High potassium-evoked release of ATP from rabbit pulmonary artery via endogenous noradrenaline.

1. High potassium 30 mM and noradrenaline at 10 microM significantly evoked the release of ATP and produced remarkable vasoconstriction in the rabbit pulmonary artery. 2. Phentolamine and prazosin at 0.1 microM inhibited ATP release but not vasoconstriction by 30 mM potassium. 3. 30 mM potassium significantly evoked the release of noradrenaline. 4. There was a significant positive correlation between the amounts of release of total purines, sum of ATP, ADP, AMP and adenosine, and noradrenaline evoked by 30 mM potassium. 5. 30 mM potassium-evoked ATP release was significantly reduced by denudation of endothelium.