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

In vitro effects of β3-adrenoceptor agonist mirabegron on the human ureter

INTRODUCTION

This study aimed to investigate the effect of mirabegron, a β3-adrenoceptor agonist with widespread clinical use for treating overactive bladder disease, on isolated healthy human ureter strips.

MATERIALS AND METHODS

This was a prospective study employing a series of in vitro organ bath experiments using ureteral tissues of kidney grafts from 10 healthy donors. The ureteral strips were subjected to cumulative mirabegron concentrations (10-9-10-4.5 M). Effects on frequency or amplitude of spontaneous, 10 mM KCl- or EFS-induced contractions were evaluated.

RESULTS

Mirabegron decreased the frequency of spontaneous ureteric contraction in a concentration-dependent manner. Statistically significant decrease in the frequency of spontaneous contraction was observed at 10-8-10-4.5 M. In 10 mM KCl medium, statistically significant change in frequency was observed at 10-9-10-4.5 M. Statistically significant decrease in the amplitudes of spontaneous contraction was observed at 10-7-10-4.5 M. In a 10 mM KCl medium, statistically significant change in amplitudes was observed at 10-8-10-4.5 M.

CONCLUSIONS

Mirabegron reduced the amplitude and frequency of human ureter activity in in vitro organ bath studies. This effect was achieved in a dose-dependent manner on isolated tissue strips. Although monotherapy with mirabegron remains uncertain, this study has the potential to elucidate the mechanism underlying the effectiveness of mirabegron, particularly in combination therapy for ureteral stones.

Pharmacological Modulation of Intrarenal Pressure in a Porcine Model Using a Novel Isoprenaline-Eluting Guidewire

Introduction: Several complications of retrograde intrarenal surgery have been attributed to inadvertent increases in intrarenal pressure. We recently described the development of an innovative isoprenaline-eluting guidewire (IsoWire). The objective of this study was to investigate the impact of this IsoWire on the intrarenal pressure and evaluate its safety. Materials and Methods: This study was performed in 17 renal units using a porcine model. As controls, the intrarenal pressure, heart rate, and mean arterial pressure were measured for a duration of six minutes with a standard guidewire placed in the renal pelvis. For the experiment, the conventional guidewire was substituted with the IsoWire and the same parameters were measured. Blood samples were taken at one-minute intervals to measure plasma isoprenaline levels. This procedure was repeated on the opposite side. Results: The mean intrarenal pressure reduction was 29% (95% CI: 13%-53%). The mean isoprenaline effect time was 174 seconds. No changes in heart rate (p = .908) or mean arterial pressure (p = .749) were recorded after IsoWire insertion. Plasma isoprenaline levels were below the quantitation threshold. Isoprenaline concentrations in the plasma were below the quantification threshold. Ureteroscopy revealed no ureteral lesions. Conclusions: The IsoWire demonstrated a safe and effective reduction of intrarenal pressure. Additional research is necessary to determine whether ureteral smooth muscle relaxation generated by isoprenaline facilitates easier insertion of a ureteral access sheath, decreases the incidence of ureteral access sheath related ureteral lesions, or even encourage the practice of sheathless retrograde intrarenal surgery.

Introducing an lsoprenaline Eluting Guidewire: Report on its Design and the Results of the Dose-Determining Pilot Study

Introduction: Retrograde intrarenal surgery (RIRS) is associated with complications, many of which are related to the intrarenal pressure (IRP). We aim to describe the design of a novel isoprenaline-eluting guidewire ("IsoWire") and present the results from the first in vitro release studies and the first animal studies showing its effect on IRP. Materials and Methods: The IsoWire comprises a Nitinol core surrounded by a stainless-steel wire wound into a tight coil. The grooves created by this coil provided a reservoir for adding a hydrogel coating into which isoprenaline, a beta-agonist, was loaded. Animal studies were performed using a porcine model. For the control, IRP, heart rate (HR), and mean arterial pressure (MAP) were measured continuously for 6 minutes with a standard guidewire in place. For the experiment, the standard hydrophilic guidewire was removed, the IsoWire was inserted into the renal pelvis, and the same parameters were measured. Results: In vitro analysis of the isoprenaline release profile showed that most (63.9 ± 5.9%) of the loaded drug mass was released in the 1st minute, and almost all of the drug was released in the first 4 minutes exponentially. Porcine studies showed a 25.1% reduction in IRP in the IsoWire that released 10 μg in the 1st minute; however, there was a marked increase in HR. The average percentage reduction in IRP was 8.95% and 21.3% in the IsoWire that released 5 and 7.5 μg of isoprenaline, respectively, with no changes in HR or MAP. Conclusions: The IsoWire, which releases 5 and 7.5 μg of isoprenaline in the 1st minute, appears to be safe and effective in reducing the IRP. Further studies are needed to establish whether the isoprenaline-induced ureteral relaxation will render easier insertion of a ureteral access sheath, reduce IRP during sheathless RIRS, or even promote the practice of sheathless RIRS.

