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

Detection of muscarinic receptor subtypes in human urinary bladder mucosa: age and gender-dependent modifications

AIMS

Muscarinic receptor subtypes expressed in the human urinary bladder mucosa were characterized, investigating whether there were gender-dependent differences and if aging could induce changes in their expression.

METHODS

The study was carried out on 34 subjects, 22 men and 12 women, divided in four groups, based on gender and age. Gene expression was evaluated by quantitative RT-PCR. The Western blot was performed using the 4-12% NuPAGE Bis-Tris Gel System.

RESULTS

The molecular expression of each subtype of the M(1) receptor family was observed and it was not influenced either by gender or age. M(2) receptor family transcripts revealed that both M(2) and M(4) were detected and that the M(2) transcripts were modified by both gender and age. Indeed, M(2) mRNA was lower in old rather than adult men (P < 0.05), but higher in rather old than adult women (P < 0.05). Further, adult men expressed more M(2) mRNA than adult women (P < 0.05), while the opposite was detected in old age (P < 0.05). The Western blot followed by quantification confirmed that the mRNAs were translated into proteins, and that the M(2) subtype showed similar modifications found at molecular level.

DISCUSSION

The selective modification of M(2) receptors observed at the urinary bladder mucosa levels indicates that this anatomical structure could play an active role in the pathophysiology of micturition and supports evidence suggesting an effect of antimuscarinic drugs at this level. Whether these results may influence the age-dependent development of micturition disorders remains to be determined.

[Ureter drugs]

Many improvements have been made recently in the field of the ureteral smooth muscle pharmacology. After a brief summary on physiological basis, we review what is known about effects on ureter of different drugs class. In a second part, we review clinical applications for renal colic analgesia, calculi expulsive medical therapy, ESWL adjuvant treatment and preoperative treatment before retrograde access. There are now sufficient data on NSAID and alpha-blockers. beta-agonists, especially for beta3 selective ones, and topical drugs before retrograde access are interesting and should be further evaluated.

Effectiveness of Low-dose and Standard-dose Tamsulosin in the Treatment of Distal Ureteric Stones: A Randomized Controlled Study

Low-dose (0.2 mg/day) and standard-dose (0.4 mg/day) tamsulosin were studied in a randomized controlled trial of 75 outpatients with distal ureteroliths in Thailand. Group 1 ( n = 25; control) received oral sodium diclofenac 50 mg twice a day for 10 days; group 2 ( n = 25) received oral sodium diclofenac 50 mg twice a day for 10 days, with oral tamsulosin 0.2 mg once a day up to 28 days; and group 3 ( n = 25) received oral sodium diclofenac 50 mg twice a day for 10 days, with oral tamsulosin 0.4 mg once a day up to 28 days. For groups 1, 2 and 3, respectively, the expulsion rates were 4%, 40% and 68% (significantly different for group 1 vs group 2, and for group 1 vs group 3) and mean expulsion times were 23.00, 9.30 and 10.76 days. Both doses of tamsulosin increased stone expulsion rate and decreased expulsion time in comparison with the control, and have been shown to be safe and effective in Asian patients.

Efficacy of Tamsulosin with Extracorporeal Shock Wave Lithotripsy for Passage of Renal and Ureteral Calculi

Objective:

To review the evidence for the safety and efficacy of adjunctive tamsulosin in enhancing the efficacy of renal and ureteral stone clearance when used with extracorporeal shock wave lithotripsy (ESWL).

Data Sources:

A search of MEDLINE (1950-January 2008), PubMed (1950-January 2008), and the Iowa Drug Information System (1966-January 2008) was performed using the search terms tamsulosin and extracorporeal shock wave lithotripsy. MeSH headings included lithotripsy and adrenergic α-antagonists. Additional references were found by searching bibliographic references of resulting citations.

Study Selection and Data Extraction:

All studies utilizing tamsulosin therapy after a single session of ESWL or after the development of steinstrasse, an accumulation of stone fragments that obstructs the ureter, were included.

