Related Experiment Video
Updated: Aug 12, 2026

Bladder Smooth Muscle Strip Contractility as a Method to Evaluate Lower Urinary Tract Pharmacology
Published on: August 18, 2014
Partial bladder outlet obstruction induces urethral smooth muscle hypertrophy and decreased force generation
Joseph A Hypolite1, Shaohua Chang, Yongmu Zheng
1Division of Urology and Department of Pathobiology, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
Purpose:
PBOO leads to increased urinary frequency, decreased void volume, hypertrophy of the detrusor SM, and alterations in contractile and regulatory proteins. This study was done to determine whether PBOO induced increases in urinary frequency and detrusor SM hypertrophy are associated with an alteration in the contractility and expression of myosin isoforms in urethral SM.
Materials And Methods:
PBOO was surgically induced in male New Zealand White rabbits, and sham operated rabbits served as controls. After surgery, rabbits were kept 12 days, and prior to sacrifice, urine output and voiding frequency were monitored by keeping the animals in metabolic cages for 24 hours. Animals with increased urinary frequency (mean +/- SEM 43 +/- 12 voids per 24 hours) and sham operated rabbits (6 +/- 3 voids per 24 hours) were used for this study. Morphology of the urethra was studied using light and immunofluorescence microscopy. The expression of myosin isoforms was analyzed at the mRNA and protein levels by RT-PCR and Western blotting.
Results:
The urethral wall and SM of PBOO rabbits showed hypertrophy. The force produced by the longitudinal muscle strips of PBOO animals in response to phenylephrine, KCl, or electrical field stimulation was decreased 50%, 37% and 40%, respectively. Immunofluorescence microscopy revealed a decrease in nerve density. RT-PCR and Western blotting showed a decrease in the expression of myosin isoform SM-B with a concomitant increase in SM-A at the mRNA and protein levels.
Conclusions:
Our data show hypertrophy of the urethral wall and SM, and alterations in contraction, innervation, and myosin isoforms in PBOO induced detrusor hypertrophy.
Related Concept Videos
Smooth Muscle Contraction
The onset of contraction is triggered by an increase in calcium ions within the sarcoplasm, similar to the process in striated muscle. However, smooth muscles have a relatively smaller reservoir of the sarcoplasmic...
Urinary Bladder
In males, the bladder is situated in front of the rectum, while in females, it is positioned anterior to the vagina and uterus. The bladder floor contains an inverted triangular area called the trigone, defined by the two ureteric...
The Micturition Reflex
The process begins with bladder filling, where the bladder wall stretches as urine accumulates. This stretching activates the urine storage reflex, mediated by the sacral spinal segments and the pontine storage center. Efferent sympathetic impulses stimulate the detrusor muscle to relax and the internal urethral sphincter to contract, facilitating urine...
Anatomy of the Genitourinary System II: Bladder and Urethra
Urodynamic Studies: Uroflowmetry
Microbiota of the Urogenital Tract

