Urothelial beta-3 adrenergic receptors in the rat bladder.
OBJECTIVE
To investigate the distribution of beta-3 adrenergic receptors (β(3)ARs) in the rat bladder and to examine the contribution of urothelial β(3)ARs to agonist-induced suppression of bladder reflexes and relaxation of smooth muscle.


METHODS
Bladder tissue was collected from 8- to 10-month old female SD rats. In some samples, the urothelium was surgically separated from the smooth muscle. The expression and localization of βAR mRNA and β(3)AR protein were determined using RT-PCR and immunohistochemistry. Contractile responses to the specific β(3)AR agonists TAK-677 and BRL37344 were measured in bladder strips with or without the urothelium. The contribution of urothelial β(3)ARs to the micturition reflex was assessed in continuous cystometry in urethane anesthetized rats using intravesical delivery of β(3)AR agonists.


RESULTS
RT-PCR detected mRNA of all βARs in urothelium and smooth muscle. Immunostaining detected β(3)ARs throughout the urothelium, in the smooth muscle, myofibroblast-like cells, and in the peripheral nerves. Ovariectomy did not change the distribution of β(3)ARs in any bladder structure. Intravesical administration of TAK-677 and BRL37344 (1-5 × 10(-4) M) decreased voiding frequency and amplitude of bladder contractions. In bladder strips in vitro both β(3)AR agonists (10(-12) to 10(-4) M) relaxed the smooth muscle in a concentration-dependent manner to the same extent in strips with and without the urothelium.


CONCLUSIONS
In addition to their presence in bladder smooth muscle, β(3)ARs are present in the urothelium where their activation may alter reflex voiding via release of factor(s) that act on non-myocyte structures including the afferent and/or efferent nerves to influence bladder contractility.
Department of Pharmacology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA. aura.kullmann@urogenix.com
F Aura
FA
Kullmann
Thomas R
TR
Downs
Debra E
DE
Artim
Brian J
BJ
Limberg
Mansi
M
Shah
Dan
D
Contract
William C
WC
de Groat
Jan S
JS
Rosenbaum
D000085:Acetates / Q000494:pharmacology; D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000818:Animals; D004983:Ethanolamines / Q000494:pharmacology; D005260:Female; D007150:Immunohistochemistry; D007211:Indoles / Q000494:pharmacology; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D011943:Receptors, Adrenergic, beta / Q000378:metabolism; D022702:Receptors, Adrenergic, beta-3 / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D001743:Urinary Bladder / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D014554:Urination / Q000187:drug effects; D019459:Urothelium / Q000187:drug effects / Q000378:metabolism*
C418363:((3-((2R)-(((2R)-3-chlorophenyl)-2-hydroxyethyl)amino)propyl)-1H-indol-7-yloxy)acetic acid; D000085:Acetates; D000318:Adrenergic beta-Agonists; D004983:Ethanolamines; D007211:Indoles; D012333:RNA, Messenger; D011943:Receptors, Adrenergic, beta; D022702:Receptors, Adrenergic, beta-3; C057368:BRL 37344