Expression of beta3-adrenoceptors in rat detrusor smooth muscle.
OBJECTIVE
To investigate the expression of beta-adrenoceptor (AR) subtypes responsible for detrusor smooth muscle relaxation.


METHODS
Isolated rat detrusor smooth muscle was examined by tension measurement and reverse transcription polymerase chain reaction (RT-PCR).


RESULTS
Norepinephrine (NE), epinephrine (EP) and isoproterenol (ISO) were found to relax the detrusor muscle pre-contracted by 6 x 10(-7) M carbachol in the presence of 10(-6) M phentolamine. NE relaxed the detrusor muscle as potently as EP. This potency order (NE=EP) thus indicated the beta-ARs of the rat detrusor muscle to possibly be a beta1 subtype. However, in the presence of 10(-6) M propranolol, beta1- and beta2- but not beta3-AR antagonist, NE showed a more potent relaxation than EP. This observation indicated that the rat detrusor muscle also possesses beta3-AR. RT-PCR revealed all three subtypes of beta-AR mRNA, namely beta1-, beta2- and beta3-AR mRNA, to be expressed in rat detrusor smooth muscle cells.


CONCLUSIONS
We concluded that beta3-ARs exist in rat detrusor smooth muscle based on both pharmacological and molecular biological studies. Based on these findings, beta-ARs of rat detrusor smooth muscle are considered to be mixed populations consisting of three subtypes which play an important role in relaxing smooth muscle in response to catecholamines.
Seguchi
H
H
Division of Molecular Cardiology, Research Institute of Angiocardiology, Faculty of Medicine, Kyushu University, Fukuoka, Japan.
Nishimura
J
J
Zhou
Y
Y
Niiro
N
N
Kumazawa
J
J
Kanaide
H
H
D000818:Animals; D004837:Epinephrine / Q000494:pharmacology; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D009126:Muscle Relaxation / Q000187:drug effects / Q000502:physiology*; D009130:Muscle, Smooth / Q000502:physiology*; D009638:Norepinephrine / Q000494:pharmacology; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D011943:Receptors, Adrenergic, beta / Q000302:isolation & purification / Q000378:metabolism*; D022702:Receptors, Adrenergic, beta-3; D013566:Sympathomimetics / Q000494:pharmacology; D001743:Urinary Bladder / Q000502:physiology
D012333:RNA, Messenger; D011943:Receptors, Adrenergic, beta; D022702:Receptors, Adrenergic, beta-3; D013566:Sympathomimetics; D007545:Isoproterenol; D009638:Norepinephrine; D004837:Epinephrine