INCREASED CONTRACTILE RESPONSE TO PHENYLEPHRINE IN DETRUSOR OF PATIENTS WITH BLADDER OUTLET OBSTRUCTION: EFFECT OF THE α1A AND α1D-ADRENERGIC RECEPTOR ANTAGONIST TAMSULOSIN

Publisher Website
Google Scholar
Abstract
Purpose: α1-Adrenergic receptor (α1-AR) antagonists are effective for treating patients with lower urinary tract symptoms associated with bladder outlet obstruction (BOO). In humans up-regulation of α1-AR function in the detrusor in patients with BOO has been suggested but to our knowledge it is not yet confirmed. We investigated the effect of phenylephrine, an α1-AR agonist, on isometric tension in small detrusor muscle biopsies from patients with lower urinary tract symptoms and BOO compared with controls. Materials and Methods: Detrusor biopsies were obtained from 7 men with BOO undergoing prostatectomy and 7 undergoing cystectomy for bladder cancer (controls). Patients were characterized by symptom score and urodynamics. Isometric tension was measured in detrusor biopsies with an especially built mini myograph. Results: Mean International Prostate Symptom Score ± SEM in patients with BOO and controls were 22.3 ± 2.3 and 4.0 ± 0.8, respectively. Phenylephrine (10−6 to 10−3 M) induced a significant contractile response increase in detrusor biopsies from patients with BOO compared with controls at all concentrations. Tamsulosin (0.1 to 3.0 nM) inhibited phenylephrine induced contraction in a dose dependent manner. Conclusions: To our knowledge this functional study shows for the first time a highly significant increase in contractile force to phenylephrine in patients with BOO compared with controls. These results suggest up-regulation of α1-AR function in BOO since contractile responses were potently inhibited by the α1A/D-AR antagonist tamsulosin.