Function and distribution of autonomic receptors in canine ureteral smooth muscle

A Concise and Useful Guide to Understand How Alpha1 Adrenoceptor Antagonists Work

Adrenoceptors are the receptors for the catecholamines, adrenaline and noradrenaline. They are divided in α (α1 and α2) and β (β1, β2 and β3). α1-Adrenoceptors are subdivided in α1A, α1B and α1D. Most tissues express mixtures of α1-adrenoceptors subtypes, which appear to coexist in different densities and ratios, and in most cases their responses are probably due to the activation of more than one type. The three subtypes of α1-adrenoceptors are G-protein-coupled receptors (GPCR), specifically coupled to Gq/11. Additionally, the activation of these receptors may activate other signaling pathways or different components of these pathways, which leads to a great variety of possible cellular effects. The first clinically used α1 antagonist was Prazosin, for Systemic Arterial Hypertension (SAH). It was followed by its congeners, Terazosin and Doxazosin. Nowadays, there are many classes of α-adrenergic antagonists with different selectivity profiles. In addition to SAH, the α1-adrenoceptors are used for the treatment of Benign Prostatic Hyperplasia (BPH) and urolithiasis. This antagonism may be part of the mechanism of action of tricyclic antidepressants. Moreover, the activation of these receptors may lead to adverse effects such as orthostatic hypotension, similar to what happens with the antidepressants and with some antipsychotic. Structure-activity relationships can explain, in part, how antagonists work and how selective they can be for each one of the subtypes. However, it is necessary to develop new molecules which antagonize the α1-adrenoceptors or make chemical modifications in these molecules to improve the selectivity, pharmacokinetic profile and/or reduce the adverse effects of known drugs.

Role of α- and β-adrenergic signaling in phenotypic targeting: significance in benign and malignant urologic disease

The urinary tract is highly innervated by autonomic nerves which are essential in urinary tract development, the production of growth factors, and the control of homeostasis. These neural signals may become dysregulated in several genitourinary (GU) disease states, both benign and malignant. Accordingly, the autonomic nervous system is a therapeutic target for several genitourinary pathologies including cancer, voiding dysfunction, and obstructing nephrolithiasis. Adrenergic receptors (adrenoceptors) are G-Protein coupled-receptors that are distributed throughout the body. The major function of α1-adrenoceptors is signaling smooth muscle contractions through GPCR and intracellular calcium influx. Pharmacologic intervention of α-and β-adrenoceptors is routinely and successfully implemented in the treatment of benign urologic illnesses, through the use of α-adrenoceptor antagonists. Furthermore, cell-based evidence recently established the antitumor effect of α1-adrenoceptor antagonists in prostate, bladder and renal tumors by reducing neovascularity and impairing growth within the tumor microenvironment via regulation of the phenotypic epithelial-mesenchymal transition (EMT). There has been a significant focus on repurposing the routinely used, Food and Drug Administration-approved α1-adrenoceptor antagonists to inhibit GU tumor growth and angiogenesis in patients with advanced prostate, bladder, and renal cancer. In this review we discuss the current evidence on (a) the signaling events of the autonomic nervous system mediated by its cognate α- and β-adrenoceptors in regulating the phenotypic landscape (EMT) of genitourinary organs; and (b) the therapeutic significance of targeting this signaling pathway in benign and malignant urologic disease. Video abstract.

Is Medical Therapy for Distal Ureteral Stones Efficient? Tamsulosin versus Deflazacort: A Prospective Randomised Trial

INTRODUCTION

 To evaluate the efficacy of tamsulosin and deflazacort in the spontaneous expulsion of distal ureteral stones when applied in an independent or combined manner.

METHODS

 134 patients with distal ureteral stones (4 - 10 mm) were included in tothe study. All patients were randomized into four groups: group 1 (n = 37) patients receiving tamsulosin (0.4 mg/day); group 2 (n = 26) patients receiving deflazacort (30 mg/day); group 3 (n = 37) patients receiving combined treatment (tamsulosin and deflazacort) with the same dosages; and group 4, control group cases (n = 34), receiving paracetamol on demand. Although deflazacort treatment was limited to 10 days due to the possible associated side effects, α-blocker and paracetamol lasted up to four weeks. Patients were followed up on a weekly basis and at the end of four weeks all groups were compared primarily with respect to the stone expulsion rates.

RESULTS

 No statistically significant difference was noted between all groups regarding the age, sex, or stone burden (p > 0.05). Spontaneous stone expulsion rates after 4 weeks were 64.8 %, 69.2 %, 75.7 %, and 26.4 % in group 1, 2, 3, and 4 respectively. Spontaneous passage rates were statistically higher in all treatment groups when compared with the control group. Despite the highest spontaneous stone expulsion rate noted in group 3; this difference was not statistically significant when compared with the group 1 and 2. No major side effect related to the medications was observed.

CONCLUSIONS

 Tamsulosin facilitated the spontaneous passage of distal ureteral stones < 10 mm in size in an effective manner particularly when applied in combination with an oral corticosteroid.

Medical expulsive therapy for ureter stone using naftopidil: A multicenter, randomized, double-blind, and placebo-controlled trial

Objectives

A prospective, multicenter, randomized, double-blind, placebo-controlled trial evaluated the effects of naftopidil 75 mg for medical expulsive therapy for a single ureter stone.

Materials and methods

Patients diagnosed with a ureter stone were prescribed aceclofenac 100 mg or a combined medication of tramadol 37.5 mg and acetaminophen 325 mg. Patients then randomly received either naftopidil 75 mg or placebo. Primary endpoint was the stone passage rate at 14 days after medication.

Results

The 150 patients enrolled in 6 institutions randomly received either naftopidil (n = 75) or placebo (n = 75). The percentages of ureter stone passed spontaneously 14 days after medication was 60.9% in the naftopidil group and 53.3% in the placebo group. Stone-free rates and the total use of analgesics showed no significant differences between the two groups. Stone-free rates at 14 days after medication were decreased when maximal stone size was increased: 39.4% (≥ 5 mm), 15.5% (≥ 6 mm), and 7.0% (≥ 7 mm).

