Adenosine and hypoxic pulmonary vasodilation

We have previously shown that after exposure to an inspired O₂ tension 2) (PI(O₂)) 18 or 0 Torr]. In comparison with untreated lungs, the time course of pulmonary arterial pressure at constant flow in lungs treated with ADase (24 mg protein or 6,000 U) was not different; however, when the vessels were constricted at PI(O₂) 25 Torr, ADase prevented vasodilator responses to adenosine administered into either the perfusate or the airways, indicating penetration of active ADase into the interstitium. Unless adenosine released endogenously into the interstitium during hypoxia was somehow protected from the ADase which reached the interstitium, these results indicate that hypoxic pulmonary vasodilation was not mediated by adenosine.