Contractile properties of urethral smooth muscles of young and aged female dogs: morphological and pharmacological aspects.
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.
Ahmed
H
H
Department of Urology, Faculty of Medicine, The University of Tokyo, Japan.
Moriyama
N
N
Fukasawa
R
R
Nishimatsu
H
H
Tanaka
Y
Y
Kitamura
T
T
Tatemichi
S
S
Akiyama
K
K
Suzuki
Y
Y
Aisaka
K
K
D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000317:Adrenergic alpha-Antagonists / Q000378:metabolism / Q000494:pharmacology; D000375:Aging / Q000502:physiology*; D000818:Animals; D001345:Autoradiography; D004285:Dogs; D005260:Female; D009119:Muscle Contraction; D009130:Muscle, Smooth / Q000033:anatomy & histology / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D009638:Norepinephrine / Q000494:pharmacology; D010656:Phenylephrine / Q000494:pharmacology; D011224:Prazosin / Q000494:pharmacology; D013449:Sulfonamides / Q000378:metabolism; D000077409:Tamsulosin; D014521:Urethra / Q000033:anatomy & histology / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*
D000316:Adrenergic alpha-Agonists; D000317:Adrenergic alpha-Antagonists; D013449:Sulfonamides; D010656:Phenylephrine; D000077409:Tamsulosin; D009638:Norepinephrine; D011224:Prazosin