Inhibition by tamsulosin of tension responses of human hyperplastic prostate to electrical field stimulation

• Published in: European journal of pharmacology 1996-06, Vol.305 (1), p.177-180
• Main Authors: Chueh, Shih-Chieh, Guh, Jih-Hwa, Chen, Jun, Lai, Ming-Kuen, Ko, Feng-Nien, Teng, Che-Ming
• Format: Article
• Language: English
• Subjects: Adrenergic alpha-Agonists - pharmacology; Adrenergic alpha-Antagonists - pharmacology; Aged; Biological and medical sciences; Calcium Channel Blockers - pharmacology; Electric Stimulation; Electrical field stimulation; Humans; In Vitro Techniques; Male; Medical sciences; Middle Aged; Muscle Contraction - drug effects; Muscle, Smooth - drug effects; Muscle, Smooth - physiopathology; Nifedipine - pharmacology; Norepinephrine - metabolism; Pharmacology. Drug treatments; Phenylephrine - pharmacology; Potassium - pharmacology; Prazosin - pharmacology; Prostate - drug effects; Prostate - metabolism; Prostate - physiopathology; Prostate, human; Prostatic Hyperplasia - metabolism; Prostatic Hyperplasia - physiopathology; Sulfonamides - pharmacology; Tamsulosin; Urinary system; α1-Adrenoceptor stimulation
• ISSN: 0014-2999; 1879-0712
• DOI: 10.1016/0014-2999(96)00197-5

Tamsulosin (10 −10−10 −9 M) or prazosin (10 −9−10 −8 M) concentration dependently blocked the tension responses to electrical field stimulation (0.3 ms duration, 80 V and 20 Hz) in human hyperplastic prostate with IC 50 values of (1.93 ± 0.26) × 10 −10 M and (2.11 ± 0.21) × 10 −9 M, respectively. The relative potency of tamsulosin with reference to prazosin was 10.96. The p A 2 values for tamsulosin and prazosin against phenylephrine-induced contractions were 10.05 ± 0.16 and 9.25 ± 0.07, respectively. The relative potency of tamsulosin with reference to prazosin was 6.31. In the presence of prazosin to block α 1-adrenoceptor-mediated responses, nifedipine (10 −5 M), but not tamsulosin (10 −9 M), significantly blocked the tension responses in human hyperplastic prostate induced by increasing [Ca 2+] o concentrations (10 −4 to 3 × 10 −3 M) in a Ca 2+-free environment pre-depolarized with 60 mM K +. Additionally, the effects of prazosin and tamsulosin on electrical field stimulation-evoked [ 3H]noradrenaline release were studied on the S 3 S 2 ratios. It appeared that both drugs had little effect on this release reaction, with S 3 S 2 ratios of 0.96 ± 0.02 and 0.90 ± 0.02, respectively. These results indicate that tamsulosin is a potent antagonist against endogenous sympathetic stimulation in human hyperplastic prostate.