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Updated: Jun 5, 2026

Bladder Smooth Muscle Strip Contractility as a Method to Evaluate Lower Urinary Tract Pharmacology
Published on: August 18, 2014
Characterization of α1-adrenoceptor subtypes mediating contraction in human isolated ureters
Shoichi Sasaki1, Yoshitaka Tomiyama, Shinya Kobayashi
1Department of Nephro-urology, Nagoya City University Graduate School of Medical Sciences, Nagoya, Aichi, Japan. ssk@med.nagoya-cu.ac.jp
Objectives:
To characterize the contractile functions of the α(1)-adrenoceptor (AR) subtypes present in the human ureter.
Methods:
Specimens were taken from patients with renal cancer ("upper ureters;" n = 51) or bladder cancer ("lower ureters;" n = 23) who had not been treated by chemotherapy, radiation therapy, or immunotherapy before surgery. Patients systemically taking an α(1)-AR agonist or antagonist were excluded from this study. The effects of α(1)-AR antagonists against phenylephrine (α(1)-AR agonist)-induced contractions were evaluated in human isolated ureteral preparations.
Results:
Pooled data from all ureters showed that phenylephrine (α(1)-AR agonist) induced a concentration-dependent tonic contraction (pD(2) value, 4.92 ± 011). The phenylephrine-induced maximum contraction was significantly greater in lower ureters than in upper ones. Prazosin (nonselective α(1)-AR antagonist), silodosin (selective α(1A)-AR antagonist), and BMY-7378 (selective α(1D)-AR antagonist) all shifted the concentration-contractile response curve for phenylephrine to the right, the rank order of potencies in all ureters (pK(B) values) being silodosin (9.72 ± 0.14) > prazosin (8.64 ± 0.08) > BMY-7378 (7.04 ± 0.14). The α(1A)-AR antagonist silodosin was thus much more potent than the other 2 antagonists.
Conclusions:
Our results suggest that among α(1)-ARs, the α(1A) subtype plays the major role in contraction in the human ureter.
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