Purines modulate urinary bladder arteriolar tone

Bladder dysfunction affects millions of people, but few effective treatments are available. In humans, changes in bladder function correlate to changes in blood flow. In rodent models, loss of bladder blood flow directly causes bladder overactivity. This makes the vasculature a novel target for treating bladder dysfunction. Unlike most vessels of similar size, bladder arterioles do not exhibit myogenic tone, suggesting other molecular mechanisms regulate bladder blood flow. One such molecule is ATP, a potent vasoconstrictor released during bladder filling and known to activate purinergic P2X1 receptors in vascular smooth muscle and P2X4 receptors in the endothelium. Thus, the objective of this study was to determine which purinergic P2X receptors are present in urinary bladder arterioles and if they regulate purinergic vasoconstriction. We hypothesized that P2X1 receptors cause vasoconstriction and P2X4 receptors cause endothelium-dependent vasodilation in urinary bladder arterioles. Urinary bladder arterioles from 10 to 16-week-old male C57Bl/6 mice were isolated and cannulated for pressure myography. Diameter was measured in response to the P2X receptor agonist α,βMethylene-ATP (α,βMe-ATP; 100 nM). Constriction to α,βMe-ATP was measured before and after exposure to the nonselective P2X receptor antagonist PPADS (100 μM), selective P2X1 antagonist NF 279 (10 μM), or the selective P2X4 antagonist 5-BDBD (10 μM). In some experiments, the endothelium was denuded via air bubble through the lumen. The presence or absence of endothelium was verified using the muscarinic receptor agonist carbachol (1 μM). Urinary bladder arterioles constricted to α,βMe-ATP in a biphasic manner, with rapid vasoconstriction followed by a rapid partial loss of tone. The loss of tone plateaued, resulting in a stable steady-state constriction relative to baseline. We expected that blocking P2X1 receptors would eliminate the entire response to α,βMe-ATP, whereas blocking P2X4 receptors would prevent the loss of tone and augment the steady-state constriction to α,βMe-ATP. As expected, both PPADS and NF 279 blocked the entire response to α,βMe-ATP. However, 5-BDBD did not prolong α,βMe-ATP-induced constriction. Instead, 5-BDBD augmented the loss of tone, resulting in a monophasic constriction that rapidly returned to baseline. Surprisingly, PPADS alone caused a prolonged constriction in urinary bladder arterioles that was not present with NF 279 or 5-BDBD. This constriction was significantly greater in endothelium-denuded vessels. This response is also bladder specific, as the constriction was significantly reduced in mesenteric arterioles. Together, these data suggest that α,βMe-ATP constricts bladder arterioles by activating P2X1 receptors. They also suggest that P2X4 receptors are not vasodilatory in bladder arterioles; they instead maintain the steady-state constriction to α,βMe-ATP. Lastly, urinary bladder arterioles may possess intrinsically active and PPADS-sensitive purinergic receptors that help maintain arteriolar dilation. Overall, these data introduce purinergic signaling as a potential modulator of bladder blood flow and a novel target for treating bladder dysfunction. Future experiments will further explore endothelial vs. smooth muscle purinergic receptor function and the role of purinergic nerves in regulating bladder vascular tone. Funded by NIH grants R01-DK135696, R01-DK119615, P01-HL152951 and T32-GM142521. This abstract was presented at the American Physiology Summit 2026 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.