Conclusions

The use of naftopidil 75 mg once daily was not effective in increasing spontaneous stone passage rates or reducing analgesic use. The maximal stone size < 6 mm and the follow-up for two weeks would be appropriate for applying medical expulsive therapy to patients with a single ureter stone.

Precise Characterization and 3-Dimensional Reconstruction of the Autonomic Nerve Distribution of the Human Ureter

PURPOSE

We sought to characterize and 3-dimensionally reconstruct the distribution of the autonomic innervation of the human ureter.

MATERIALS AND METHODS

Three male and 3 female pairs of ureters were evaluated at 2 mm serial transverse sections along the entire length of the ureter. The location of nerve tissue was immunohistochemically identified using the neuronal marker, S100 protein. ImageJ software was used to calculate nerve count and density in the adventitia and smooth muscle. Blender® graphics software was used to create a 3-dimensional reconstruction of autonomic nerve distribution.

RESULTS

Within the adventitia nerve density was highest in the mid and distal ureter (females 2.87 and 2.71 nerves per mm², and males 1.68 and 1.69 nerves per mm²) relative to the proximal ureter (females and males 1.94 and 1.22 nerves per mm², respectively, p >0.0005). Females had significantly higher nerve density throughout the adventitia, especially in the distal ureter (2.87 vs 1.68 nerves per mm², p <0.0005). In smooth muscle the nerve density progressively increased from the proximal to the distal ureter (p >0.0005). Smooth muscle nerve density was similar in the 2 genders (p = 0.928). However, in females nerve density was significantly higher in the first 2 cm of the distal ureter relative to the second 2 cm (3.6 vs 1.5 nerves per mm², p <0.001) but not in males (3.0 vs 2.1 nerves per mm², p = 0.126).

CONCLUSIONS

Nerve density was highly concentrated at the distal ureter in the adventitia and smooth muscle of the male and female human ureters. The female ureter had greater nerve density in the adventitia, and in smooth muscle nerves were significantly concentrated at the ureteral orifice and the ureteral tunnel.

Effects by silodosin on the partially obstructed rat ureter in vivo and on human and rat isolated ureters

BACKGROUND AND PURPOSE

α1 -adrenoceptor (-AR) antagonists may facilitate ureter stone passage in humans. We aimed to study effects by the α1 A -AR selective antagonist silodosin (compared to tamsulosin and prazosin) on ureter pressures in a rat model of ureter obstruction, and on contractions of human and rat isolated ureters.

EXPERIMENTAL APPROACH

After ethical approval, ureters of male rats were cannulated beneath the kidney pelvis for in vivo ureteral intraluminal recording of autonomous peristaltic pressure waves. A partial ureter obstruction was applied to the distal ureter. Mean arterial blood pressure (MAP) was recorded. Approximate clinical and triple clinical doses of the α1 -AR antagonists were given intravenously. Effects by the α1 -AR antagonists on isolated human and rat ureters were studied in organ baths.

KEY RESULTS

Intravenous silodosin (0.1-0.3 mg kg(-1) ) or prazosin (0.03-0.1 mg kg(-1) ) reduced obstruction-induced increases in intraluminal ureter pressures by 21-37% or 18-40% respectively. Corresponding effects by tamsulosin (0.01 or 0.03 mg kg(-1) ) were 9-20%. Silodosin, prazosin and tamsulosin reduced MAP by 10-12%, 25-26% (P < 0.05), or 18-25% (P < 0.05) respectively. When effects by the α1 A -AR antagonists on obstruction-induced ureter pressures were expressed as a function of MAP, silodosin had six- to eightfold and 2.5- to eightfold better efficacy than tamsulosin or prazosin respectively. Silodosin effectively reduced contractions of both human and rat isolated ureters.

CONCLUSIONS AND IMPLICATIONS

Silodosin inhibits contractions of the rat and human isolated ureters and has excellent functional selectivity in vivo to relieve pressure-load of the rat obstructed ureter. Silodosin as pharmacological ureter stone expulsive therapy should be clinically further explored.

Effect of Flos carthami Extract and α 1-Adrenergic Antagonists on the Porcine Proximal Ureteral Peristalsis

Traditional Chinese medicine (TCM) has been proposed to prevent urolithiasis. In China, Flos carthami (FC, also known as Carthamus tinctorius) (Safflower; Chinese name: Hong Hua/紅花) has been used to treat urological diseases for centuries. We previously performed a screening and confirmed the in vivo antilithic effect of FC extract. Here, ex vivo organ bath experiment was further performed to study the effect of FC extract on the inhibition of phenylepinephrine (PE) (10⁻⁴ and 10⁻³ M) ureteral peristalsis of porcine ureters with several α₁-adrenergic antagonists (doxazosin, tamsulosin, and terazosin) as experimental controls. The results showed that doxazosin, tamsulosin, and terazosin dose (approximately 4.5 × 10⁻⁶ − 4.5 × 10⁻¹  μg/mL) dependently inhibited both 10⁻⁴ and 10⁻³ M PE-induced ureteral peristalsis. FC extract achieved 6.2% ± 10.1%, 21.8% ± 6.8%, and 24.0% ± 5.6% inhibitions of 10⁻⁴ M PE-induced peristalsis at doses of 5 × 10³, 1 × 10⁴, and 2 × 10⁴  μg/mL, respectively, since FC extract was unable to completely inhibit PE-induced ureteral peristalsis, suggesting the antilithic effect of FC extract is related to mechanisms other than modulation of ureteral peristalsis.

Early hospital admission and treatment onset may positively affect spontaneous passage of ureteral stones in patients with renal colic

OBJECTIVE

To evaluate the impact of early hospital admission and onset of medical expulsive therapy (MET) in spontaneous passage of ureteral stones causing renal colic.

