Expression and function of bradykinin B1 and B2 receptors in normal and inflamed rat urinary bladder urothelium.
The bladder urothelium exhibits dynamic sensory properties that adapt to changes in the local environment. These studies investigated the localization and function of bradykinin receptor subtypes B1 and B2 in the normal and inflamed (cyclophosphamide (CYP)-induced cystitis) bladder urothelium and their contribution to lower urinary tract function in the rat. Our findings indicate that the bradykinin 2 receptor (B2R) but not the bradykinin 1 receptor (B1R) is expressed in control bladder urothelium. B2R immunoreactivity was localized throughout the bladder, including the urothelium and detrusor smooth muscle. Bradykinin-evoked activation of this receptor elevated intracellular calcium (EC(50) = 8.4 nM) in a concentration-related manner and evoked ATP release from control cultured rat urothelial cells. In contrast, B1R mRNA was not detected in control rat urinary bladder; however, following acute (24 h) and chronic (8 day) CYP-induced cystitis in the rat, B1R mRNA was detected throughout the bladder. Functional B1Rs were demonstrated by evoking ATP release and increases in [Ca(2+)](i) in CYP (24 h)-treated cultured rat urothelial cells with a selective B1 receptor agonist (des-Arg(9)-bradykinin). Cystometry performed on control anaesthetized rats revealed that intravesical instillation of bradykinin activated the micturition pathway. Attenuation of this response by the P2 receptor antagonist PPADS suggests that bradykinin-induced micturition facilitation may be due in part to increased purinergic responsiveness. CYP (24 h)-treated rats demonstrated bladder hyperactivity that was significantly reduced by intravesical administration of either B1 (des-Arg(10)-Hoe-140) or B2 (Hoe-140) receptor antagonists. These studies demonstrate that urothelial expression of bradykinin receptors is plastic and is altered by pathology.
Chopra
Bikramjit
B
A1207 Scaife Hall, Department of Medicine-Renal Division, University of Pittsburgh, 3550 Terrace Street, Pittsburgh, PA 15261, USA.
Barrick
Stacey R
SR
Meyers
Susan
S
Beckel
Jonathan M
JM
Zeidel
Mark L
ML
Ford
Anthony P D W
AP
de Groat
William C
WC
Birder
Lori A
LA
D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D002463:Cell Membrane Permeability; D002478:Cells, Cultured; D003520:Cyclophosphamide; D003556:Cystitis / Q000139:chemically induced / Q000276:immunology / Q000378:metabolism*; D005260:Female; D005786:Gene Expression Regulation; D051381:Rats; D017207:Rats, Sprague-Dawley; D043783:Receptor, Bradykinin B1 / Q000276:immunology / Q000378:metabolism*; D043782:Receptor, Bradykinin B2 / Q000276:immunology / Q000378:metabolism*; D014018:Tissue Distribution; D001743:Urinary Bladder / Q000276:immunology / Q000378:metabolism*; D019459:Urothelium / Q000276:immunology / Q000378:metabolism*
D043783:Receptor, Bradykinin B1; D043782:Receptor, Bradykinin B2; D000255:Adenosine Triphosphate; D003520:Cyclophosphamide