Effect of exogenous adenosine and its monophosphate on the contractile response to acetylcholine in the human isolated detrusor muscle strips

1 Adenosine (0.1-1 mM) or its 5'-monophosphate (5'-AMP) induced a concentration-dependent relaxation of tension caused by acetylcholine (0.2 μM) in human urinary bladder detrusor strips. 2 This effect was antagonized concentration dependently by theophylline at an apparent pA₂ value of about 5. 3 Maximum relaxation by adenosine or 5'-AMP never exceeded 50% and 80%, respectively, of acetylcholine-induced tension. Relaxation by some β₂- adrenoceptor agonists (0.1-0.2 mM) or norepinephrine was limited to about 50% of maximum. 4 The responses to adenosine and terbutaline were additive, causing full relaxation, and suggesting mobilization of distinct mechanisms underlying muscle relaxation.