METHODS

We recruited 392 patients referred to the emergency room with symptoms of renal colic. All patients received standard MET of oral tamsulosin 0.4 mg at the time of diagnosis. In group A, patients who received MET in <2 hours from the symptom onset were included, whereas group B consisted of patients treated in >2 hours. The association of MET onset and stone-free rates after 6 weeks of follow-up was evaluated. Early MET onset predictive impact on spontaneous stone passage was evaluated as well.

RESULTS

The stone-free rate in group A and B patients was 71.2% and 59.7% (P=.018), respectively. A significant association was observed between spontaneous calculus elimination and stone size (P≤.001), location within the ureter (P=.007), and the interval between pain onset and pharmaceutical management (P=.018). Patients who received a late-onset MET had an increased risk to develop febrile upper urinary tract infection during the follow-up period (P=.040). In the multivariate analysis, size (P≤.001) and early therapy onset (P=.019) were statistically important predictors for stone-free status after the surveillance period.

CONCLUSION

Patients with renal colic who admitted to the emergency department earlier since symptom onset may have increased potential to be stone free during the surveillance period.

Effect of tamsulosin on stone expulsion in proximal ureteral calculi: an open-label randomized controlled trial

AIM

Medical expulsive therapy (MET) using alpha-blockers is effective for distal ureteral calculi (UC). We aimed to evaluate the efficacy of tamsulosin for proximal UC expulsion.

MATERIALS AND METHODS

An open-label randomized controlled trial was conducted with 108 patients who agreed to conservative management for single, radiopaque, proximal UC ≤ 6 mm and were randomized into group A (n = 54, conservative managements only) or B (n = 54, 0.2 mg tamsulosin once a day). The primary end-point was stone passage rates (SPR) in the intention-to-treat population in 4 treatment weeks. The secondary end-points were estimated in per-protocol population and were time to stone passage, post-trial Euro-quality-of-life (EuroQOL) score, oral analgesic requirements, and willingness to undergo conservative treatment again.

RESULTS

The two groups were well balanced in terms of baseline patient and stone characteristics. Seventy nine patients (73.2%; 35 of group A and 44 of group B) completed the study protocol. The overall SPR was 60.2% (65/108). Group B had a higher SPR (74.1%; 40/54) than group A (46.3%; 25/54; p = 0.003) and a significantly shorter time to stone passage (mean days, A: 19.6 vs. B: 14.3, p = 0.005). The groups did not differ in post-trial EuroQOL score or oral analgesic requirements, whereas 74.3% (26/35) of group A and 90.9% (40/44) of group B were willing to undergo conservative treatment again (p = 0.048). Univariate logistic regression analysis showed that stone size (OR = 1.447, p = 0.045) and tamsulosin treatment (OR = 3.314, p = 0.004) significantly predicted stone expulsion. On multivariate analysis, only tamsulosin was statistically significant (OR=3.198, p = 0.021).

CONCLUSIONS

Tamsulosin was associated with significantly higher stone expulsion rate and shorter expulsion time in proximal UC ≤ 6 mm compared with conservative managements only. Our results indicate that similar to patients with distal UC, MET using tamsulosin is a reasonable treatment option for patients with proximal UC.

Impact of tamsulosin on ureter stone expulsion in korean patients: a meta-analysis of randomized controlled studies

Purpose

Using meta-analysis, the study's aim was to evaluate the efficacy of tamsulosin, an alpha-blocker, in the treatment of ureteral stones with or without shockwave lithotripsy (SWL) in Korean patients.

Materials and Methods

Relevant randomized controlled studies published through June 2011 were identified in a search of MEDLINE, KoreaMed, and the Korean Medical Database. No language restriction was applied. Only randomized controlled trials conducted with Korean patients were eligible for the analysis. The primary outcome assessed was the stone clearance rate. Two reviewers independently assessed the quality of the study and extracted the data. Meta-analysis was conducted by using R, version 2.13.0.

Results

A total of 6 articles were selected as being suitable for evaluation. Pooling of the trials demonstrated a 43% higher expulsion rate for tamsulosin treatment compared to a control group (risk ratio [RR], 1.43; 95% confidence interval [CI]: 1.24 to 1.65). Similar results were obtained in all subgroup analyses according to stone location (upper: RR, 1.31; 95% CI, 1.02 to 1.68, lower: RR, 1.50; 95% CI, 1.20 to 1.88) or concomitant SWL (yes: RR, 1.38; 95% CI, 1.14 to 1.68, no: RR, 1.48; 95% CI, 1.21 to 1.83).

Conclusions

This meta-analysis of randomized controlled studies provides a high level of evidence supporting the suggestion that treatment with tamsulosin augments the stone expulsion rate for ureter stones with or without SWL in a Korean population. However, a high-quality, large-scale, multicenter, randomized controlled trial is warranted to fully support this hypothesis.

β-Adrenergic Receptor Subtypes in the Urinary Tract

Within the urinary tract, β-adrenergic receptors (AR) are found largely on smooth muscle cells but are also present, at least in the bladder, in the urothelium and on afferent nerves. Our understanding of β-AR subtype expression and function is hampered by a lack of well-validated tools, particularly with regard to β(3)-AR. Moreover, the β-AR subtypes involved in a specific function may differ between species. In the ureter, β-AR can modulate pacemaker activity and smooth muscle tone involving multiple subtypes. In the human bladder, β-AR promote urine storage. Bladder smooth muscle relaxation primarily involves β(3)-AR, and the agonists selective for this subtype are in clinical development to treat bladder dysfunction. While prostate and urethra also express β-AR, the overall physiological role in these tissues remains unclear.

α(1)-Adrenoceptors in the urinary tract

α(1)-Adrenoceptors have been identified and characterized extensively by functional, radioligand-binding, and molecular biological techniques. Molecular clones have been isolated for three α(1)-subtypes (α(1a), α(1b), and α(1d)), and these subtypes are also functionally characterized. α(1)-Adrenoceptors are present in the prostate, urethra, bladder (urothelium, smooth muscle, and afferent nerves), ureter, vas deferens, peripheral ganglia, nerve terminals, vascular tissues, and central nervous system (CNS), and they could all potentially influence overall urinary function and contribute to both the therapeutic and adverse effects of α(1)-adrenoceptor antagonists in patients with benign prostatic hyperplasia (BPH) and lower urinary tract symptoms (LUTS). This review aimed to discuss the relevant physiological and pharmacological roles and molecular biology of α(1)-adrenoceptor subtypes in the prostate, urethra, bladder, ureter, and CNS.

