Contractile properties of urethral smooth muscles of young and aged female dogs: morphological and pharmacological aspects

Int J Urol. 2000 Aug;7(8):298-306. doi: 10.1046/j.1442-2042.2000.00198.x.

Abstract

Background: Alpha1-adrenoceptors are highly concentrated in the urethral smooth muscles and may play an important role in the contraction of this area. However, detailed examinations of age-related changes of the properties of urethral smooth muscle have rarely been undertaken.

Methods: The contractile properties of urethras from young non-parous and old parous female beagles were determined with a urethral function study, macroscopic autoradiography for urethras using [3H]-labeled tamsulosin and morphometry of the urethral muscles.

Results: The antagonistic effect (pA2) of prazosin for norepinephrine was 7.76+/-0.13 in young dogs and 7.62+/-0.06 in aged dogs. The specific binding of [3H]-tamsulosin (a relatively selective alpha1A-adrenoceptor antagonist) was recognized diffusely in proximal urethras with in vitro autoradiography. The density of binding in smooth muscles was approximately 60 and 40% in circular longitudinal layers, respectively, for both dogs.

Conclusions: The female canine urethra had alpha1A, and alpha1L-adrenoceptors. No age-related changes were seen in the function of the proximal urethra, distribution of alpha1-adrenoceptor binding sites and smooth muscle densities.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adrenergic alpha-Agonists / pharmacology
  • Adrenergic alpha-Antagonists / metabolism
  • Adrenergic alpha-Antagonists / pharmacology
  • Aging / physiology*
  • Animals
  • Autoradiography
  • Dogs
  • Female
  • Muscle Contraction*
  • Muscle, Smooth / anatomy & histology
  • Muscle, Smooth / drug effects
  • Muscle, Smooth / metabolism
  • Muscle, Smooth / physiology*
  • Norepinephrine / pharmacology
  • Phenylephrine / pharmacology
  • Prazosin / pharmacology
  • Sulfonamides / metabolism
  • Tamsulosin
  • Urethra / anatomy & histology
  • Urethra / drug effects
  • Urethra / metabolism
  • Urethra / physiology*

Substances

  • Adrenergic alpha-Agonists
  • Adrenergic alpha-Antagonists
  • Sulfonamides
  • Phenylephrine
  • Tamsulosin
  • Norepinephrine
  • Prazosin