Adrenoceptors in the Lower Urinary Tract

Adrenoceptors importantly contribute to the physiological regulation of lower urinary tract (LUT) function and have become a target of several clinically successful treatments for major LUT diseases. In the bladder dome, β-adrenoceptor subtypes are found in multiple cell types and mediate relaxation of detrusor smooth muscle, perhaps partly indirectly by acting on afferent nerves and cells of the mucosa. β₃-adrenoceptor agonists such as mirabegron and vibegron are used to treat overactive bladder syndrome. In the bladder trigone and urethra, α₁-adrenoceptors cause contraction and thereby physiologically contribute to bladder outlet resistance. α₁-adrenoceptors in the prostate also cause contraction and pathophysiologically elevate bladder outlet resistance leading to voiding dysfunction in benign prostatic hyperplasia. α₁-adrenoceptor antagonist such as tamsulosin is widely used as a first-line option to treat LUT symptoms in men, but it remains unclear to which extent and how smooth muscle relaxation contributes to symptom relief.

Intravesical aminophylline instillation as an alternative for balloon dilatation prior to semi-rigid ureteroscopic management of distal ureteral stones

Purpose

In a randomized controlled trial, we evaluated the effect of intravesical aminophylline instillation (IVAI) on intraureteral pressure of lower ureter and its use as an alternative to balloon dilatation after failure of advancing semi-rigid ureteroscope through the ureteric orifice without endodilatation.

Methods

Our study included 83 patients with juxta-vesical distal ureteral calculi requiring endodilatation after unsuccessfully introducing the semi-rigid ureteroscope through the ureteric orifice. Patients were randomized into two groups: group A (study group) included 41 patients, where IVAI was used to dilate the ureter and facilitate ureteroscopy (the intraureteral pressure was measured using a pressure transducer connected to an invasive pressure monitor before and 5 min after IVAI), whereas group B (control group) included 42 patients, where balloon dilatation was used prior to ureteroscopy. Perioperative surgical outcomes of ureteroscopy were evaluated in both groups.

Results

A statistically significant decrease in mean intraureteral pressure of intravesical ureter was found after IVAI from 12.34 mmHg ± 1.94 before injection to 8.46 mmHg ± 1.94 after injection (P < 0.001). Ureteral injuries, postoperative pain and hematuria were statistically significantly less among the study group compared to the control group (P < 0.05). We did not find statistically significant differences in operative time, need for DJ ureteral stenting or stone-free rate between both groups and no perioperative side effects were associated with IVAI.

Conclusion

In ureteroscopic management of distal ureteral stones, intravesical aminophylline instillation is safe, inexpensive and effective in reducing intraureteral pressure and achieves comparable outcomes to balloon dilatation with less ureteral injuries, postoperative pain and hematuria.

Salbutamol for analgesia in renal colic: study protocol for a prospective, randomised, placebo-controlled phase II trial (SARC)

BACKGROUND

Renal colic is the pain experienced by a patient when a renal calculus (kidney stone) causes partial or complete obstruction of part of the renal outflow tract. The standard analgesic regimes for renal colic are often ineffective; in some studies, less than half of patients achieve complete pain relief, and a large proportion of patients require rescue analgesia within 4 h. Current analgesic regimes are also associated with significant side effects including nausea, vomiting, drowsiness and respiratory depression. It has been hypothesised that beta adrenoreceptor agonists, such as salbutamol, may reduce the pain of renal colic. They have been shown to impact a number of factors that target the physiological causes of pain in renal colic (ureteric spasm and increased peristalsis, increased pressure at the renal pelvis and prostaglandin release with inflammation). There is biological plausibility and a body of evidence sufficient to suggest that this novel treatment for the pain of renal colic should be taken to a phase II clinical trial. The aim of this trial is to test whether salbutamol is an efficacious analgesic adjunct when added to the standard analgesic regime for patients presenting to the ED with subsequently confirmed renal colic.

METHODS

A phase II, randomised, placebo-controlled trial will be performed in an acute NHS Trust in the East Midlands. Patients presenting to the emergency department with pain requiring IV analgesia and working diagnosis of renal colic will be randomised to receive standard analgesia ± a single intravenous injection of Salbutamol. Secondary study objectives will explore the feasibility of conducting a larger, phase III trial.

DISCUSSION

The trial will provide important information about the efficacy of salbutamol as an analgesic adjunct in renal colic. It will also guide the development of a definitive phase III trial to test the cost and clinical effectiveness of salbutamol as an analgesic adjunct in renal colic. Salbutamol benefits from widespread use across the health service for multiple indications, extensive staff familiarity and a good side effect profile; therefore, its potential use for pain relief may have significant benefits for patient care.

TRIAL REGISTRATION

ISRCTN Registry ISRCTN14552440 . Registered on 22 July 2019.

Mirabegron in medical expulsive therapy for distal ureteral stones: a prospective, randomized, controlled study

OBJECTIVE

To observe the efficacy and safety of Mirabegron in patients with distal, ureteral stones ≤ 10 mm.

PATIENTS AND METHODS

A total of 90 patients with distal ureteral stones ≤ 10 mm were prospectively randomized into two groups. Forty-five cases in the study group and 45 cases as control. The stone-free rates (SFRs) and renal colic episodes between two groups were compared at the 1st, 2nd and 4th week end by imaging examinations.