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.

Demonstration of intrinsic innervation of the guinea pig upper urinary tract using whole-mount preparation

AIMS

The morphology and functional importance of the autonomic nervous system in the upper urinary tract is still not completely understood. Previous histological studies investigating the innervation of the urinary tract have mainly used conventional sections in which the three-dimensional structure of the intramural innervation is difficult to achieve. In contrast, the whole-mount preparation technique is a suitable method for visualizing the distribution of the mesh-like neuronal networks within the urinary tract.

METHODS

The distribution and regional variation of neurofilament (NF), tyrosine hydroxylase (TH), choline acetyltransferase (ChAT), and substance P-immunoreactive (SP-IR) neurons, as well as acetylcholinesterase (AChE) and nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d)-positive neurons were investigated using whole-mount preparations of the guinea pig upper urinary tract.

RESULTS

Two distinct nervous plexuses were detected within the muscle layers containing NF, TH, ChAT, and SP-IR nerves. AChE-positive nerves were seen in all layers. Only moderate NADPH-d-positive innervation was found. Renal pelvis, upper and lower part of the ureter showed an overall increased innervation compared to the middle portion of the ureter. Ganglia were found at the pelviureteric border displaying NF and TH immunoreactivity.

CONCLUSION

The whole-mount preparation technique provides an elegant method for assessing the three-dimensional architecture of ureteral innervation. The guinea pig upper urinary tract is richly supplied with adrenergic, cholinergic, nitrergic, and sensory nerves which suggest that the autonomous nervous system plays an important role in controlling ureteral motility and blood flow.

Physiology and pharmacology of the human ureter: basis for current and future treatments

INTRODUCTION

This article sets out to be a review regarding agents that affect contraction and relaxation of the ureter in order to establish a basis for current and future treatments for upper urinary tract obstruction.

MATERIAL AND METHODS

A complete review of the English literature using MEDLINE was performed between 1960 and 2007 on ureter physiology and pharmacology with special emphasis on signal transduction mechanisms involved in the contractile regulation of the human ureter.

RESULTS

Activation of muscarinic and adrenergic receptors increases the amplitude of ureteral contractions. The sympathetic nerves modulate the contractions by alpha-adrenoceptors and relaxation by beta-adrenoceptors. The purinergic system is important in sensory/motor functions and ATP is an important non-adrenergic non-cholinergic (NANC) agent causing contraction. Nitric oxide (NO) is a major inhibitory NANC neurotransmitter causing relaxation. Serotonin causes contraction. Prostaglandin-F(2)alpha contracts whereas prostaglandin-E(1)/E(2) relaxes the ureter. Phosphodiesterases (PDE) and the Rho-kinase pathway have recently been identified in the human ureter. PDE-IV inhibitors, K(+) channel openers, calcium antagonists, alpha(1)-adrenoceptor antagonists and NO donors seem to be promising drugs in relieving obstruction and facilitating stone passage.

CONCLUSIONS

Further understanding of the ureteral function and pharmacology may lead to the discovery of promising new drugs that could be useful in relieving ureteral colic, facilitating spontaneous stone passage, preparing the ureter for ureteroscopy as well as acting adjunctive to extracorporeal shock-wave lithotripsy.

Doxazosin for the Management of Distal-Ureteral Stones

PURPOSE

To evaluate the efficacy of doxazosin in inducing spontaneous passage of stones in the distal ureter and to compare its efficacy according to the size of the stone.

PATIENTS AND METHODS

Seventy-three patients with a mean age of 46.38 +/- 10.17 years who presented with a distal-ureteral stone were divided into four groups according to stone size and drug treatment: <5 mm without doxazosin (group A; n=15); 5-10 mm (group B; n=16); <5 mm with doxazosin 4 mg/day for 4 weeks (group C; n=20); and 5-10 mm with doxazosin 4 mg/day for 4 weeks (group D; n=22). Groups A and B served as controls for groups C and D, respectively.

RESULTS

Spontaneous stone passage was documented in 9 patients (60%) in group A v 17 (85%) in group C (P=0.047) and 7 (43.75%) in group B v 16 (72.73%) in group D (P=0.036). The average expulsion time was 8.78 +/- 1.09 days in group A v 7.59 +/- 0.80 days in group C (P=0.004) and 12.14 +/- 1.35 days in group B v 7.06 +/- 1.29 days in group D (P<0.0001). The number of pain episodes in group D patients was significantly lower than in group B (P +/- 0.0078).

CONCLUSIONS

Doxazosin treatment proved to be safe and effective for distal-ureteral stones, as determined by earlier expulsion, decreased colic frequency, and absence of side effects. The efficacy of doxazosin was significantly higher for 5-to 10-mm stones than for smaller ones.

Alpha1 Adrenoceptors in Human Urinary Tract: Expression, Distribution and Clinical Implications

Adrenergic receptors (ARs) are a class of proteins belonging to the G protein-coupled receptor family. Pharmacological and molecular studies allowed dividing ARs into three different categories: α1, α2 and β. In this review, we focused on α1 ARs and α1 AR antagonists, since α 1 ARs play an important role in the pathophysiology of a number of urinary tract (UT) dysfunctions. α1 ARs are widely expressed in human UT; in particular, the three ureter areas (distal, medial and proximal) show different patterns of receptor expression (i.e. distal > medial = proximal), giving the molecular basis for the use of α1 ARs antagonist in the expulsive therapy of distal ureter calculi. Bladder areas are characterized by important differences among trigone, detrusor and neck, the first showing a different pattern of expression compared to the other parts. Further, there are evidences of both density and subtype gender-dependent expressions. α1 ARs expression in prostate and detrusor is a widely investigated area of research, mainly due to the clinical impact of benign prostatic hyperplasia (BPH). Urethra has not been well studied in human, although it plays a role in the control of continence.

