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 microM) 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 beta2-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.