Data Synthesis:

To date, 5 prospective studies have evaluated the efficacy of tamsulosin combined with ESWL in enhancing the passage of renal and ureteral stones. in one trial, 12-week renal stone clearance was 60% in the control group compared with 78.5% in the tamsulosin group (p = 0.037). Among trials that evaluated overall ureteral stone clearance, efficacy rates were 33.3-79.3% in the control groups compared with 66.6-96.6% in the tamsulosin groups. Reports of pain and supplemental analgesic dosing were consistently lower with tamsulosin, but data on the incidence of subsequent retreatment with ESWL or ureteroscopy was rarely reported. Adjunctive tamsulosin particularly enhanced the passage of renal stones 10-24 millimeters in diameter. Overall, tamsulosin was well tolerated.

Conclusions:

Overall, evidence suggests that adjunctive tamsulosin therapy combined with ESWL is safe and effective in enhancing stone clearance in patients with renal stones 10-24 millimeters in diameter. Evidence regarding ureteral stone clearance is inconclusive, although adjunctive tamsulosin has been reported to reduce painful episodes. Larger prospective trials evaluating different dosages and stone locations, as well as the ability of tamsulosin to reduce repeat ESWL or more invasive methods such as ureteroscopy should be performed.

Cost-Effectiveness of Medical Expulsive Therapy Using Alpha-Blockers for the Treatment of Distal Ureteral Stones

OBJECTIVE

Medical expulsive therapy (MET) has recently emerged as an efficacious and safe option for the initial management of ureteral stones. The objective of this study was to assess the cost-effectiveness of MET compared with conservative therapy for the treatment of ureteral stones using international cost data from the United States and four European countries.

MATERIAL AND METHODS

A decision analysis model was built with the use of TreeAge Pro 2004 software with linear success rate assumptions. The likelihood of spontaneous passage of ureteral stones according to their size and location was estimated with the use of data derived from a published meta-analysis. The estimated cost of ureteroscopy (URS) in the United States ($4973) was based on the mean cost of 121 consecutive cases performed at a large metropolitan hospital. URS costs for other countries were obtained from a published international survey. The cost of tamsulosin ($2.08 per day), currently the most commonly used medical expulsive agent, was estimated as a mean of the costs obtained from two national pharmacy chains. MET and conservative therapies were compared with the use of one-way and two-way sensitivity analyses.

RESULTS

In the United States, MET using tamsulosin resulted in a $1132 cost advantage over observation. MET maintained its cost advantage even in countries where the cost of URS is much lower than in the United States. Two-way sensitivity analysis showed that MET remained cost-effective even with very low rates of spontaneous passage, minimal benefit of MET, or low cost of URS.

CONCLUSION

MET is a cost-effective strategy for the management of distal ureteral stones--even those with a low rate of spontaneous passage--providing another incentive for initial "facilitated observation" before embarking on surgical intervention.

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.

Doxazosin relaxes ureteral smooth muscle and inhibits epinephrine-induced ureteral contractility in vitro

OBJECTIVES

Although recent evidence has supported increased ureteral stone passage with selective alpha(1)-adrenergic receptor antagonists, no mechanistic study evaluating ureteral relaxation by alpha(1) antagonism has been reported to date. We evaluated whether the alpha-blocker doxazosin reduces spontaneous, and inhibits alpha(1)-agonist-induced ureteral contractility. Additionally, alpha-receptor subtypes in normal and obstructed human ureter were analyzed.

METHODS

We exposed porcine ureters in organ tissue baths with 0.1, 1.0, or 10 microM doxazosin and recorded the tension for 90 minutes. After the initial treatment, a concentration-response curve of epinephrine or phenylephrine (1 nM to 10 microM) was generated. The experiment was repeated with the proximal, mid-, and distal ureter. The relative expression of the alpha 1A, 1B, and 1D receptor subtypes in normal and obstructed human ureters was analyzed using immunoblotting.

RESULTS

Doxazosin reduced the spontaneous ureteral contractility rates in a concentration-dependent fashion by 23% to 34%. A more pronounced relaxation effect by doxazosin was evident when epinephrine was introduced to the tissues. In 1 and 10-microM doxazosin-pretreated tissues, epinephrine caused 89% and 100% relaxation, respectively. Phenylephrine-induced contractions were antagonized by doxazosin but not reversed to any relaxant function. No differential expression of alpha(1)-receptor subtypes was identified in the obstructed versus normal ureters.

