Yoshitaka Tomiyama

EXISTENCE OF A β3-ADRENOCEPTOR AND ITS FUNCTIONAL ROLE IN THE HUMAN URETER

Purpose: We tried to determine the β-adrenoceptor (AR) subtypes distributed in the human ureter and to clarify their functional role in ureteral relaxation.Materials and Methods: 1) Effects of β-AR agonists on either spontaneous or KCl-induced contractions of the human ureter and the antagonism by β-AR antagonists on isoprenaline (a non-selective β-AR agonist)-induced effects were evaluated in vitro. 2) Displacement by β-AR antagonists of [3H]-dihydroalprenolol binding to a membrane preparation derived from human ureteral smooth muscle was evaluated. 3) A reverse transcription polymerase chain reaction assay was performed to determine the expression of the mRNA for β1-, β2- and β3-ARs in human ureteral smooth muscle.Results: 1) Isoprenaline and procaterol (a β2-AR agonist) concentration-dependently suppressed both spontaneous and KCl-induced contractions of the human ureter. The β3-AR agonists, CGP-12177A and CL-316243, also suppressed these ureteral contractions, but dobutamine (a β1-AR agonist) had litt...

β-Adrenoceptor subtypes in the ureteral smooth muscle of rats, rabbits and dogs

Abstract We investigated the β-adrenoceptor subtypes mediating ureteral relaxation in rats, rabbits and dogs. The relaxing effects of β-adrenoceptor agonists were evaluated on KCl-induced ureteral contractions. The rank order of potency of the catecholamines tested was isoprenaline>noradrenaline>adrenaline in rat ureter; isoprenaline>adrenaline>noradrenaline in rabbit ureter; only isoprenaline was effective in canine tissues. The β1-adrenoceptor agonist, dobutamine, produced relaxation of rat ureter. The β2-adrenoceptor agonist, procaterol, produced more significant relaxation of rabbit ureter than did dobutamine. CL-316243 [(R,R)-5-[2-[[2-(3-chlorophenyl)-2-hydroxyethylamino]propyl]-1,3-benzodioxole-2,2-dicarboxylate] and CGP-12177A [(±)[4-[3[(1,1-dimethylethyl)amino]-2-hydroxypropoxy]-1,3-dihydro-2H-benzimidazol-2-one hydrochloride], β3-adrenoceptor agonists, were more effective in relaxing canine ureter than were dobutamine and procaterol. Isoprenaline-induced relaxation was antagonized by a β1-adrenoceptor antagonist, CGP-20712A [2-hydroxy-5(2-((2-hydroxy-3-(4-((1-methyl-4-trifluoromethyl)1H-imidazole-2-yl)phenoxy)propyl)amino)ethoxy)-benzamide monomethane sulphonate], in rats and by a β2-adrenoceptor antagonist, ICI-118,551 [(±)-1-[(2,3-dihydro-7-methyl-1H-inden-4-yl)oxy]-3-[(1-methylethyl)amino]-2-butanol hydrochloride], in rabbits. The non-selective β-adrenoceptor antagonist, bupranolol, antagonized isoprenaline-induced relaxation in all species tested. In conclusion, β-adrenoceptor agonists may relax ureter by stimulating mainly β1-adrenoceptors in rats, β2-adrenoceptors in rabbits and mainly β3-adrenoceptors in dogs.

Effects of silodosin and tamsulosin on the urethra and cardiovascular system in young and old dogs with benign prostatic hyperplasia

We examined whether the effects (efficacy on the urethra and hypotension) of silodosin (alpha(1A)-adrenoceptor antagonist) and tamsulosin (alpha(1A+1D)-adrenoceptor antagonist) in dogs with benign prostatic hyperplasia altered with age. We used young and old dogs, diagnosed as having benign prostatic hyperplasia by veterinarians palpation. Under anesthesia, the increase in intraurethral pressure evoked by hypogastric nerve stimulation was measured, together with the level of systemic mean blood pressure. Each drug was administered intravenously in progressively increasing doses. At the end of the experiment, the prostate was isolated from each dog, then weighed and investigated pathologically to confirm benign prostatic hyperplasia. The wet weight of the prostate was greater in old dogs with benign prostatic hyperplasia than in young dogs with benign prostatic hyperplasia. By light microscopy, hyperplasia in the prostatic epithelium was confirmed in both groups. Silodosin (0.3-300 microg/kg) dose-dependently inhibited the hypogastric nerve stimulation-induced increase in intraurethral pressure (without significant hypotensive effects) in both young and old dogs with benign prostatic hyperplasia. Tamsulosin (0.3-300 microg/kg) also dose-dependently inhibited the intraurethral pressure increase in both groups, but it had a hypotensive effect that was significantly greater in old than in young dogs with benign prostatic hyperplasia. In conclusion, as regards the effect of silodosin on intraurethral pressure, potency was similar between young and old dogs with benign prostatic hyperplasia, and it was without significant hypotensive effects. We therefore suggest that silodosin might be a good medication for lower urinary tract symptoms in patients with benign prostatic hyperplasia in all age groups.