RESULT

All of 90 patients were randomly assigned to two groups. In patients with ≤ 5 mm stones, the SFRs in the 1st week (63.6% vs. 33.3%, P = 0.040), the 2nd week (86.4% vs. 54.2%, P = 0.018), and the 4th week (90.9% vs. 66.7%, P = 0.046) after treatment were all significantly higher than that in the control group by the stratification analysis of stone size. Even though SFRs were all higher for patients with > 5 mm stones in study group, there was no statistically significant difference (All P > 0.05). In terms of renal colic episodes, the frequency of occurrence of the study group was significantly lower than that of the control group and need less antalgic.

CONCLUSIONS

The MET with Mirabegron has a significant role in improve SFR for the patients with distal ureteral stones ≤ 5 mm and no effect in > 5 mm stones. Furthermore, Mirabegron reduces the need for antalgic in ≤ 10 mm stones with low incidence of adverse effects.

Risks of flexible ureterorenoscopy: pathophysiology and prevention

Currently, indications for flexible ureterorenoscopy (fURS) are expanding, mainly due to technological advancements. Although data from clinical series definitely presents fURS as a safe procedure, serious complications including sepsis and ureteral lesions do occur. These complications seem to be a result of the unique elements of fURS, ureteral access and irrigation, pushing normal upper urinary tract physiology into pathophysiological processes, including intrarenal/pyelo-veneous backflow and ureteral contractions, potentially resulting in septic, haemorrhagic and ureteral lesional complications. Knowledge on normal upper urinary tract physiology are crucial for understanding how these harmful effects of fURS may be avoided or minimized. The pathophysiology of intrarenal pressure increases and ureteral access will be discussed as a basis for understanding preventive measures. Role of antibiotics, ureteral access sheaths, safty guidewires, pain medication, prestenting and pharmacologic modulation of pyeloureteral dynamics are reviewed from a pathophysiological perspective.

Pathophysiological aspects of ureterorenoscopic management of upper urinary tract calculi

PURPOSE OF REVIEW

Indications for ureterorenoscopy are expanding without hard scientific evidence to support its efficacy. Therefore, it is extremely important to focus on potential harmful effects of the procedure itself. This review explores how physiology of the upper urinary tract reacts to ureterorenoscopy, potentially translating into harmful effects, and how such pathophysiological processes may be minimized.

RECENT FINDINGS

Complications to ureterorenoscopy and postoperative pain seem to be related to intrarenal pressure and/or access. Mean intrarenal pressures in the range of 60-100 mmHg during ureterorenoscopy without access sheaths have been measured, thus by far exceeding the threshold for intrarenal backflow, potentially resulting in septic complications. Intrarenal pressure may be reduced by use of ureteral access sheaths, which, however, may cause ureteral damage due to the limited size of the ureter and strain-induced ureteral contractions (peristalsis). Different receptor types modulate this peristaltic activity. β-receptor agonists have been investigated in animal and human trials for the purpose of relaxing the ureter. In randomized, placebo-controlled trials in pigs and humans, usage of the β-receptor agonist isoproterenol in the irrigation fluid has shown a potential for reducing both intrarenal pressure and ureteral tone during ureterorenoscopy.

SUMMARY

Upper urinary tract physiology has unique features that may be pushed into pathophysiological processes by the unique elements of ureterorenoscopy: access and irrigation. Pharmacological ureteral relaxation during ureterorenoscopy deserves further attention with regard to reducing complications and postoperative pain.

β-Adrenoreceptor agonists in the management of pain associated with renal colic: a systematic review

OBJECTIVES

To determine whether β-adrenoreceptor agonists are effective analgesics for patients with renal colic through a systematic review of the literature.

SETTING

Adult emergency departments or acute assessment units.

PARTICIPANTS

Human participants with proven or suspected renal colic.

INTERVENTIONS

β-adrenoreceptor agonists.

OUTCOME MEASURES

Primary: level of pain at 30 min following administration of the β-agonist. Secondary: level of pain at various time points following β-agonist administration; length of hospital stay; analgesic requirement; stone presence, size and position; degree of hydronephrosis.

RESULTS

256 records were screened and 4 identified for full-text review. No articles met the inclusion criteria.

CONCLUSIONS AND IMPLICATIONS

There is no evidence to support or refute the proposed use of β-agonists for analgesia in patients with renal colic. Given the biological plausibility and existing literature base, clinical trials investigating the use of β-adrenoreceptor agonists in the acute setting for treatment of the pain associated with renal colic are recommended.

TRIAL REGISTRATION NUMBER

CRD42015016266.

Verapamil Inhibits the Pelvic Pressure Increase Corresponding to Flow Perfusion in the Porcine Percutaneous Renal Puncture Model

PURPOSE

To estimate the effects of verapamil on pelvic pressure and investigate the possible systemic side effects in the porcine model during the procedure of increasing perfusion rates.

MATERIALS AND METHODS

In the experimental group, the pelvic pressure was recorded with increasing perfusion rates of the renal pelvis (0, 2, 4, 6, 8, 10, 14 and 20 ml/min) in response to intraluminal administration of increasing concentrations of verapamil (0, 0.1, 1, 10 and 100 µg/ml) in isotonic saline. In the isotonic saline group, the pressure flow study was also done by increasing perfusion rates of the renal pelvis per animal using isotonic saline without verapamil.

