greater after 8‐PT than before (38 vs. 40 mmHg). We suggest that adenosine makes a major contribution to hypoxia‐induced pulmonary vasoconstriction in the rat. The better maintenance of Pa,O2 during hypoxia may reflect improved perfusion of well‐ventilated alveoli.