Inhibition of stretching-evoked ATP release from bladder mucosa by anticholinergic agents

Objective: • To determine whether muscarinic receptor antagonism affected stretch-induced release of ATP. Materials and methods: • Mucosal strips, dissected from Guinea pig (male, 450g; n = 10) urinary bladder, were placed in horizontal organ baths and superfused with Ca2+-free Tyrode's solution. • Superfusate samples were taken pre- and post- intervention (rapid stretch or relaxation) and ATP concentration quantified using a luciferin-luciferase assay. • The effect of muscarinic acetylcholine receptors antagonism on ATP release was assessed by addition of methoctramine (1 μM) and 4-DAMP (10 nM). Results: • Rapid stretch (0 to 13.3 ± 1.2 mN; no. strips = 20) increased [ATP] in the superfusate to a median three-fold increase over basal levels. • Following a period of equilibration, tension in the mucosal strips relaxed until it had reached a new steady-state after 60 minutes and stretch was repeated. In the presence of 4-DAMP (10 nM) or methoctramine (1 μM), [ATP] following stretch reduced to 61% and 20%. By contrast, [ATP] from mucosa-matched controls, perfused with vehicle, increased in response to stretch by 391 and 1500%, respectively. • Rapid relaxation also stimulated ATP release. This release did not appear to be sensitive to 4-DAMP or methoctramine. Conclusion: • An alteration of resting mucosal tension is the key determinant of ATP release, as ATP is released from the mucosa in response to both stretch and relaxation. • Muscarinic receptor antagonism inhibits stretch-evoked ATP release from bladder mucosa, suggesting anti-cholinergic agents used to treat human lower urinary tract pathologies act on urothelial muscarinic receptors.