RESULTS

Perfusion with 1, 10 and 100 µg/ml verapamil caused a decrease in pelvic pressure as a response to increasing flow rates, whereas perfusion with 0.1 µg/ml verapamil did not obviously inhibit the increase of pelvic pressure at all perfusion rates compared with other concentrations. Importantly, the mean systolic blood pressure and mean heart rate were stable despite the increase of flow rates and verapamil concentrations. In the isotonic saline group, perfusion with isotonic saline resulted in an increase in the pelvic pressure with an increase in flow rates each time.

CONCLUSIONS

Endoluminal administration of verapamil reduces pelvic pressure significantly without any untoward systemic cardiovascular side effects.

Use of the bolus tracking technique for the tomographic evaluation of the uretero-vesicular junction in dogs and assessment of dose records

BACKGROUND

The aim of the work is the application of a bolus tracking technique for tomographic evaluation of the uretero-vesicular junction in dogs. Ten adult dogs (8-14 years) with variable body weight (2,8-32 kg) were enrolled in the prospective study. The patients were placed in sternal recumbency with a 10° elevated pelvis and the visualization of the uretero-vesicular junction was obtained with the bolus tracking technique after intravenous administration of non-ionic contrast medium. In the post-contrast late phase a region of interest was placed within the lumen of the distal ureters and the density values were monitored before starting the helical scan.

RESULTS

The uretero-vesicular junction was clearly visible in 100% of patients with the visualization of the endoluminal ureteral contrast enhancement and bladder washout. At the end of the tomographic study an evaluation of the dose records was performed and compared to human exposures reported in literature for the pelvic region. The effective dose estimated for each patient (37,5-138 mSv) proved to be elevated, when compared to those reported in human patients.

CONCLUSION

The bolus tracking technique could be applied for the visualization of the uretero-vesicular junction in non-pathological patients, placing the region of interest in the distal ureters. The high effective doses recorded in our study support the need of specific thresholds for veterinary patients, pointing out the attention for paediatric patient's exposure also in veterinary imaging.

Red ginseng (Panax ginseng) decreases isoproterenol-induced cardiac injury via antioxidant properties in porcine

Red ginseng (RG, Panax ginseng) has been shown to possess various ginsenosides. These ginsenosides are widely used for treating cardiovascular diseases in Asian communities. The present study was designed to evaluate the cardioprotective potential of RG against isoproterenol (ISO)-induced myocardial infarction (MI), by assessing electrocardiographic, hemodynamic, and biochemical parameters. Male porcines were orally administered with RG (250 and 500 mg/kg) or with vehicle for 9 days, with concurrent intraperitoneal injections of ISO (20 mg/kg) on the 8th and 9th day. RG significantly attenuated ISO-induced cardiac dysfunctions as evidenced by improved ventricular hemodynamic functions and reduced ST segment and QRS complex intervals. Also, RG significantly ameliorated myocardial injury parameters such as antioxidants. Malonaldialdehyde formation was also inhibited by RG. Based on the results, it is concluded that RG possesses significant cardioprotective potential through the inhibition of oxidative stress and may serve as an adjunct in the treatment and prophylaxis of MI.

Ureterovesical junction obstruction causes increment in smooth muscle contractility, and cholinergic and adrenergic activity in distal ureter of rabbits

BACKGROUND/PURPOSE

The controversy in management of primary obstructed megaureter necessitates further elucidation of the underlying pathophysiology. We evaluated smooth muscle contractility, and cholinergic, adrenergic and serotonergic activity of rabbit distal ureters after ureterovesical junction (UVJ) obstruction.

METHODS

Sham (SH) operation, partial obstruction (PO) and complete obstruction (CO) of the right UVJ were performed in rabbits. Three weeks later, distal ureters were isolated; spontaneous contractions (SC), contractile responses to electrical field stimulation (EFS), high KCl, carbachol, phenylephrine and serotonin were recorded.

RESULTS

SC amplitudes increased in CO compared to PO and SH (p<0.001). SC frequency was higher in CO (p<0.05). EFS-induced contraction amplitudes were greater in CO than other groups (p<0.05). High KCl-induced contractions were greater in CO (p<0.001) and PO (p<0.01). Carbachol-induced contractility was enhanced in CO and PO (p<0.05). Contractile response to phenylephrine was greater in CO than other groups (p<0.05). Serotonin induced contractile responses in CO and PO, greater in CO (p<0.05). UVJ obstruction also increased spontaneous contractility in contralateral PO and CO ureters.

CONCLUSIONS

UVJ obstruction increased spontaneous and neurotransmitter-induced contractions in an obstruction grade-dependent manner. Obstruction also altered contractility of the contralateral ureters. Our findings may serve to provide further understanding of the pathophysiology of megaureter.

