Function and expression differences between ergot and non-ergot dopamine D2 agonists on heart valve interstitial cells.

BACKGROUND AND AIM OF THE STUDY: The symptoms of Parkinson's disease are alleviated by dopamine D2 agonists, which are classified as ergot dopamine D2 agonists and non-ergot D2 agonists. Among the former, pergolide has been associated with valvular heart disease, since it has both potent D2 receptor and serotonin 5-HT(2B) receptor agonistic properties. Among the latter, pramipexole has few incidences of heart valve disease onset, since it has an absence of 5-HT(2B) receptor agonism. METHOD: A [3H]thymidine incorporation assay was performed to monitor function, and microarray global analysis to monitor gene expression, on porcine heart valve interstitial cells (VICs) treated with pergolide or pramipexole. RESULTS: The 5-HT(2B) receptor was abundantly expressed in porcine VICs. The 5-HT(2B) receptor agonist pergolide induced an increase in [3H]thymidine incorporation, accompanied by a decrease in 5-HT(2B) receptor mRNA expression. [3H]thymidine incorporation was blocked by lisuride, a 5-HT(2B) receptor antagonist, and also by LY-294002, a specific inhibitor of PI3K and Akt. Moreover, type 2 iodothyronine deiodinase (Dio2) expression in porcine VICs treated with pergolide was shown, by a global analysis of mRNA, to be markedly increased compared to that induced by pramipexole. Such changes in VICs may correlate with the mechanism of heart valve disease pathogenesis. CONCLUSION: There were substantial differences (increased [3H]thymidine incorporation, and Dio2 expression) between pergolide and pramipexole, which might correlate with the mechanism of heart valve disease onset.

Comparison of the effects of four α1-adrenoceptor antagonists on ejaculatory function in rats.

OBJECTIVE: To compare the effects of four α(1)-adrenoceptor (AR) subtype-selective antagonists on ejaculatory function in rats to investigate whether the differences in their modes of action-based on their selectivities for the α(1A)-AR subtype-would be related to the prevalence of ejaculation disorder (EjD). METHODS: The effects of α(1)-AR antagonists on noradrenaline-induced contractions were studied in rat isolated seminal vesicles, vas deferens, bladder trigone, and prostate. Male rats were given α(1)-AR antagonists orally and, 1 hour after the drug administration they were cohoused in pairs for 1 hour with untreated female rats certified to be in estrus. The number of copulatory plugs (NP) present after mating was measured as a marker of EjD. Drug effects on ejaculatory function (ie, on NP) were compared with those on the prostatic urethra (ie, phenylephrine-induced increase in intraurethral pressure [IUP]). RESULTS: All α(1)-AR antagonists concentration-dependently inhibited noradrenaline-induced contraction in all 4 tissues, and there were no differences in the rank order of potencies (tamsulosin > silodosin > alfuzosin > naftopidil) among the tissues. All α(1)-AR antagonists dose-dependently decreased NP and inhibited the phenylephrine-induced increase in IUP. There was little difference in the dose ratio ID(50) value (dose required to produce 50% inhibition) for NP/ID(50) value for IUP response among the four drugs. Drug potencies associated NP and IUP correlated closely with affinities for the human α(1A)-AR. CONCLUSION: α(1)-AR antagonists cause EjD as a class effect that depends on affinity for α(1A)-AR. Differences in α(1A)-AR selectivity would be unlikely to be related to the incidence of EjD.

Bladder selectivity of the novel ß3-agonist ritobegron (KUC-7483) explored by in vitro and in vivo studies in the rat.

We performed in vitro and in vivo experiments to evaluate the pharmacological profile of ritobegron and its effects on the bladder in rats. ß(3)-AR selectivity was assessed using CHO cells expressing various subtypes of the human ß-adrenoceptor (AR). Effects on isolated organs were evaluated using the organ-bath method. Effects on intravesical pressure, heart rate, and mean blood pressure were evaluated in urethane-anesthetized rats. Ritobegron increased cAMP accumulation in a concentration-dependent manner in CHO cells expressing any one of three human ß-AR, its selectivity for ß(3)-AR being 301-fold and 32-fold higher versus ß(1)-AR and ß(2)-AR, respectively. Ritobegron decreased the resting tension of the isolated bladder in a concentration-dependent manner (EC(50), 7.7 × 10(-8) mol/L; maximal relaxation, 97.0 %), and the ß(3)-AR antagonist SR58894A produced a parallel rightward-shift of this concentration-response curve without altering the maximal response [pK(B) value, 6.43]. Ritobegron concentration-dependently increased atrial rate and decreased myometrial contractions in vitro, and its selectivity for the bladder was 2,078-fold higher versus the atria and 14-fold higher versus the uterus. In vivo, ritobegron induced a dose-dependent decrease in intravesical pressure (ED(50) 0.4 mg/kg), without affecting heart rate and only slightly lowering mean blood pressure. Thus, ritobegron displayed potent and selective ß(3)-AR agonistic activity toward transfected human ß-AR and exhibited a high selectivity for the bladder versus other organs in rats. Moreover, it decreased intravesical pressure with minimal effects on the cardiovascular system in anesthetized rats. These results suggest that ritobegron shows promise as a potential agent for the treatment of overactive bladder.

