Abstract
Introduction: Tamsulosin is used in the treatment of bladder outlet obstruction caused by benign prostatic hyperplasia in males. However, it has also been found to be beneficial in the treatment of overactive bladder in both men and women, although the mechanism of this action is unclear. One possible explanation could be an effect on the blood vessels supplying the bladder, where tamsulosin could potentially prevent sympathetic vasoconstriction and enhance bladder blood flow. Indeed, in recent years a number of studies have suggested
that lower urinary tract dysfunction, such as overactive bladder, may be caused by reduced blood flow. The objective of this study was to examine the α1-adrenoceptors involved in contraction of the blood vessels supplying to a pig bladder (a good model of the human bladder) and investigate whether tamsulosin and silodosin at clinical doses could influence blood flow to these tissues.
Materials & methods: Superior vesical artery branches from pig bladders (6-month old) were obtained from a local abattoir. Sections of artery (~4mm length, ~1mm internal diameter) were isolated and mounted between two horizontal stirrups under physiological conditions (in aerated Krebs-bicarbonate solution at 37˚C). Contractions of the circular muscle of the arteries was recorded in response to phenylephrine, a drug that acts at α1- adrenoceptors. Different subtypes of α1-adrenoceptors exist; however, in this study they were identified using selective antagonists for α1a-adrenoceptors (RS100329) and α1d- drenoceptors (BMY7378). The effects of the α1-adrenoceptor antagonist drugs tamsulosin and silodosin were also investigated.
Results: The α1d-adrenoceptor antagonist BMY7378 did not affect contractions of arteries to phenylephrine. However, the α1a-adrenoceptor antagonist
S100329 did significantly antagonise contractions to phenylephrine.
Both antagonists, tamsulosin and silodosin, significantly antagonised contractions of arteries to phenylephrine, at low doses (Fig. 1). None of the antagonists significantly affected maximal contractions to phenylephrine.
Conclusion: The results indicate that the arteries supplying blood to the bladder express the same α1- adrenoceptor subtype as those causing contraction of the human prostate. Both antagonists tamsulosin and silodosin antagonised the α1-adrenoceptor mediated vascular contractions at low doses. This suggests that these drugs will have significant effects on blood flow when given at doses used to treat benign prostatic hyperplasia and overactive bladder, and that changes in blood flow may indeed contribute to their clinical effectiveness
Original language | English |
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Pages (from-to) | 98-99 |
Number of pages | 2 |
Journal | Australian and New Zealand Continence Journal |
Volume | 25 |
Issue number | 4 |
Publication status | Published - 2019 |
Event | 28th National Conference on Incontinence - Pullman Melbourne Albert Park, Melbourne, Australia Duration: 13 Nov 2019 → 16 Nov 2019 Conference number: 28th https://www.ncoi.org.au/ |