The effects of local administration of aminophylline on transureteral lithotripsy

Introduction. Urinary stone is a common cause of urinary tract disease. Stone excretion using ureteroscope is effective in inferior ureter. The aim of this study was to investigate the effects of aminophylline on ureteral spasm during ureteroscopy in acute phase of renal colic. Methods. In this double-blind randomized clinical trial, 120 patients with ureteral stones were enrolled and randomized into two groups. The bladder was drained and then received a 150 mL irrigation solution. Irrigation solution was saline and saline plus 10 mL aminophylline at 250 mg dose for control and case groups, respectively. Ureteroscopy and transureteral lithotripsy (TUL) were performed five minutes after irrigation. Results. The mean duration of TUL was 4.2 ± 2.61 min and 8.4 ± 2.9 min for control and case groups, respectively. The successful rate was 95% and 76.1% in case and control groups, respectively. Further extracorporeal shock wave lithotripsy (SWL) was performed in 5% and 30% for patients in case and control groups, respectively. Conclusion. Aminophylline facilitated ureteroscopy and increased the success rate in the treatment of renal colic using TUL. No significant complications from post-TUL were observed. Using aminophylline carries several advantages such as reducing procedure duration, decreasing the need for ureteral and double-J catheter, and reducing stone migration to the kidney and use of SWL.

Gigantic ureteral diverticulum or pelvic cyst?

Ureteral diverticulum is a rare anomaly, and very few reported cases concerning it can be found in literature. We report a 3.5-year-old boy who presented with urinary tract infection, rare voiding, and straining during voiding. Ultrasonography and magnetic resonance imaging showed a cystic pelvic mass. At surgical intervention, however, a massive ureteral cystic structure communicating both with the ureteropelvic and ureterovesical portion of the ureter was observed. Finding the presence of a smooth muscle layer, the pathologist confirmed this to be a true diverticulum. The fact that fenoterol (which was used for the prevention of preterm labor in the boy's mother) significantly decreases frequency and amplitude of upper urinary tract contractions suggests that fenoterol treatment might have influenced the occurrence of this abnormality.

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.

Endoluminal pelvic perfusion with norepinephrine causes only minor systemic effects and diminishes the increase in pelvic pressure caused by perfusion

OBJECTIVE

To evaluate the effect of endoluminal norepinephrine (NE) on transport pressures of the normal upper urinary tract of the pig and on plasma levels of NE in relation to possible systemic effects.

MATERIAL AND METHODS

Six anaesthetized pigs weighing approximately 39 kg were studied. Transparenchymally, two 6-F catheters were introduced into the renal pelvis bilaterally to measure pressure and perfusion. Ultrasonic flow probes recorded renal arterial blood flow, and a transurethral 10-F catheter drained the bladder and monitored diuresis. In all six animals, the bilateral pelvic pressure response was examined at increasing perfusion rates (2, 4, 6, 8, 10 and 15 ml/min) and with increasing doses of NE (0, 5, 50 and 100 microg/ml). Arterial blood samples were analysed for NE, epinephrine and blood glucose. The systemic blood pressure, heart rate and electrocardiogram were registered.

RESULTS

At all the investigated concentrations, endoluminal NE significantly diminished the increase in pelvic pressure caused by pelvic perfusion at all flow rates. At the lowest concentration of NE, no significant increase in the plasma level of NE was observed and the blood pressure did not increase. During perfusion with 50 and 100 microg/ml NE, plasma levels of NE increased significantly from 487+/-398 to 1798+/-910 and 2961+/-2093 pg/ml, respectively. This was accompanied by significant rises in mean systolic blood pressure from a baseline value of 95+/-10 mmHg to 111+/-20 and 118+/-23 mmHg, respectively. Heart rate, renal arterial blood flow and plasma levels of epinephrine and glucose did not change.

CONCLUSIONS

Endoluminal NE diminished the increase in pelvic pressure caused by pelvic perfusion even at concentrations too low to cause significant changes in NE plasma levels or systemic effects. Very high NE concentrations in the perfusion fluid caused increased plasma levels and a modest but significant increase in blood pressure. Administration of endoluminal NE may be useful in upper urinary tract stone treatment and endoscopy.

Endoluminal isoproterenol reduces renal pelvic pressure during semirigid ureterorenoscopy: a porcine model

OBJECTIVE

To investigate the effects on the pressure-flow relation of renal pelvic pressure during semirigid ureterorenoscopy and endoluminal perfusion of isoproterenol (ISO) 0.1 microg/mL, with emphasis on local effects and cardiovascular side-effects, as topically administered ISO effectively and dose-dependently causes relaxation of the upper urinary tract in pigs with no concomitant cardiovascular side-effects.

MATERIALS AND METHODS

In anaesthetized female pigs (60 kg), 16 macroscopically normal upper urinary tract systems were subjected to ureterorenoscopy. Via a subcostal incision a 6-F catheter was placed in the renal pelvis for pressure measurements, and a semirigid ureteroscope (7.8 F) was inserted retrogradely in the renal pelvis, through which the pelvis was perfused. The blood pressure and heart rate were recorded. The increase in renal pelvic pressure was examined with increasing flow rates (0, 4, 8, 12, 16, 25 and 33 mL/min) with saline alone or saline + ISO 0.1 microg/mL. Perfusion was initiated on the left side, with randomization for adding ISO or not. Thereafter perfusion was done on the right side as a control in each pig. The surgeons were unaware of whether ISO was added or not.

