Purpose: Although the sensory and motor roles of the purinergic system in the bladder are well proven in animal species, there is increasing evidence that it may have an important role in humans. In addition, it may be important in the pathophysiology of bladder dysfunction. We established the level of adenosine triphosphate (ATP) release from porcine and normal human bladders.
Materials and methods: Bladder strips from patients with a urodynamically proven stable bladder undergoing surgery for stress incontinence and those undergoing cystectomy for cancer with no lower urinary tract symptoms were subjected to varying degrees of stretch (up to 50%) and electric field stimulation (10 to 40 Hz). A luciferase assay was used to quantify ATP release.
Results: Significantly increased ATP release over baseline was induced by mechanical and electrical stimulation (each p <0.05). Mean ATP release +/- SE from porcine bladders (38.2 +/- 1.9 pM/gm tissue following stretch and 19.9 +/- 6.5 pM/gm following electrical stimulation) was comparable to the release from human bladders (26.1 +/- 2.4 pM/gm tissue following stretch and 29.9 +/- 1.0 pM/gm following electrical stimulation). The main source of ATP release was the urothelium and not the muscle (p <0.05). This ATP release following stretch was not tetrodotoxin sensitive.
Conclusions: The characteristics of ATP release from porcine and human bladders are similar and, therefore, the pig is a good model for humans. The main source of ATP release is urothelium from predominantly nonneuronal sources. This study supports a sensory role for ATP. An increased role for this purinergic neurotransmission may result in functional motor as well as sensory bladder disorders.