Effects of ritobegron (KUC-7483), a novel selective ß3-adrenoceptor agonist, on bladder function in cynomolgus monkey.

We evaluated the pharmacological profile of ritobegron [KUC-7483; (-)-ethyl 2-[4-(2-{[(1S,2R)-2-hydroxy-2-(4-hydroxyphenyl)-1-methylethyl]amino}ethyl)-2,5-dimethylphenyloxy]acetate monohydrochloride] and its effects on the bladder in cynomolgus monkeys by in vitro and in vivo experiments. In vitro, ritobegron decreased the resting tension of the isolated bladder in a concentration-dependent manner (EC(50) 8.2 ± 2.3 × 10(-7) M; maximal relaxation 88.7 ± 3.7%). The ß(3)-adrenoceptor (AR) antagonist 3-(2-allylphenoxy)-1-[(1S)-1,2,3,4-tetrahydronaphth-1-ylamino]-(2S)-2-propanol hydrochloride (SR58894A) produced a rightward shift of this concentration-response curve without altering the maximal response (pK(B) value 6.56 ± 0.35). In isolated atria, ritobegron increased the atrial rate only at high concentrations (EC(50) 6.5 ± 1.2 × 10(-5) M). Ritobegron had no effect on tracheal contraction at concentrations from 10(-9) to 10(-4) M, and even at the highest concentration tested, 10(-3) M, the maximal relaxation it induced was only 26.7 ± 8.1%. Tests of the selectivity of ritobegron for the bladder gave values of 79.3- and 1200-fold higher versus atria and trachea, respectively. In the in vivo study ritobegron significantly decreased intravesical pressure (ED(50) 1.44 mg/kg) without affecting either mean blood pressure or heart rate. In conclusion, ritobegron displayed potent and selective ß(3)-AR agonistic activity and relaxed the monkey isolated bladder, and in vivo it decreased intravesical pressure without affecting cardiovascular parameters. These results suggest that ritobegron may be a promising potential agent for the treatment of overactive bladder.

Effects of ritobegron (KUC-7483), a novel ß3-adrenoceptor agonist, on both rat bladder function following partial bladder outlet obstruction and on rat salivary secretion: a comparison with the effects of tolterodine.

The objective of this study was to investigate the effects of the ß3-adrenoceptor (AR) agonist ritobegron on rat bladder function following partial bladder outlet obstruction and on rat salivary secretion. In addition, the effects of ritobegron were compared with those of the anti-muscarinic agent tolterodine. After a 6-week partial bladder outlet obstruction (BOO), drug effects on bladder functions were evaluated using cystometrography. Effects on carbachol (CCh)-induced salivary secretion were evaluated in urethane-anesthetized rats. Ritobegron significantly decreased the frequency of non-voiding contractions (NVC), while both ritobegron and tolterodine each significantly decreased the amplitude of NVC. Ritobegron had no effect on either the micturition pressure (MP) or the residual volume (RV). In contrast, tolterodine dose-dependently decreased MP and increased RV. Ritobegron had no effect on CCh-induced salivary secretion, whereas tolterodine dose-dependently decreased it. Ritobegron decreased both the frequency and amplitude of NVC, which is similar to its effect on the contractions associated with detrusor overactivity (DO) in patients with an overactive bladder (OAB), without affecting MP, RV, or CCh-induced salivary secretion. Although tolterodine reduced the amplitude of NVC, it also markedly increased RV and significantly inhibited CCh-induced salivary secretion. These results suggest that use of ritobegron, a ß3-AR agonist, is unlikely to lead to the residual urine and dry mouth symptoms that are associated with anti-muscarinic drugs, and that ritobegron may hold promise as a safe and effective agent for OAB treatment.

Effects of silodosin and naftopidil on the distal ureter and cardiovascular system in anesthetized dogs: comparison of potential medications for distal ureteral stone passage.

PURPOSE: We compared the effects of the selective alpha(1A)-adrenoceptor antagonist silodosin and the selective alpha(1D)-adrenoceptor antagonist naftopidil on intraureteral pressure in anesthetized dogs and evaluated their uroselectivity. MATERIALS AND METHODS: Using anesthesia the effects of silodosin and naftopidil were evaluated by the phenylephrine induced increase in intravesical ureteral pressure and on blood pressure. Each drug was administered intravenously in progressively increasing doses. The dose of each alpha(1)-adrenoceptor antagonist at which mean blood pressure was decreased by 15% (ED(15)) and the dose at which the phenylephrine induced increase in intravesical ureteral pressure was suppressed by 50% (ID(50)) were measured and uroselectivity was calculated as ED(15)/ID(50). RESULTS: Silodosin dose dependently suppressed the phenylephrine induced increase in intravesical ureteral pressure (ID(50) 2.5 microg/kg) but decreased mean blood pressure only at higher doses (ED(15) 143.4 microg/kg). In contrast, naftopidil decreased mean blood pressure (ED(15) 280.7 microg/kg) at the same doses as those that decreased the phenylephrine induced increase in intravesical ureteral pressure (ID(50) 225.1 microg/kg). Silodosin uroselectivity was markedly higher than that of naftopidil (58.6 vs 1.3). CONCLUSIONS: Results suggest that a selective alpha(1A)-adrenoceptor antagonist such as silodosin may facilitate distal ureteral stone passage at nonhypotensive doses.

