EXPRESSION OF beta 3-ADRENOCEPTORS IN RAT DETRUSOR SMOOTH MUSCLE

AbstractPurpose: To investigate the expression of beta-adrenoceptor (AR) subtypes responsible for detrusor smooth muscle relaxation.Materials and 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 × 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 [equals, falling dots] EP) thus indicated the beta-ARs of the rat detrusor muscle to possibly be a beta 1 subtype. However, in the presence of 10−6 M propranolol, beta 1- and beta 2- but not beta 3-AR antagonist, NE showed a more potent relaxation than EP. This observation indicated that the rat detrusor muscle also possesses beta 3-AR. RT-PCR revealed all three subtypes of beta-AR mRNA, namely beta 1-, beta 2- and beta 3-AR mRNA, to be expressed in rat detrusor sm...