CONCLUSIONS

The results of our study have shown that alpha(1)-receptor blockade decreases ureteral contractility and inverses the effect of epinephrine, providing even greater relaxation. We hypothesize that alpha receptor blockade might relax the ureter and induce stone passage by way of epinephrine activation of beta receptors. Additional studies should be performed to validate this hypothesis and to compare various alpha(1)-receptor subtype antagonists.

Ureteric colic: new trends in diagnosis and treatment

The diagnostic approach to ureteric colic has changed due to the introduction of new radiological imaging such as non-contrast CT. The role of intravenous urography, which is regarded as the gold standard for the diagnosis of ureteric colic, is being challenged by CT, which has become the first-line investigation in a number of centres. The management of ureteric colic has also changed. The role of medical treatment has expanded beyond symptomatic control to attempt to target some of the factors in stone retention and thereby improve the likelihood of spontaneous stone expulsion.

Expressions and mechanical functions of α1-adrenoceptor subtypes in hamster ureter

We characterized the alpha(1)-adrenoceptor subtypes in hamster ureters according to gene and protein expressions and contractile function. Real-time quantitative reverse-transcription polymerase chain reaction and immunohistochemical analysis were performed to determine mRNA levels and receptor protein expressions respectively, for alpha(1A)-, alpha(1B)- and alpha(1D)-adrenoceptors in hamster ureteral smooth muscle. alpha(1)-Adrenoceptor antagonists were tested against the phenylephrine (alpha(1)-adrenoceptor agonist)-induced contraction in isolated hamster ureteral preparations using a functional experimental approach. In the smooth muscle, relative mRNA expression levels for alpha(1a)-, alpha(1b)- and alpha(1d)-adrenoceptors were 10.7%, 1.2% and 88.1%, respectively, and protein expressions were identified for alpha(1A)- and alpha(1D)-adrenoceptors immunohistochemically. Noradrenaline and phenylephrine (alpha(1)-adrenoceptor agonist) each produced a concentration-dependent tonic contraction, their pD(2) values being 6.87+/-0.08 and 6.10+/-0.05, respectively. Prazosin (nonselective alpha(1)-adrenoceptor antagonist), silodosin (selective alpha(1A)-adrenoceptor antagonist) and BMY-7378 (8-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-8-azaspiro[4.5]decane-7,9-dione dihydrochloride) (selective alpha(1D)-adrenoceptor antagonist) competitively antagonized the phenylephrine-induced contraction (pA(2) values, 8.60+/-0.07, 9.44+/-0.06 and 5.75+/-0.07, respectively). Chloroethylclonidine (3x10(-6) mol/L or more) produced a rightward shift in the concentration-response curve for phenylephrine. Thus, in hamster ureters, alpha(1A)- and alpha(1D)-adrenoceptors were more prevalent than the alpha(1B)-adrenoceptor, with contraction being mediated mainly via alpha(1A)-adrenoceptors. If these findings hold true for humans, alpha(1A)-adrenoceptor antagonists could become useful medication for stone passage in urolithiasis patients.

Examination of alpha 1 adrenoceptor subtypes in the human ureter

AIM

Urinary stone disease is a common condition affecting up to 12% of the population. Speedy elimination of ureterolithiasis in the lower part of ureters is reported with the alpha 1-blocker. This study was carried out to characterize the alpha 1 adrenoceptors (AR) subtype gene and protein expression in the proximal, medial, and distal regions of the human ureter with the aim of facilitating stone expulsion.

METHODS

The study was carried out on 20 volunteers. Proximal, medial and distal ureter specimens were obtained as discarded tissues after nephroureterectomy for renal pelvic or ureteral carcinoma. Proximal ureter specimens were obtained as discarded tissues after nephrectomy for renal carcinoma. Using ureter samples, real-time reverse transcription polymerase chain reaction (RT-PCR) and immunohistochemical staining were performed.

RESULTS

The alpha 1d subtype mRNA was highly expressed in each ureteral region, accounting for about 54% of the total AR Messenger Ribonucleic Acid. In the proximal and medial ureter, the distribution of ARs was alpha 1d > or = alpha 1a > alpha 1b as well as that of the total ureter. The distal ureter expressed the highest amount of alpha 1d ARs. The alpha 1d subtype expression tended to be high compared with the alpha 1a subtype expression. In the distal ureter, the distribution of ARs was alpha 1d > alpha 1a > alpha 1b. Immunohistochemical staining revealed that expressions of alpha 1a-AR and alpha 1d-AR were higher than that of alpha 1b-AR.