Effects of four different alpha(1)-adrenoceptor antagonists on alpha-adrenoceptor agonist-induced contractions in isolated mouse and hamster ureters.

PURPOSE: To compare the efficacy of the selective alpha(1A)-adrenoceptor antagonist silodosin with those of doxazosin, terazosin, and alfuzosin against alpha-adrenoceptor agonist-induced contractions in mouse and hamster ureters. METHODS: The four alpha(1)-adrenoceptor antagonists were evaluated against norepinephrine-induced phasic contractions in mouse isolated ureteral preparations and against phenylephrine-induced sustained contractions in hamster isolated ureteral preparations using a functional experimental technique. RESULTS: In mouse ureters, silodosin (a selective alpha(1A)-adrenoceptor antagonist), doxazosin (a nonselective alpha(1)-adrenoceptor antagonist), terazosin (a nonselective alpha(1)-adrenoceptor antagonist), and alfuzosin (a nonselective alpha(1)-adrenoceptor antagonist) all shifted the norepinephrine concentration-response curve to the right. The rank order of potencies (pK(B) value) was silodosin (9.47 +/- 0.16) > doxazosin (8.62 +/- 0.15) > terazosin (8.39 +/- 0.16) > alfuzosin (8.03 +/- 0.12). In hamster ureters, all four antagonists shifted the phenylephrine concentration-response curve to the right, the rank order of potencies being silodosin (10.09 +/- 0.13) > doxazosin (8.22 +/- 0.16) > terazosin (7.75 +/- 0.15) > alfuzosin (7.70 +/- 0.10). In each case, silodosin was much more potent than the other three drugs. CONCLUSION: In this study, silodosin suppressed both mouse and hamster ureteral contractions more potently than doxazosin, terazosin, or alfuzosin. Hence, this alpha(1A)-adrenoceptor antagonist warrants further study as a potentially very useful medication for stone passage in urolithiasis patients.

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 veterinarian's 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.

Mechanical function and gene expression of alpha(1)-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.

Gene expressions and mechanical functions of α1-adrenoceptor subtypes in mouse ureter.

PURPOSE: This study was performed to characterize the α1-adrenoceptor subtypes in mouse ureters as regards gene expressions and contractile functions. METHODS: The mRNAs for these subtypes were quantified by the real-time quantitative reverse transcription polymerase chain reaction. In a functional study, α1-adrenoceptor antagonists were evaluated against the noradrenaline-induced contraction in mouse isolated ureteral preparations. RESULTS: In mouse ureter, the relative mRNA expression levels for α1a-, α1b- and α1d-adrenoceptors were 74.5, 14.3 and 11.2%, respectively. Adrenaline and noradrenaline each produced a concentration-dependent phasic contraction (pD 2 values, 5.73±0.05 and 5.69±0.06, respectively). Prazosin (non-selective α1-adrenoceptor antagonist), silodosin (selective α1A-adrenoceptor antagonist), and BMY-7378 (selective α1D-adrenoceptor antagonist) all shifted the concentration­response curve for noradrenaline to the right, the rank order of potencies (apparent pA 2 values) being silodosin (9.32±0.11)>prazosin (8.55±0.10)>BMY-7378 (6.06±0.15). The α1A-adrenoceptor antagonist silodosin was thus much more effective than the α1D-adrenoceptor antagonist BYM-7378. CONCLUSIONS: Our results demonstrate that in mouse ureters: the mRNA for the α1A-adrenoceptor was more prevalent than those for the α1B- and α1D-adrenoceptors, and that among these subtypes, the α1A-adrenoceptor plays the major role in noradrenaline-induced contraction.

Orally active factor Xa inhibitors: investigation of a novel series of 3-amidinophenylsulfonamide derivatives using an amidoxime prodrug strategy.

A series of novel and potent 3-amidinophenylsulfonamide derivatives of factor Xa inhibitors were designed and synthesized using an amidoxime prodrug strategy. We focused on systemic clearance of parent compounds in rats, and performed in vivo pharmacokinetic screening. Incorporation of a carboxymethoxy group markedly improved systemic clearance (compound 43), and the related amidoxime 44 showed sufficient prodrug conversion. Compound 45, the double prodrug of 43, exhibited practicable bioavailability after oral administration in rats. Among the various compounds under investigation, KFA-1982 was selected for clinical development.