Expression and localization of pannexin-1 and CALHM1 in porcine bladder and their involvement in modulating ATP release



Publication Details

Sana-Ur-Rehman, H., Markus, I., Moore, K. Hilda., Mansfield, K. Jan. & Liu, L. (2017). Expression and localization of pannexin-1 and CALHM1 in porcine bladder and their involvement in modulating ATP release. American Journal of Physiology: Regulatory, Integrative and Comparative Physiology, 312 (5), R763-R772.


ATP release from urinary bladder is vital for afferent signaling. The aims of this study were to localize CALHM1 and pannexin-1 expression and to determine their involvement in mediating ATP release in the bladder. Gene expression by PCR and immunohistochemistry were performed in the porcine bladder. CALHM1 and pannexin-1 mediated ATP release in response to hypotonic solution (0.45% NaCl) induced stretch and extracellular Ca2+ depletion ([Ca2+]0) was measured in isolated urothelial, suburothelial and detrusor muscle cells. CALHM1 and pannexin-1 mRNA and immunoreactivity were detected in urothelial, suburothelial and detrusor muscle layers with a highest expression on urothelium. Hypotonic stretch caused a 2.7-fold rise in ATP release from all three cell populations (P < 0.01), which was significantly attenuated by the pannexin-1 inhibitor,10Panx1, and by CALHM1 antibody. Brefeldin A, a vesicular transport inhibitor, and ruthenium red, a non-selective CALHM1 channel blocker, also significantly inhibited stretch-mediated ATP release from urothelial cells. [Ca2+]0 caused a marked but transient elevation of extracellular ATP level in all three cell populations. CALHM1 antibody and ruthenium red inhibited [Ca2+]0-induced ATP release from urothelial cells, but their effects on suburothelial and detrusor cells was insignificant. 10Panx1 showed no significant inhibition of [Ca2+]0-induced ATP release in any types of cells. The results presented here provide compelling evidence that pannexin-1 and CALHM1 that are densely expressed in the porcine bladder function as ATP release channels in response to bladder distension. Modulation of extracellular Ca2+ may also regulate ATP release in the porcine bladder through voltage gated CALHM1 ion channels.

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