Studies carried out on α1 AR subtype expression in the UT indicate that, although the presence of each subtype is observed, α1A firstly and then α1D ARs seem to be more expressed than α1B ARs. Thus, drugs that demonstrate high α1A/D AR selectivity have drawn the researchers’ attention. As it relates specifically to the α1 AR antagonists used in the treatment of lower UT symptoms, the concept of uroselectivity has been operationally defined; indeed, in a number of recent publications uroselectivity has been defined as the degree to which a given compound inhibits norepinephrine-induced increase in urinary muscle contractions and/or its propensity to generate unwanted cardiovascular effects, such as decreases in blood pressure.

Current opinion in urology: new insights into nephrolithiasis

PURPOSE OF REVIEW

Recent studies in nephrolithiasis have investigated why stones form, improvements in medical therapy, and advances in surgical therapy. We outline recent research in these areas.

RECENT FINDINGS

We describe a series of articles characterizing the histopathology of Randall's plaques and the renal papillae in patients with nephrolithiasis, detailing genetic discoveries related to uric acid stones, describing further uses of alpha-antagonists in nephrolithiasis, and reporting improvements in extracorporeal shockwave lithotripsy technique and outcomes.

SUMMARY

Characterization of the renal papillae and Randall's plaques in different types of stones may guide the urologist in treating stones and may lead to further research into how and where stones of different compositions form.

Effect of tamsulosin on the number and intensity of ureteral colic in patients with lower ureteral calculus

BACKGROUND

We aimed to objectively determine whether tamsulosin as an alpha(1)-blocker was effective in patients who had ureterolithiasis located in the lower part of the ureter.

METHODS

Sixty patients with lower ureteral calculi (juxtavesical or intramural portion) were included in the present study. Conservative treatment, such as hydration and tenoxicam as a non-steroidal anti-inflammatory drug, was given to group 1 (30 patients). Group 2 (30 patients) was given tamsulosin (0.4 mg daily) in addition to the conservative treatment. All patients were followed up and questioned about the numbers and intensity of ureteral colic, and the rates of spontaneous passage after the procedure.

RESULTS

Spontaneous passage was observed in 22 of the 30 patients in group 1 (73.3%) and 26 of the 30 patients in group 2 (86.6%). The difference within groups 1 and 2 was not significant (P=0.196). The difference between both groups was not statistically significant either, with the stone diameter being 6 mm (P=0.635) or >6 mm (P=0.407). As group 1 patients were passing their stones, they had more ureteral colic episodes than group 2 patients. This difference was statistically significant and correlated well with the administration of tamsulosin (P=0.038). Group 1 patients reported higher scores according to a visual analog scale than group 2 patients. Also, this difference was statistically significant (P=0.000).

CONCLUSIONS

We think that the treatment of alpha(1)-blockers decreased the number of ureteral colic episodes and the intensity of pain during spontaneous passage at the lower ureteral calculi. Also, it will be beneficial to patients' quality of life.

Role of tamsulosin in treatment of patients with steinstrasse developing after extracorporeal shock wave lithotripsy

OBJECTIVES

To evaluate whether tamsulosin, as an alpha(1)-blocker, was effective for the treatment of steinstrasse in the lower ureter after shock wave lithotripsy.

METHODS

A total of 67 patients (43 men and 24 women) with steinstrasse in the lower portion of the ureters were randomly divided into two groups. Only hydration and tenoxicam (20 mg orally once daily) was given to group 1 (35 patients). Group 2 (32 patients), was also given tamsulosin (0.4 mg daily). All patients were reevaluated and questioned about the number of episodes and severity of ureteral colic and the rates of spontaneous resolution of steinstrasse 6 weeks after beginning treatment. They were asked to score the severity of pain according to a visual analog scale.

RESULTS

In 23 (65.7%) of 35 patients in group 1 and in 24 (75%) of 32 patients in group 2, steinstrasse resolved during the first 6 weeks. The resolution rates were not significantly different (P >0.05) between groups 1 and 2. Group 1 had more ureteral colic episodes than did group 2 while passing their stones. This difference was statistically significant (P <0.01). Group 1 patients reported significantly greater (P <0.001) visual analog scale scores than did group 2 patients.

CONCLUSIONS

The addition of tamsulosin to conservative treatment seemed to be beneficial in terms of the reduced number of ureteral colic episodes and the severity of pain in the patients who developed steinstrasse after shock wave lithotripsy.

RANDOMIZED TRIAL OF THE EFFICACY OF TAMSULOSIN, NIFEDIPINE AND PHLOROGLUCINOL IN MEDICAL EXPULSIVE THERAPY FOR DISTAL URETERAL CALCULI

PURPOSE

Recent studies show the interesting efficacy of different drug combinations for the spontaneous expulsion of distal ureteral stones. We performed a randomized, prospective study to assess and compare the efficacy of 3 drugs as medical expulsive therapy for distal ureteral calculi.

MATERIALS AND METHODS

A total of 210 symptomatic patients with distal ureteral calculi greater than 4 mm were randomly allocated to home treatment with phloroglucinol, tamsulosin or nifedipine (groups 1 to 3, respectively). Each group was given a corticosteroid drug and antibiotic prophylaxis with an injectable nonsteroidal anti-inflammatory drug was also used on demand. The primary end point was the expulsion rate and the secondary end points were expulsion time, analgesic use, need for hospitalization and endoscopic treatment as well as the number of workdays lost, quality of life and drug side effects

RESULTS

The expulsion rate was significantly higher in group 2 (97.1%) than in groups 1 (64.3%, p <0.0001) or 3 (77.1%, p <0.0001). Group 2 significantly achieved stone passage in a shorter time than the other 2 groups and showed a significantly decreased number of hospitalizations as well as a better decrease in endoscopic procedures performed to remove the stone. The control of renal colic pain was significantly superior in group 2 compared with the other groups, resulting in fewer workdays lost. Group 3 showed lower analgesic use and decreased workdays lost compared with group 1. No difference in side effects was observed among the groups.