RESULTS

The mean (sd) baseline pelvic pressures in the saline and ISO group were 28 (7.1) and 25 (9.8) mmHg, respectively, with no significant difference (P = 0.079). Endoluminal perfusion with ISO significantly inhibited the pelvic pressure increase to perfusion at all perfusion rates. The pressure-flow relation was linear; the maximum relaxation (27%) was obtained at 4 mL/min, from 52 to 38 mmHg during saline alone and ISO 0.1 microg/mL perfusion, respectively. The mean blood pressure did not change significantly (P = 0.330). The mean (sd) heart rate in the saline and ISO group were 109 (4.5) and 97 (2.1) beats/min, respectively (P < 0.001), i.e. a markedly greater rate in the saline than in the ISO group.

CONCLUSION

The pressure-flow relation during semirigid ureterorenoscopy was linear. ISO 0.1 microg/mL in saline significantly reduced the pressure-flow relation during semirigid ureterorenoscopy in this porcine model. ISO might be a potential additive to the irrigation fluid during upper urinary tract endoscopic procedures, minimizing pressure increases due to irrigation and manipulation.

Effects of a non-selective COX inhibitor and selective COX-2 inhibitors on contractility of human and porcine ureters in vitro and in vivo

BACKGROUND AND PURPOSE

Anti-inflammatory drugs are used in the treatment of acute renal colic. The aim of this study was to investigate the effects of selective COX-2 inhibitors and the non-selective COX inhibitor diclofenac on contractility of human and porcine ureters in vitro and in vivo, respectively. COX-1 and COX-2 receptors were identified in human ureter and kidney.

EXPERIMENTAL APPROACH

Human ureter samples were used alongside an in vivo pig model with or without partial ureteral obstruction. COX-1 and COX-2 receptors were located in human ureters by immunohistochemistry.

KEY RESULTS

Diclofenac and valdecoxib significantly decreased the amplitude of electrically-stimulated contractions in human ureters in vitro, the maximal effect (Vmax) being 120 and 14%, respectively. Valdecoxib was more potent in proximal specimens of human ureter (EC50=7.3 x 10(-11) M) than in distal specimens (EC50=7.4 x 10(-10) M), and the Vmax was more marked in distal specimens (22.5%) than in proximal specimens (8.0%) in vitro. In the in vivo pig model, parecoxib, when compared to the effect of its solvent, significantly decreased the maximal amplitude of contractions (Amax) in non-obstructed ureters but not in obstructed ureters. Diclofenac had no effect on spontaneous contractions of porcine ureter in vivo. COX-1 and COX-2 receptors were found to be expressed in proximal and distal human ureter and in tubulus epithelia of the kidney.

CONCLUSIONS AND IMPLICATIONS

Selective COX-2 inhibitors decrease the contractility of non-obstructed, but not obstructed, ureters of the pig in vivo, but have a minimal effect on electrically-induced contractions of human ureters in vitro.

[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.

Endoluminal isoproterenol irrigation decreases renal pelvic pressure during flexible ureterorenoscopy: a clinical randomized, controlled study

OBJECTIVES

Irrigation during ureterorenoscopic procedures causes increased pelvic pressure (PP), which may lead to intrarenal backflow with potential harmful consequences. This study aims to investigate PP response to intraluminal administration of isoproterenol (beta-agonist; ISO) during flexible ureterorenoscopy.

METHODS

Twelve patients admitted for retrograde intrarenal stone surgery (RIRS) were included. Patients were randomized to (1) irrigation with saline (n=6) or (2) irrigation with ISO 0.1 microg/mL (n=6). Irrigation rate was standardized to 8 mL/min. A ureteral catheter was retrogradely placed in the renal pelvis for PP measurements. PP, heart rate (HR), and mean arterial pressure (MAP) were also measured.

RESULTS

Baseline PP was 12.1+/-4mm Hg in the saline group and 10.3+/-4mm Hg in the ISO group (p=0.44). In the saline group, PP increased to a mean 33+/-12 mm Hg during ureterorenoscopy. In the ISO group, PP was a mean 19+/-3mm Hg (p=0.029). During endoscopy, PP peaks as high as 328 mm Hg were noted during saline irrigation. The number of pressure peaks above 50mm Hg was minimized dramatically during ISO irrigation (p=0.035). No systemic side effects to ISO irrigation were observed.

CONCLUSION

For the first time, a randomized, controlled human study demonstrates that pharmacologic modulation of the ureter is possible during upper urinary tract endoscopy. The ability to relax ureteral tone during endoscopy may have clinical advantages.

