Document Detail

The effects of tamsulosin, a high affinity antagonist at functional alpha 1A- and alpha 1D-adrenoceptor subtypes.
MedLine Citation:
PMID:  9117115     Owner:  NLM     Status:  MEDLINE    
1. The actions of the alpha 1-adrenoceptor antagonist tamsulosin have been examined at functional alpha 1-adrenoceptor subtypes and compared with those at the human prostate receptor. 2. At the alpha 1D-adrenoceptors of the rat aorta, tamsulosin acted as a competitive antagonist with a high affinity (pKB = 10.1). 3. At the alpha 1B-adrenoceptor of the rat spleen and rabbit corpus cavernosum penis, tamsulosin again acted as a competitive antagonist but with a significantly lower affinity (pKB = 8.9-9.2). 4. Tamsulosin acted as an unsurmountable antagonist of the alpha 1A-adrenoceptor-mediated responses of the rat and human vas deferens, reducing maximal responses to phenylephrine by 20% and 50%, respectively, at an antagonist concentration of 1 nM. Responses of depolarized (100 mM KCl) rat vas deferens preparations were unaffected by 10 nM tamsulosin but this concentration reduced maximal responses to 5-hydroxytryptamine (5-HT) in this tissue. 5. When longer antagonist incubation periods (> or = 60 min) were used, tamsulosin behaved as a competitive antagonist on the human prostate with a significantly higher affinity (pKB = 10.0) than obtained at the alpha 1B-adrenoceptor. 6. The data demonstrate that tamsulosin is a high affinity antagonist at functional alpha 1-adrenoceptors with a selectivity alpha 1D > or = alpha 1A > alpha 1B. In some tissues the compound exhibits an additional unsurmountable antagonist action, the clinical significance of which is unknown.
A J Noble; R Chess-Williams; C Couldwell; K Furukawa; T Uchyiuma; C Korstanje; C R Chapple
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Publication Detail:
Type:  In Vitro; Journal Article    
Journal Detail:
Title:  British journal of pharmacology     Volume:  120     ISSN:  0007-1188     ISO Abbreviation:  Br. J. Pharmacol.     Publication Date:  1997 Jan 
Date Detail:
Created Date:  1997-04-18     Completed Date:  1997-04-18     Revised Date:  2008-11-20    
Medline Journal Info:
Nlm Unique ID:  7502536     Medline TA:  Br J Pharmacol     Country:  ENGLAND    
Other Details:
Languages:  eng     Pagination:  231-8     Citation Subset:  IM    
Department of Biomedical Science, Western Bank, University of Sheffield, U.K.
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MeSH Terms
Adrenergic alpha-Antagonists / pharmacology*
Dose-Response Relationship, Drug
Middle Aged
Prostate / drug effects
Rats, Wistar
Receptors, Adrenergic, alpha-1 / antagonists & inhibitors*
Sulfonamides / pharmacology*
Vas Deferens / drug effects,  physiology
Reg. No./Substance:
0/Adrenergic alpha-Antagonists; 0/Receptors, Adrenergic, alpha-1; 0/Sulfonamides; 106133-20-4/tamsulosin

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