The aim of this study was to characterize endothelin receptor subtypes of the detrusor muscle of the human urinary bladder. The receptor subtypes mediating endothelin (ET)-1-induced activity in the human detrusor smooth muscles have been characterized using isometric contraction and reverse transcription–polymerase chain reaction (RT–PCR). ET-1 (a non-selective ET receptor agonist; 10-10 M to 10-6 M) exhibited concentration-dependent contractions in human urinary bladder with a plateau at concentrations above 3×10-7 M. Neither IRL1620 nor sarafotoxin S6c (both ETB-selective agonists; 10-10 M to 10-6 M) elicited contractile activity in the human urinary bladder detrusor smooth muscle. FR139317 (an ETA-selective antagonist; 10-7 M to 10-5 M) produced a marked shift to the right of the ET-1 concentration–response curve in human urinary bladder detrusor smooth muscle (from the Schild plot TpA2 = 7.96; slope = 0.95). In contrast, RES701-1 (an ETB-selective antagonist; 10-7 M to 10-5 M) had no effect on the ET-1 concentration–response curve. RT–PCR revealed positive amplification of ETA receptor mRNA fragment, but not ETB. These results indicate that the ET-1-induced contractile effects of urinary bladder detrusor smooth muscle seem to be mediated mainly by the ETA receptor, not by the ETB receptor.

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