EFFECTS OF ISOPROTERENOL AND BUTYLSCOPOLAMINE ON THE FRICTION BETWEEN AN ARTIFICIAL STONE AND THE INTRAURETERAL WALL IN ANESTHETIZED RABBITS

PURPOSE We evaluated the effects of the nonselective beta-adrenoceptor agonist isoproterenol and the nonselective muscarinic antagonist butylscopolamine on ureteral wall tension, namely friction between an artificial stone and the intraureteral wall, in anesthetized rabbits. MATERIALS AND METHODS The relaxing effect of the drugs on the KCl induced tonic contraction was examined in isolated rabbit ureters. The effect of the drugs on the applied force needed for the artificial stone to pass at a constant speed through the ureter, called sliding force, was evaluated in anesthetized rabbits. RESULTS In a concentration dependent manner isoproterenol but not butylscopolamine reduced the KCl induced contraction in isolated ureter (mean pD2 7.35 +/- 0.06). Intravenous administration of 1 and 10 microg./kg. isoproterenol significantly decreased the friction between the artificial stone and intraureteral wall in anesthetized rabbits with sliding force at 15 minutes after drug administration decreased by 54.5% and 63.6%, respectively. In contrast, 100 and 1,000 microg./kg. butylscopolamine intravenously had no evident effect on ureteral wall tension. CONCLUSIONS Our results strongly suggest that ureteral smooth muscle relaxation by beta-adrenergic stimulation reduces ureteral wall tension, thereby, diminishing mechanical effects impeding the movement of a ureteral stone down the ureter.

Mechanical Function and Gene Expression of α1-Adrenoceptor Subtypes in Dog Intravesical Ureter

OBJECTIVES To characterize the contractile functions and gene expression of the alpha(1)-adrenoceptor (AR) subtypes present in the dog intravesical ureter. METHODS In a functional study, alpha(1)-AR antagonists were evaluated against phenylephrine (alpha(1)-AR agonist)-induced contractions in dog isolated intravesical ureteral preparations. The quantitative expression of alpha(1)-AR subtype mRNA in this tissue was determined using real-time quantitative reverse transcriptase-polymerase chain reaction. RESULTS In the isolated intravesical ureter, prazosin (nonselective alpha(1)-AR antagonist), silodosin (selective alpha(1A)-AR antagonist), naftopidil (selective alpha(1D)-AR antagonist), and BMY-7378 (selective alpha(1D)-AR antagonist) all shifted the concentration-contractile response curve for phenylephrine to the right. The rank order of potencies (pK(B) value) was silodosin (9.45 +/- 0.14), prazosin (8.16 +/- 0.08), naftopidil (7.39 +/- 0.19), and BMY-7378 (6.78 +/- 0.20). The alpha(1A)-AR antagonist silodosin was much more potent than the 2 alpha(1D)-AR antagonists. The rank order of mRNA expression levels among the alpha(1)-AR subtypes was alpha(1d) (72.68%), alpha(1a) (24.14%), and alpha(1b) (3.18%). CONCLUSIONS In the dog intravesical ureter, alpha(1A)-AR plays a major role in contraction, despite the prevalence of alpha(1D)-AR.

EXPRESSION LEVEL AND ROLE IN URETERAL CONTRACTION OF ALPHA1-ADRENOCEPTOR SUBTYPES IN HUMAN URETER

Hypothesis / aims of study Recently there have been some reports that tamsulosin is effective for discharge of ureter stones. The relation between voiding function of the lower urinary tract and alpha1-adrenoceptor (AR) is well known, and is applied clinically. On the other hand, there has been little research into alpha1-AR of the upper urinary tract. We studied the expression and role in ureteral contraction of alpha1-AR subtypes, which was considered to clarify the mechanism of ureteral urodymanics and passing ureter stones.

Effect of silodosin on intraurethral pressure increase induced by hypogastric nerve stimulation in dogs with benign prostatic hyperplasia

We compared the urethral and cardiovascular effects of silodosin (selective alpha(1A)-adrenoceptor antagonist), a novel medication for benign prostatic hyperplasia (BPH), with those of tamsulosin (selective alpha(1A)/alpha(1D)-adrenoceptor antagonist) and naftopidil (selective alpha(1D)-adrenoceptor antagonist). We evaluated the effects of these three drugs on the increase in intraurethral pressure (IUP) induced by electrical stimulation of the hypogastric nerve in anesthetized dogs with spontaneous BPH. All three drugs dose-dependently reduced both the increase in IUP and the mean blood pressure (MBP). The rank order of potencies was tamsulosin>silodosin>naftopidil for the reductions in both IUP and MBP. However, the uroselectivity (ED(15) value for hypotensive effect/ID(50) value for reduction in IUP) of silodosin (uroselectivity, 19.8) was about 21 and 4 times higher than that of tamsulosin (0.939) and naftopidil (4.94), respectively. These data suggest that silodosin might be one of the most useful medications for dysuria in BPH patients.