CONCLUSIONS

Medical expulsive therapy should be considered for distal ureterolithiasis without complications before ureteroscopy or extracorporeal lithotripsy. The use of tamsulosin in this treatment regimen produced stone expulsion in almost all cases in a short time, allowing complete home patient treatment.

Evidence for the presence of alpha1 adrenoceptor subtypes in the human ureter

AIM

Several studies have proposed a role for alpha1 adrenoceptors (ARs) in ureteral physiology, indicating that they are present in the ureter; however, few studies have been done to identify alpha1 AR subtypes present in this area. Thus, this study was carried out to characterize the alpha1 AR subtype gene and protein expression in proximal, medial, and distal region of the human ureter.

METHODS

Molecular characterization of alpha1 AR subtypes were analyzed by semi-quantitative RT-PCR. alpha1 AR protein expression was studied by saturation binding curves and by competition binding curves with selective antagonists. Analysis of data was performed using the GraphPad PRISM 4 software.

RESULTS

Analysis of saturation binding curves revealed a heterogeneous distribution of alpha1 AR binding sites, the B(max) for the distal ureter was indeed 52.5 +/- 5.4 fmol/mg prot, while a lower similar density of alpha1 ARs was demonstrated in the medial (25.2 +/- 1.7 fmol/mg prot) and proximal (23.4 +/- 0.4 fmol/mg prot) ureters. Molecular and pharmacological characterization of alpha1 AR subtypes indicated that each receptor was present, although with differences in terms of the amount expressed.

CONCLUSIONS

Human ureter was endowed with each alpha1 AR subtype, although alpha1D and alpha1A ARs were prevalent over alpha1B ARs. Radioligand binding results revealed that there were no significant differences in the K(d) between ureteral regions, while a heterogeneous distribution of alpha1 AR binding sites was detected, with the highest density of alpha1 ARs in the distal ureter and a lower similar density in the medial and proximal ureters.

Evidence for the Presence of α1 Adrenoceptor Subtypes in the Human Ureter

Several studies proposed a role for α1 adrenoceptors (α1 ARs) in the ureteral physiology, indicating that they are present in the ureter; however, few studies have been made to identify α1 AR subtypes present in this area. Thus, this study was carried out to characterize the α1 AR subtype gene and protein expression in proximal, medial and distal region of the human ureter.

Methods

Molecular characterization of α1 AR subtypes was done by semi-quantitative RT-PCR. The α1 AR protein expression was studied by saturation binding curves using the α1 AR antagonist 125I-HEAT. Analysis of data was performed using the GraphPad PRISM 4 software.

Results

Analysis of saturation binding curves revealed an heterogeneous distribution of α1 AR binding sites; the Bmax for the distal ureter was indeed 52.5 ±5.4 fmol/mg prot, while a lower similar density of α1 ARs was demonstrated in the medial (25.2 ±1.7 fmol/mg prot) and proximal (23.4 ±0.4 fmol/mg prot) ureters. Molecular characterization of α1 AR subtypes indicated that each receptor was present, although with differences in term of the amount expressed.

Conclusions

Human ureter was endowed with each α1 AR subtype, although α1D and α1A ARs were prevalent over α1B ARs. Radioligand binding results revealed that there were no significant differences in the Kd between ureteral regions, while an heterogeneous distribution of α1 AR binding sites was detected, with the highest density of α1 ARs in the distal ureter and a lower similar density in the medial and proximal ureter.

EFFECTS OF CHOLINERGIC DRUGS ON URETERAL FUNCTION IN ANESTHETIZED DOGS

PURPOSE

We evaluated the effects of the nonselective muscarinic receptor agonist carbachol (CCh) and its antagonist atropine on ureteral function in anesthetized dogs.

MATERIALS AND METHODS

Drug effects were evaluated on elevated pressure in a completely obstructed ureter and peristalsis in its partially obstructed fellow ureters as well as on intravesical isovolumetric pressure.

RESULTS

CCh (0.1 to 1.0 microg/kg intravenously) dose dependently decreased elevated pressure and peristalsis in completely and partially obstructed ureters, respectively, and increased intravesical isovolumetric pressure. On the other hand, atropine (0.1 to 1.0 mg/kg intravenously) had no significant effects on these 3 variables. Prior administration of atropine (1.0 mg/kg intravenously) completely inhibited the described CCh induced effects.

CONCLUSIONS

Our results demonstrate that in anesthetized dogs cholinergic receptor stimulation has a suppressive effect on ureteral pressure and peristalsis in obstructed ureters, in contrast to its activation of bladder smooth muscle.

Efficacy of Tamsulosin in the Medical Management of Juxtavesical Ureteral Stones

PURPOSE

We evaluated the efficacy of the alpha1-adrenergic antagonist tamsulosin for conservative expulsive therapy in patients with ureteral colic due to juxtavesical stones.

MATERIALS AND METHODS

A total of 60 consecutive symptomatic patients with stones located in the juxtavesical tract of the ureter were randomly divided into group 1--30 who received oral floroglucine-trimetossibenzene 3 times daily and group 2--30 who received 0.4 mg tamsulosin daily. The 2 groups received 30 mg deflazacort daily for 10 days plus cotrimoxazole 2 times daily for 8 days and 75 mg diclofenac injected intramuscularly on demand. Ultrasound followup and medical visits were performed weekly for 4 weeks. Stone passage rate and time, analgesic use, hospitalization and endoscopical intervention were evaluated. Statistical analysis was performed using the Student t test.

