Effects of tamsulosin on bladder blood flow and bladder function in rats with bladder outlet obstruction.
OBJECTIVE
To investigate the mechanism underlying the ameliorating effect of tamsulosin, an alpha(1)-adrenoceptor antagonist, on storage symptoms associated with benign prostatic hyperplasia, the effects of tamsulosin on bladder blood flow (BBF) and bladder function was evaluated in rats with bladder outlet obstruction (BOO).


METHODS
BOO was produced by partial ligature of the proximal urethra, which was maintained for 2 weeks. Tamsulosin was subcutaneously administered via an osmotic pump for 2 weeks immediately after the BOO surgery. The BBF in the sham-operated rats, the control BOO rats, and the tamsulosin-treated BOO rats was measured using the fluoromicrosphere method. Each rat was kept in a metabolic cage for observation of micturition behavior. Expression of the alpha(1)-adrenoceptor subtype mRNA in the vesical artery was measured by reverse transcriptase-polymerase chain reaction.


RESULTS
BBF was significantly reduced in BOO rats compared with sham-operated rats, and tamsulosin significantly increased the BBF in BOO rats. Tamsulosin ameliorated the decrease in mean voided volume in BOO rats with bladder masses < 500 mg. Expression of the alpha(1)-adrenoceptor subtype in the vesical artery was alpha(1a)- > alpha(1d)-adrenoceptors; almost no expression was observed of alpha(1b)-adrenoceptors in either sham-operated or BOO rats.


CONCLUSIONS
Tamsulosin increased BBF in BOO rats via an antagonistic effect, presumably on the alpha(1A)- and/or alpha(1D)-adrenoceptor in the vesical artery mainly, and improved the decrease in mean voided volume. Therefore, the results of this study suggest that tamsulosin improves bladder overactivity via improvement of BBF.
Okutsu
Hiroko
H
Applied Pharmacology Research Laboratories, Astellas Pharma Inc, Miyukigaoka, Tsukuba-shi, Ibaraki, Japan.
Matsumoto
Seiji
S
Hanai
Tadashi
T
Noguchi
Yukiko
Y
Fujiyasu
Noriko
N
Ohtake
Akiyoshi
A
Suzuki
Masanori
M
Sato
Shuichi
S
Sasamata
Masao
M
Uemura
Hirotsugu
H
Kurita
Takashi
T
D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology*; D000818:Animals; D005260:Female; D051381:Rats; D017208:Rats, Wistar; D012039:Regional Blood Flow / Q000187:drug effects*; D013449:Sulfonamides / Q000494:pharmacology*; D000077409:Tamsulosin; D001743:Urinary Bladder / Q000098:blood supply* / Q000187:drug effects*; D001748:Urinary Bladder Neck Obstruction / Q000503:physiopathology*
D000317:Adrenergic alpha-Antagonists; D013449:Sulfonamides; D000077409:Tamsulosin