CONCLUSIONS

According to our results, we should try the alpha 1d AR antagonist for the conservative expulsive therapy of distal ureteral stones in the highest region of alpha 1d subtype distribution.

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.

Is There a Role for Tamsulosin in Shock Wave Lithotripsy for Renal and Ureteral Calculi?

PURPOSE

We evaluated the effect of the alpha-blocker tamsulosin on stone clearance, analgesic requirements and steinstrasse in shock wave lithotripsy for solitary renal and ureteral calculus.

MATERIALS AND METHODS

A prospective, double-blind, randomized placebo controlled study was performed during 1 year involving 60 patients with a solitary renal or ureteral calculus undergoing shock wave lithotripsy. The control group (30) received 0.4 mg tamsulosin and the study group (30) received placebo daily until stone clearance or for a maximum of 30 days. An oral preparation of dextropropoxyphene hydrochloride and acetaminophen was the analgesic used on an on-demand basis. The parameters assessed were stone size, position, clearance time, effect on steinstrasse and analgesic requirement.

RESULTS

The overall clearance rate was 96.6% (28 of 29) in the study group and 79.3% (23 of 29) in the control group (p = 0.04). With larger stones 11 to 24 mm the difference in the clearance rate was significant (p = 0.03) but not so with the smaller stones 6 to 10 mm (p = 0.35). The average dose of analgesic used was lower with tamsulosin than with controls, without statistical significance. Steinstrasse resolved spontaneously in the tamsulosin group whereas 25% (2 of 8) required intervention in the placebo group. There was no difference between the 2 groups with regard to age, stone size or location.

CONCLUSIONS

The alpha-blocker tamsulosin seemed to facilitate stone clearance, particularly with larger stones during shock wave lithotripsy for renal and ureteral calculus. It also appeared to improve the outcome of steinstrasse. Tamsulosin may have a potential role in routine shock wave lithotripsy.

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.

Medical therapy to facilitate urinary stone passage: a meta-analysis

BACKGROUND

Medical therapies to ease urinary-stone passage have been reported, but are not generally used. If effective, such therapies would increase the options for treatment of urinary stones. To assess efficacy, we sought to identify and summarise all randomised controlled trials in which calcium-channel blockers or alpha blockers were used to treat urinary stone disease.

METHODS

We searched MEDLINE, Pre-MEDLINE, CINAHL, and EMBASE, as well as scientific meeting abstracts, up to July, 2005. All randomised controlled trials in which calcium-channel blockers or alpha blockers were used to treat ureteral stones were eligible for inclusion in our analysis. Data from nine trials (number of patients=693) were pooled. The main outcome was the proportion of patients who passed stones. We calculated the summary estimate of effect associated with medical therapy use using random-effects and fixed-effects models.

FINDINGS

Patients given calcium-channel blockers or alpha blockers had a 65% (absolute risk reduction=0.31 95% CI 0.25-0.38) greater likelihood of stone passage than those not given such treatment (pooled risk ratio 1.65; 95% CI 1.45-1.88). The pooled risk ratio for alpha blockers was 1.54 (1.29-1.85) and for calcium-channel blockers with steroids was 1.90 (1.51-2.40). The proportion of heterogeneity not explained by chance alone was 28%. The number needed to treat was 4.

INTERPRETATION

Although a high-quality randomised trial is necessary to confirm its efficacy, our findings suggest that medical therapy is an option for facilitation of urinary-stone passage for patients amenable to conservative management, potentially obviating the need for surgery.

Cólico renal: Revisión de la literatura y evidencia científica

In recent years diagnosis and treatment of acute renal colic have changed thanks to the introduction of new radiological procedures that allow with high reliability to establish obstructive cause and a better treatment. In the other hand, there are multiple clinical studies that show the most effective treatments for acute crisis. The aim of this revision is to update the diagnostic and therapeutic aspects of renal colic which were modified recently, and allowed to break some classic concepts without scientific evidence.