RESULTS

The stone expulsion rate was 70% for group 1 and 100% for group 2. Mean stone size was 5.8 and 6.7 mm, respectively (p = 0.001). Mean expulsion time was 111.1 hours for group 1 and 65.7 hours for group 2 (p = 0.020). The mean number of diclofenac injections was 2.83 for group 1 and 0.13 for group 2 (p <0.0001). Ten group 1 patients were hospitalized, of whom 9 underwent ureteroscopy, compared with none in group 2 (p <0.0001 and 0.001, respectively).

CONCLUSIONS

Tamsulosin used as a spasmolytic drug during renal colic due to juxtavesical calculi increased the stone expulsion rate and decreased expulsion time, the need for hospitalization and endoscopic procedures, and provided particularly good control of colic pain.

Pharmacological profile of KUL-7211, a selective beta-adrenoceptor agonist, in isolated ureteral smooth muscle

Since, in the human ureter, both beta(2)- and beta(3)-adrenoceptors mediate adrenergic-stimulation-induced relaxation, selective beta(2)-/beta(3)-adrenoceptor agonists might prove clinically useful for relieving ureteral colic and promoting stone passage. We evaluated the beta-adrenoceptor subtype selectivity and ureteral-relaxing efficacy of (-)-2-[4-(2-[[(1S,2R)-2-hydroxy-2-(4-hydroxyphenyl)-1-methylethyl]amin] ethyl)phenyloxy]acetic acid (KUL-7211), a new beta-adrenoceptor agonist, in vitro. In rat isolated organs, its selectivities, for inhibition of spontaneous uterine contraction (mediated via beta(2)-adrenergic stimulation) and inhibition of colonic contraction (via beta(3)-adrenergic stimulation) versus increase in atrial rate (via beta(1)-adrenergic stimulation), were 56.3 and 242.2, respectively. KUL-7211 relaxed 80-mM-KCl-induced tonic contractions in both rabbit (pD(2) value: 5.86 +/- 0.13, whose ureteral relaxation is mediated via beta(2)-adrenergic stimulation) and canine (pD(2) value: 6.52 +/- 0.16, via beta(3)-adrenergic stimulation) isolated ureters in a concentration-dependent manner. These KUL-7211-induced relaxing effects were antagonized by ICI-118,551 (selective beta(2)-adrenoceptor antagonist, pK(B) value: 8.91 +/- 0.24) in the rabbit ureter and by bupranolol (non-selective beta-adernoceptor antagonist, pK(B) value: 6.85 +/- 0.12) in the canine ureter. KUL-7211 also reduced the spontaneous rhythmic contraction in a canine ureteral spiral preparation in a concentration-dependent manner, the pD(2) value being 6.83 +/- 0.20. These data clearly demonstrate that KUL-7211 selectively stimulates both ureteral beta(2)- and beta(3)-adrenoceptors and potently relaxes ureteral smooth muscle. KUL-7211 may be a novel and useful medication for relieving ureteral colic and promoting stone passage in urolithiasis patients.

Modification of ureteral motility and promotion of urine flow around an intraureteral obstruction by CL-316243, phenylephrine, and furosemide in dogs

The aim of this study was to evaluate the effects of a beta3-adrenoceptor (AR) agonist (CL-316243), an alpha1-AR agonist (phenylephrine), and a loop diuretic (furosemide) on the spontaneous rhythmic contractions of the isolated canine ureter and on an acute ureteral obstruction produced by inflation of a balloon catheter in anesthetized dogs. In the isolated ureter, CL-316243 concentration dependently reduced both the amplitude and frequency of the rhythmic contractions (pD(2): 7.19 +/- 0.33), whereas phenylephrine significantly enhanced both variables (pD(2): 5.26 +/- 0.09) and furosemide reduced them only slightly. In the acute ureteral obstruction model, the intraureteral pressure (IUP) gradually rose to reach a plateau of 58.9 mm Hg after inflation of a balloon catheter within the lower ureter. Intravenous administration of CL-316243 (0.3 microg/kg) significantly reduced the elevated IUP and the resumed urine flow (UF), leading to a sustained reduction in the IUP. In contrast, the IUP continued to increase above the plateau level for 10 minutes after phenylephrine administration (10 microg/kg) and for 30 minutes after furosemide administration (1,000 microg/kg). In the phenylephrine group, the UF resumed when the IUP reached 75.8 mm Hg, and thereafter the IUP gradually decreased in parallel with the increase in the UF. From these results, we conclude that in dogs, CL-316243 reduces the IUP by allowing the UF to resume as a result of a relaxation of ureter at the obstruction site, whereas with phenylephrine, the reduction in the IUP is secondary to a resumption in the UF resulting from an induced contraction of ureter that causes an increase in hydrostatic pressure above the obstruction site.

Systemic and topical drug administration in the pig ureter: effect of phosphodiesterase inhibitors alpha1, beta and beta2-adrenergic receptor agonists and antagonists on the frequency and amplitude of ureteral contractions

PURPOSE

We searched for compounds that are pharmacologically active on ureteral motility for treating ureteral colic to ease retrograde access into the ureter and improve the clearance of stones or stone particles from the ureter. The effects of the alpha1-adrenergic receptor agonist phenylephrine, the nonselective beta and beta2-adrenergic receptor agonists isoproterenol and fenoterol, and the phosphodiesterase inhibitors papaverine (nonspecific) and rolipram (type IV) on the frequency and amplitude of ureteral contractions when administered intravenously or topically were investigated in pigs.

MATERIALS AND METHODS

A total of 52 pigs were anesthetized. A double lumen 6Fr catheter was inserted through each renal pelvis and into the ureter, allowing perfusion of saline or drug solution into the renal pelvis and the recording of contractions from the mid portion of the ureter.

