Abstract

The purpose of the present study was to confirm the presence of β₃-adrenoceptor subtype in the relaxation of human urinary bladder detrusor tissue by reverse transcription-polymerase chain reaction (PCR); direct sequencing of the PCR product, in situ hybridization; and isometric contraction. Using reverse transcription-PCR, the mRNAs of three receptor subtypes (β₁, β₂, and β₃) were expressed in the human urinary bladder detrusor tissue. Direct sequencing of the PCR product of the above β₃-adrenoceptor revealed no mutation in the amplified regions. In situ hybridization with digoxygenin-labeled oligonucleotide probe revealed the presence of the mRNA of β₃-adrenoceptor subtype in the smooth muscle of the urinary bladder. The relaxant effects of isoproterenol (a nonselective β-adrenoceptor agonist); ZD7114, BRL37344, and CGP12177A (putative selective β₃-adrenoceptor agonists); and SR59230A (a putative selective β₃-adrenoceptor antagonist) were tested using an isometric contraction technique. Isoproterenol in either the presence or absence of both atenolol (a β₁-adrenoceptor-selective antagonist) and butoxamine (a β₂-adrenoceptor-selective antagonist) revealed a relaxant effect on the carbachol-induced contraction of the human urinary bladder detrusor. Both BRL37344 and CGP12177A also revealed relaxant effects on the human urinary bladder detrusor, but ZD7114 did not elicit any relaxation. These results suggest that β₃-adrenoceptor may have some role in urine storage in the human urinary bladder.