Extracellular metabolism of 3′,5′-cyclic AMP as a source of interstitial adenosine in the rat airways

In the respiratory tract, intracellular 3',5'-cAMP mediates smooth muscle relaxation triggered by the β2-adrenoceptor/Gs protein/adenylyl cyclase axis. More recently, we have shown that β2-adrenoceptor agonists also increase extracellular 3',5'-cAMP levels in isolated rat trachea, which leads to contraction of airway smooth muscle. In many other tissues, extracellular 3',5'-cAMP is metabolized by ectoenzymes to extracellular adenosine, a...