Renal sympathetic nerve activity modulates afferent renal nerve activity by PGE2-dependent activation of α1- and α2-adrenoceptors on renal sensory nerve fibers

Increasing efferent renal sympathetic nerve activity (ERSNA) increases afferent renal nerve activity (ARNA). To test whether the ERSNA-induced increases in ARNA involved norepinephrine activating α-adrenoceptors on the renal sensory nerves, we examined the effects of renal pelvic administration of the α1- and α2-adrenoceptor antagonists prazosin and rauwolscine on the ARNA responses to reflex increases in ERSNA (placing the rat's tail in 49°C water) and renal pelvic perfusion with norepinephrine in anesthetized rats. Hot tail increased ERSNA and ARNA, 6,930 ± 900 and 4,870 ± 670%·s (area under the curve ARNA vs. time). Renal pelvic perfusion with norepinephrine increased ARNA 1,870 ± 210%·s. Immunohistochemical studies showed that the sympathetic and sensory nerves were closely related in the pelvic wall. Renal pelvic perfusion with prazosin blocked and rauwolscine enhanced the ARNA responses to reflex increases in ERSNA and norepinephrine. Studies in a denervated renal pelvic wall preparation showed that norepinephrine increased substance P release, from 8 ± 1 to 16 ± 1 pg/min, and PGE2 release, from 77 ± 11 to 161 ± 23 pg/min, suggesting a role for PGE2 in the norepinephrine-induced activation of renal sensory nerves. Prazosin and indomethacin reduced and rauwolscine enhanced the norepinephrine-induced increases in substance P and PGE2. PGE2 enhanced the norepinephrine-induced activation of renal sensory nerves by stimulation of EP4 receptors. Interaction between ERSNA and ARNA is modulated by norepinephrine, which increases and decreases the activation of the renal sensory nerves by stimulating α1- and α2-adrenoceptors, respectively, on the renal pelvic sensory nerve fibers. Norepinephrine-induced activation of the sensory nerves is dependent on renal pelvic synthesis/release of PGE2.

Pharmacological effect on pyeloureteric dynamics with a clinical perspective: a review of the literature

We searched to review experimental and clinical trials concerning the capabilities of impacting on the ureteric and pelvic activity by means of pharmacological stimulation. Ureteropyeloscopy may cause high renal pelvic pressure. The normal pressure is in the range of 5-15 mmHg whereas pressure of 410 mmHg has been measured during endoscopy. The threshold pressure for intrarenal reflux is about 35 mmHg. Studies in animals have revealed that high renal pelvic pressures may cause permanent damage to the renal parenchyma. Furthermore, it has been demonstrated that elevated pressures may entail an increased risk of several complications related to endourological procedures including bleeding, perforation and infection. In other words, means by which intrarenal pressure could be lowered during endourological procedures might be beneficial with respect to clinical outcomes. In vitro experiments support the existence of different receptors in the ureter and renal pelvis. The ureteric and pelvic responses to the corresponding neurotransmitters have been determined. It seems that alpha-adrenergic and cholinergic agents are stimulating whereas beta-adrenergic agents inhibit ureteric activity. The effect may depend on the mode of administration. Drugs exerting advantageous effects in the pyeloureter may cause undesirable systemic side effects when administered intravenously. In animal studies, renal pelvic pressure can be significantly lowered by topical administration of beta-adrenergic agonists without systemic side effects. In vivo human studies are necessary to clarify the exact dose-response relationship and the degree of urothelial absorption of a drug before clinical use may be adopted.

Irrigation with isoproterenol diminishes increases in pelvic pressure without side-effects during ureterorenoscopy: a randomized controlled study in a porcine model

OBJECTIVE

Recently, we showed that endoluminally administered isoproterenol (ISO) inhibits muscle function of the pyeloureter in swine. This may be of value in managing increases in pelvic pressure during upper urinary tract endoscopy. The purpose of this study was to examine the effect of endoluminally administered ISO on increases in pelvic pressure and cardiovascular function during flexible ureterorenoscopy.

MATERIAL AND METHODS

The study was performed in anaesthetized female pigs. In terms of endoscopic procedures, the pigs were randomized as follows: Group 1, irrigation with 0.1 microg/ml ISO added to saline (n=12); and Group 2, irrigation with saline (n=10). A 5-Fr catheter was retrogradely placed in the renal pelvis and an 8-Fr catheter in the bladder for pressure measurements. Flexible ureterorenoscopy was performed with constant irrigation at a perfusion rate of 8 ml/min. Pelvic, bladder and blood pressure and heart rate were registered continuously.

RESULTS

Mean baseline pelvic pressure was identical in both groups: 12+/-2.3 mmHg in Group 1 and 14+/-3.6 mmHg in Group 2 (p=0.26). During ureterorenoscopy, mean pelvic pressure increased to 26+/-2.3 mmHg in Group 1 and to 38+/-3.1 mmHg in Group 2. Hence ISO reduced the pressure increase due to ureterorenoscopy by 42% (p<0.001). Pelvic pressure seemed to be independent of bladder pressure, which showed no difference between the two groups (p=0.067). Blood pressure and heart rate showed no significant differences between the two groups: p=0.425 and p=0.166, respectively.

CONCLUSIONS

ISO (0.1 microg/ml) added to irrigation fluid significantly reduces the increase in pelvic pressure during ureterorenoscopy in pigs, without concomitant side-effects.

