In vivo Properties of the Urinary Bladder Wall and their Modulation by Estradiol and Raloxifene in a Rat Model

Abstract

Objectives: Urinary incontinence is a common symptom of urogenital aging that affects a considerable proportion of postmenopausal women. Morphological and morphometrical modulation of the bladder by estrogen are known. Yet data showing that this translates into changes of in vivo function of the urinary bladder are missing.

Methods: We measured urodynamic parameters in anaesthetized, surviving rats. Following ovariectomy animals were divided into three groups and fed either an estradiol-, raloxifene-, or unsupplemented soy-free formula for ten weeks. Via a transurethral catheter the intravesical pressure was recorded during a stretch period (the urinary bladder was filled), and a one-minute isometric accommodation period immediately after the filling period. Upon termination of the experiment upper and lower halves of the bladder were processed histologically.

Results: The estrogen-, and raloxifene-treated animals showed significantly higher pressures in responses to rapid stretch. Bladder compliance during the isometric period on the other hand was not significantly affected by these treatments. Thickness of the epithelial layer, collagen content and muscle bundles were significantly increased by estrogen and raloxifene treatment.

Conclusions: This is a good animal model to investigate modulation of detrusor muscle contractility and stiffness. Both estradiol and raloxifene increase bladder contractility. Urinary bladder morphology indicates that estrogen acts primarily in the upper half of this organ since significant effects on collagen content and muscle fibers are only found in this part.

Key words

Urinary bladder wall - transurethral catheter - intravesical pressure - estradiol - raloxifene

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