β−Adrenergic receptor subtype expression in myocyte and non-myocyte cells in human female bladder
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β3-Adrenergic receptor agonists are currently under clinical development for the treatment of overactive bladder, a condition that is prevalent in postmenopausal women. These agents purportedly relax bladder smooth muscle through a direct action at the myocyte β3-receptor. The aim of this study was to examine the expression of the individual beta-adrenergic receptors in full thickness sections from ageing human female bladder. We obtained a series of rabbit polyclonal antibodies generated against each of the three β-adrenergic receptors, and validated their receptor specificity in CHOK1 cells expressing each of the individual receptors. Immunostaining for β1, β2, and β3 were each more prominent in the urothelium than in the detrusor, with all receptors expressed in the same cell types, indicating co-expression of all three receptors throughout the urothelium in addition to the detrusor. Staining of all receptors was also observed in suburothelial myofibroblast-like cells, intramural ganglion cells, and in Schwann cells of intramural nerves. The β3-receptor in the human urothelium appears to be functional, as two different selective β3-receptor agonists, TAK677 and BRL37344, stimulate cAMP formation in UROtsa cells. Densitometry analysis indicates a persistent expression of all receptors throughout the bladder with increasing age, with the exception of the β2-receptor in the urothelium of the trigone, which appears to decrease slightly in older women. These data indicate that β3-receptor expression is maintained with age, but may function in concert with other β-receptors. Activation of the myocyte receptor may be influenced by action on non-myocyte structures including the intramural ganglion cells and myofibroblasts.