Expression and function of rat urothelial P2Y receptors

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Abstract
The control and regulation of the lower urinary tract are partly mediated by purinergic signaling. This study investigated the distribution and function of P2Y receptors in the rat urinary bladder. Application of P2Y agonists to rat urothelial cells evoked increases in intracellular calcium; the rank order of agonist potency (pEC50 ± SE) was ATP (5.10 ± 0.07) > UTP (4.91 ± 0.14) > UTPγS (4.61 ± 0.16) = ATPγS (4.70 ± 0.05) > 2-methylthio adenosine 5′-diphosphate = 5′-(N-ethylcarboxamido)adenosine = ADP (2/P2Y4 receptors, with a relative lack of contribution from other P2Y or adenosine receptors. Real-time PCR, Western blotting, and immunocytochemistry confirmed the expression of P2Y2 and to a lesser extent P2Y4 in the urothelium. Immunocytochemical studies revealed expression of P2Y2 staining in all layers of the urothelium, with relative absence of P2Y4. P2Y2 staining was also present in suburothelial nerve bundles and underlying detrusor smooth muscle. Addition of UTP and UTPγS was found to evoke ATP release from cultured rat urothelial cells. These findings indicate that cultured rat urothelial cells functionally express P2Y2/P2Y4 receptors. Activation of these receptors could have a role in autocrine and paracrine signaling throughout the urothelium. This could lead to the release of bioactive mediators such as additional ATP, nitric oxide, and acetylcholine, which can modulate the micturition reflex by acting on suburothelial myofibroblasts and/or pelvic afferent fibers.