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Updated: Sep 17, 2026

Bladder Smooth Muscle Strip Contractility as a Method to Evaluate Lower Urinary Tract Pharmacology
Published on: August 18, 2014
Chloride-dependent mechanisms contribute to urinary bladder smooth muscle contractility: Pharmacological and
Yuh-Chen Kuo1,2,3, Vincent F S Tsai2,4,5, Shih-Ping Liu2
1Department of Urology, Yangming Branch of Taipei City Hospital, Taipei, Taiwan.
Objectives:
To investigate the functional role of chloride-dependent signaling pathways in urinary bladder smooth muscle (SM) contractility and to evaluate the expression of ClC-3 and CLCA4 in rat bladder tissue.
Materials And Methods:
Expression of ClC-3 and CLCA4 in rat bladder tissue was examined using Western blotting and immunohistochemistry. Functional studies were conducted using isolated bladder SM strips (2 mm × 2 mm × 10 mm) from adult male Wistar rats mounted in organ bath chambers for isometric tension recording. Potassium chloride (KCl)-induced contractions were assessed under varying extracellular chloride concentrations (138-8 mM) and after substitution with Br- or I- . Norepinephrine (NE)-induced contractions were evaluated with pretreatment of chloride transport inhibitors (bumetanide, HEPES without bicarbonate, and ethacrynic acid) and chloride channel blockers (4,4'-diisothiocyano-2,2'-stilbene-disulfonic acid, anthracene-9-carboxylic acid, and niflumic acid) at different concentrations.
Results:
ClC-3 and CLCA4 were expressed in both urothelial and SM layers. Reduction of extracellular chloride concentration significantly attenuated KCl-induced contractions in a concentration-dependent manner (P < 0.01) and substitution with bromide or iodide produced similar effects. Chloride transport inhibitors and channel blockers significantly and dose-dependently suppressed NE-induced contractions (all P < 0.01). The inhibitory effects were consistently observed across multiple pharmacological interventions.
Conclusion:
The present study provides pharmacological and molecular evidence supporting a contributory role of chloride-dependent signaling in bladder SM contractility under ex vivo conditions. Expression of ClC-3 and CLCA4 in urothelial and SM layers further suggests that chloride-dependent regulation may involve multiple bladder compartments. Although the precise molecular mechanisms remain incompletely defined, these findings support further investigation into chloride-dependent signaling pathways in bladder physiology and dysfunction.
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