Alpha1-adrenergic receptor subtypes in human detrusor.
OBJECTIVE
To identify and quantitate alpha1-adrenergic receptor (alpha1AR) subtype expression in human detrusor.


METHODS
Initial studies to determine alpha1AR expression in human detrusor were performed using saturation binding with [125I]HEAT. Once the presence of alpha1ARs was documented, subtype (alpha1a, alpha1b, alpha1d) expression at the mRNA level (and comparison with rat) was determined with RNase protection assays (human detrusor) and RT-PCR (human detrusor, rat whole bladder). Competition binding analysis with the alpha1dAR-selective ligand BMY7378 was used to measure alpha1AR subtype expression at a protein level in human detrusor.


RESULTS
Alpha1AR expression in human detrusor was low but reproducible (6.3 +/- 1.0 fmol./mg. total protein). RNase protection assays performed on total RNA extracted from human detrusor revealed the following alpha1AR subtype expression: alpha1d (66%) > alpha1a (34%), and no alpha1b. RT-PCR confirmed alpha1AR subtype mRNA distribution in human detrusor with alpha1d (approximately 60-70%) > alpha1a (approximately 30-40%), and a lack of alpha1b mRNA. Rat whole bladder expressed different alpha1AR subtype mRNA than human detrusor, with alpha1a approximately alpha1b approximately alpha1d. The presence of alpha1d > alpha1a expression in human detrusor was confirmed at a protein level by competition analysis utilizing BMY7378 which revealed a two-site fit, with Ki and high affinity binding (66%) consistent with the alpha1dAR subtype.


CONCLUSIONS
Human detrusor contained two alpha1AR subtypes (alpha1d > alpha1a), a finding that is different from rat, another commonly used animal model. Since non-subtype selective alpha1AR antagonists ameliorate irritative bladder symptoms (in men and women with/without outlet obstruction), and Rec 15/2739 (alpha1a selective antagonist) does not improve symptom scores in BPH, our findings suggest bladder alpha1dARs may provide a potentially novel mechanism underlying these therapeutic benefits.
Malloy
B J
BJ
Department of Surgery, Duke University Medical Center, Durham, North Carolina 27710, USA.
Price
D T
DT
Price
R R
RR
Bienstock
A M
AM
Dole
M K
MK
Funk
B L
BL
Rudner
X L
XL
Richardson
C D
CD
Donatucci
C F
CF
Schwinn
D A
DA
D000818:Animals; D006801:Humans; D008297:Male; D009130:Muscle, Smooth / Q000737:chemistry*; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D018340:Receptors, Adrenergic, alpha-1 / Q000032:analysis* / Q000145:classification / Q000235:genetics; D001743:Urinary Bladder / Q000737:chemistry*
D012333:RNA, Messenger; D018340:Receptors, Adrenergic, alpha-1