RESULTS

The alpha1 and beta-adrenergic receptors of the ureter are not tonically activated by endogenous epinephrine or norepinephrine. Phenylephrine administered intravenously at a dose of 0.01 to 3 mg./kg. and topically at 0.1 to 3 mg./ml. per minute increased contraction frequency 10 and 4-fold, respectively, and contraction amplitude 2-fold each in a dose dependent manner. Arterial blood pressure increased markedly during intravenous administration of phenylephrine but was minimally affected during topical application. The phenylephrine effects were reversed by the antagonist prazosin. Isoproterenol administered intravenously at a dose of 0.01 to 10 mg./kg. and topically at 0.1 to 200 microg./ml. per minute decreased contraction frequency to 13% and 31% of controls, respectively. Contraction amplitude was not affected by intravenous administration but decreased to 59% of controls when applied topically. These effects were also observed with a slight delay in the saline perfused contralateral ureter. The heart rate also increased, suggesting absorption of the drug by the urothelium. The isoproterenol effects were blocked by the antagonist propranolol. Fenoterol administered intravenously at a dose of 0.1 to 30 microg./kg. and topically at 0.003 to 1 mg./ml. per minute decreased contraction frequency to 14% and 10% of controls, and contraction amplitude to 84% and 65%, respectively. These effects on the drug perfused ureter were also observed on the contralateral saline perfused ureter but to a lesser extent. The fenoterol effects were blocked by the antagonist propranolol. Papaverine administered intravenously at a dose of 0.001 to 3 mg./kg. decreased contraction frequency to 33% of controls. Topically administered papaverine as well as intravenous and topically administered rolipram had no relevant effect on ureteral motility.

CONCLUSIONS

Intravenous phenylephrine increases, and isoproterenol and fenoterol decrease the frequency and amplitude of ureteral contractions in the pig. The same effects are observed with the topical administration of phenylephrine, which causes a significant local but not systemic side effect. Topical administration of isoproterenol and fenoterol produced local as well as systemic effects, suggesting absorption by the urothelium. However, to our knowledge a drug that relaxes ureteral peristalsis in pigs without causing systemic side effects has not yet been identified.

Evaluation of ureteric contraction: a comparison among ring, spiral-cut and longitudinal segments

OBJECTIVE

To determine the optimal contractile response of isolated ureters to inflammatory mediators and neurotransmitters by evaluating four common methods of ureteric suspension.

MATERIALS AND METHODS

Ureters from adult domestic swine were placed immediately in Krebs buffer and cut into 4-5 mm segments. Four methods of suspension were compared: (i) an unopened ring segment suspended horizontally; (ii) a spirally cut segment (lumen cut open at a 45 degrees and suspended end-to-end); (iii) an open longitudinal segment; and (iv) a closed longitudinal segment. All segments were placed in individual water-jacketed tissue baths containing Krebs buffer, the frequency of contraction measured using a force transducer and registered on a polygraph. The sensitivity of all four segments was tested by measuring the tension and frequency in response to increasing frequencies of electric field stimulation, and by a cumulative concentration-response curve to carbachol.

RESULTS

Ureteric segments responded with an increased frequency of contraction depending on the intensity of stimulus to both electric field stimulation and carbachol. However, there were no significant differences in spontaneous levels of contraction, sensitivity or maximal response among the methods of suspension in response to electric field stimulation or carbachol.

CONCLUSION

These results indicate that all four methods of suspending the ureteric segments produce contractile responses sensitive enough to study the action of various neurotransmitters.

Beta-adrenoceptor subtypes in the ureteral smooth muscle of rats, rabbits and dogs

We investigated the beta-adrenoceptor subtypes mediating ureteral relaxation in rats, rabbits and dogs. The relaxing effects of beta-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 beta1-adrenoceptor agonist, dobutamine, produced relaxation of rat ureter. The beta2-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-b enzodioxole-2,2-dicarboxylate] and CGP-12177A [(+/-)[4-[3[(1,1-dimethylethyl)amino]-2-hydroxypropoxy]-1,3-dihydro-2H-+ ++benzimidazol-2-one hydrochloride], beta3-adrenoceptor agonists, were more effective in relaxing canine ureter than were dobutamine and procaterol. Isoprenaline-induced relaxation was antagonized by a beta1-adrenoceptor antagonist, CGP-20712A [2-hydroxy-5(2-((2-hydroxy-3-(4-((1-methyl-4-trifluoromethyl)1H-imidazol e-2-yl)phenoxy)propyl)amino)ethoxy)-benzamide monomethane sulphonate], in rats and by a beta2-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 beta-adrenoceptor antagonist, bupranolol, antagonized isoprenaline-induced relaxation in all species tested. In conclusion, beta-adrenoceptor agonists may relax ureter by stimulating mainly beta1-adrenoceptors in rats, beta2-adrenoceptors in rabbits and mainly beta3-adrenoceptors in dogs.

Characterization of histamine receptors in the ureter of the dog

We investigated the effects of histamine on the motility of isolated segments from canine ureters and characterized pharmacologically the histamine receptors involved. We also evaluated the effects of various autacoids (5-HT, carbachol, noradrenaline, thromboxane, prostaglandin F2alpha) on the motility of canine ureters. Histamine as well as the H1 receptor agonist 2-(2-pyridyl)ethylamine elicited a concentration-dependent contraction. This contractile response was antagonized by dimethindene, causing a rightward shift (pA2 8.30) and a reduction of the slope and the maximal effect (pD'2 6.01) of the concentration-response curve. The histamine H2 receptor antagonist cimetidine in a concentration of 10(-5) mol/l was ineffective concerning the concentration-response curve for histamine. After precontraction of the ureter segments (5-HT, carbachol, prostaglandin F2alpha), a concentration-dependent relaxant effect was evaluated in the presence of histamine or the histamine H2 receptor agonist impromidine. The histamine H2 receptor antagonist cimetidine attenuated the relaxant response, causing a rightward shift of the concentration-response curve. All autacoids except thromboxane were capable of increasing contractility in canine ureters. Comparing the absolute contractile force in the presence of prostaglandin F2alpha, 5-HT, carbachol, noradrenaline and potassium, we found that histamine exhibits the most marked effect on this parameter in the canine ureter. It is concluded that there are two types of histamine receptors modulating contractile activity in the canine ureter: histamine H1 receptors, which mediate contraction, and histamine H2 receptors, which mediate relaxation (in the precontracted tissue).