Comparison between CL-316243- and CGP-12177A-Induced Relaxations in Isolated Canine Ureter

We compared the effects of CL-316243, a selective β3-adrenoceptor agonist, and CGP-12177A, a nonconventional partial β-adrenoceptor agonist, on the KCl-induced contraction in the isolated canine ureter. CL-316243 concentration dependently relaxed the ureteral contraction, the pD2 value being 7.75 ± 0.11. This relaxation was competitively antagonized by the selective β3-adrenoceptor antagonist SR58894A and by the nonselective β-adrenoceptor antagonist bupranolol, their pA2 values being 7.08 ± 0.08 and 6.43 ± 0.09, respectively. CGP-12177A concentration dependently reduced the KCl-induced contraction, the pD2 value being 6.30 ± 0.25. Even at 1 × 10–5 mol/l, CGP-20712A (a selective β1- adrenoceptor antagonist) did not shift the concentration-response curves for CL-316243 or CGP-12177A. SR58894A did not induce a parallel rightward shift in the concentration-response curve for CGP-12177A, but bupranolol did produce such a shift, pA2 and slope values in the Schild plot being 7.15 ± 0.77 and 0.60 ± 0.15, respectively. Hence, the competition characteristics for SR58894A and bupranolol differed between the CL- 316243-induced and CGP-12177A-induced relaxations. Our results suggest that CGP-12177A produces ureteral relaxation in the dog via an atypical β-adrenoceptor (possibly, an atypical site/state of the β3-adrenoceptor) as well as via the typical β3-adrenoceptor.

Ureteral Selectivity of Intravenous β-Adrenoceptor Agonists in Pig Model of Acute Ureteral Obstruction: Comparison of KUL-7211, a Selective β2/β3 Agonist, With Isoproterenol, Terbutaline, and CL-316243

OBJECTIVES To compare the potency and ureteral selectivity of the selective β(2)/β(3)-adrenoceptor agonist KUL-7211 with those of the nonselective β-adrenoceptor agonist isoproterenol, selective β(2)-adrenoceptor agonist terbutaline, and selective β(3)-adrenoceptor agonist CL-316243, we performed the study using an isolated porcine ureter and a porcine model of acute unilateral ureteral obstruction. METHODS The effects of the drugs on the 80-mM KCl-induced contraction of the ureteral segments isolated from male pigs were evaluated using a functional experimental technique. Anesthetized male miniature pigs with complete obstruction of the left lower ureter were used to evaluate the effects of the cumulative intravenous drug administration on the elevated intraureteral pressure and mean blood pressure. RESULTS The KCl-induced contractions in the isolated ureter were concentration-dependently attenuated by KUL-7211, isoproterenol, terbutaline, and CL-316243, with a rank order of potency of 6.26, 6.98, 5.41, and 5.41, respectively. In the anesthetized pigs, all 4 drugs reduced the unilateral ureteral obstruction-induced elevated intraureteral pressure in a dose-dependent manner, with KUL-7211 reducing it with a lower hypotensive effect than either isoproterenol or terbutaline. The ureteral selectivity (defined as the ratio of the effective dose to decrease the mean blood pressure by 25% to the effective dose to decrease the intraureteral pressure by 50%) of KUL-7211 (1.5) was significantly greater than that of isoproterenol (0.04) or terbutaline (0.43). CONCLUSIONS The present results have demonstrated that in pigs, KUL-7211 is a potent ureteral relaxant with a relatively small hypotensive effect. A selective β(2)/β(3)-adrenoceptor agonist, such as KUL-7211, warrants additional investigation as a potentially useful drug for the promotion of stone passage in patients with urolithiasis.

Silodosin, an α1A-Adrenoceptor Antagonist, May Ameliorate Ischemia-Induced Bladder Denervation and Detrusor Dysfunction by Improving Bladder Blood Flow

Background/Aims: This study was performed to investigate the detailed mechanism underlying the effects of the selective α1A-adrenoceptor antagonist, silodosin, on bladder function in a rat model of atherosclerosis-induced chronic bladder ischemia (CBI). Methods: The CBI model was prepared by balloon endothelial injury of the bilateral iliac arteries in male rats. Using an osmotic pump, the CBI rats received either silodosin or vehicle alone subcutaneously for 8 weeks. Rats received a 2% cholesterol diet throughout the experiment. Bladder blood flow (BBF) was measured. Immunohistochemical staining was performed to determine the nerve distribution and nerve growth factor expression in the bladder. Bladders were used for muscle strip contraction analysis. The expression levels of muscarinic M2 and M3 receptors were measured. Results: Silodosin abrogated the decrease in BBF in CBI rats. Silodosin prevented the decrease in nerve distribution and increase in nerve growth factor expression in the CBI model. Bladder contractile response was reduced in the CBI group. Silodosin ameliorated the effect on the bladder contractile response. The level of muscarinic M3 receptor mRNA present in the bladder of CBI rats was increased by silodosin. Conclusion: The results of this study suggest that silodosin ameliorates the denervation of the bladder and effects on detrusor contractile function under ischemic conditions by restoring BBF.