Effect of smooth muscle relaxant drugs on proximal human ureteric activity in vivo: a pilot study

Drugs are increasingly being used to promote stone passage in renal colic. Diclofenac, nifedipine and tamsulosin cause ureteric smooth muscle relaxation in vitro; however, in clinical trials nifedipine and tamsulosin promote stone passage whereas diclofenac has no apparent benefit. We adapted a ureteric pressure transducer catheter in an attempt to compare the human ureteric response to these drugs in vivo. The catheter was inserted into the contralateral ureter following ureteroscopy for stone disease. Contraction frequency, pressure and velocity measurements were recorded at 24 h. Each patient was randomly allocated to receive oral diclofenac, nifedipine or tamsulosin. Measurements were taken following drug administration. Eighteen patients (mean age 50 years) were recruited. Two patients were excluded intraoperatively and three required early removal of the catheter. Prior to drug administration, the mean number of contractions recorded was 0-4.1/min and the peak contraction pressure ranged from 11 to 35 mmHg. Conduction velocity ranged from 1.5 to 2.6 cm/s. Ureteric peristalsis persisted in all patients despite these drugs. Diclofenac and nifedipine produced inconsistent ureteric pressure responses but had little effect on contraction frequency. Tamsulosin significantly reduced ureteric pressure but had no effect on contraction frequency. There are many limitations associated with the use of ureteric catheters, however, they may provide some useful information when used to record the response to an intervention in the same patient. These preliminary results suggest a reduction in pressure generation may be the essential factor in the promotion of stone passage. More work is required but these drugs may work by preventing the increased, uncoordinated muscular activity seen in renal colic whilst maintaining peristalsis, thereby promoting stone passage.

Local and systemic effects of endoluminal pelvic perfusion of isoproterenol: a dose response investigation in pigs

PURPOSE

Isoproterenol (Sygehus Apotekerne Danmark, Copenhagen, Denmark) is a beta-adrenergic agonist known to cause upper urinary tract relaxation. We studied the local effect on pelvic pressure and the systemic effects of endoluminal perfusion with isoproterenol in a porcine model.

MATERIALS AND METHODS

Pigs weighing 40 kg were studied. Catheters were placed in the renal pelvis for pressure measurement and perfusion, and a catheter was used to drain the bladder. Blood pressure and heart rate were recorded. In 6 pigs in group 1 the pelvic pressure increase was examined at increasing flow rates of 0, 2, 5, 8, 10 and 15 ml per minute with saline containing 0, 10(-3), 10(-2), 10(-1), 1 and 10 microg/ml isoproterenol. Blood values of isoproterenol were analyzed. In 6 pigs in group 2 the pelvis was perfused at a flow rate of 8 ml per minute with saline containing 0, 10(-5), 10(-4), 10(-3), 10(-2), 10(-1), 1 and 10 microg/ml isoproterenol.

RESULTS

In group 1 endoluminal perfusion with isoproterenol inhibited the pelvic pressure increase due to perfusion at all concentrations of isoproterenol. At a perfusion rate of 8 ml per minute the maximal effect (a 78% decrease) was achieved using 0.1 microg/ml isoproterenol without cardiovascular side effects. In group 2 all isoproterenol concentrations caused significant inhibition of the pressure-flow relationship in a dose dependent matter. A 64% decrease in the pressure increase due to saline perfusion was achieved at 0.1 microg/ml isoproterenol without concomitant significant cardiovascular side effects. Isoproterenol was only detected in plasma during perfusion with 1 and 10 microg/ml isoproterenol, which caused significant cardiovascular side effects in the latter case.

CONCLUSIONS

Isoproterenol significantly inhibits the pressure increase due to perfusion in the normal porcine renal pelvis without concomitant cardiovascular side effects. Isoproterenol is a safe drug in this porcine model and, hence, it is potentially useful during endourological procedures.

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.

First Prize: Pharmacologic Manipulation of the Porcine Ureter: Acute Impact of Topical Drugs on Ureteral Diameter and Peristaltic Activity

BACKGROUND AND PURPOSE

Intraluminal application of pharmacologic agents for acute ureteral dilation may facilitate difficult ureteroscopy. We characterized the in-vivo effects of intraluminal application of verapamil and theophylline on ureteral peristalsis and diameter in a porcine model.

MATERIALS AND METHODS

Twenty-four female domestic pigs (35-40 kg) were incorporated into the study. We deployed a giant magneto resistive (GMR) sensor and electromagnetic (EMG) electrodes laparoscopically onto the ureteral surface for simultaneous measurement of the mechanical and electrical signals of ureteral peristalsis, respectively. The ureteral-luminal diameter was measured at three levels by digital retrograde pyelography and standardized to a 10-mm laparoscope. The results were calculated as change in peristalsis and ureteral diameter from baseline during the first hour after drug injection. We tested two smooth-muscle relaxants, verapamil (2 mg/kg) and theophylline (70 mg/kg), with saline and dimethylsulfoxide (DMSO; solvent) as controls. Six pigs were studied for each of the four groups. Hydration, anesthesia, and intra-abdominal pressure were standardized. The serum concentrations of the drugs were measured to determine systemic absorption.

RESULTS

During the first 10 minutes after intraluminal drug injection, theophylline caused a significant decrease in ureteral peristalsis (6.75 waves/10 minutes) compared with the control group (1.00/10 minutes; P = 0.02). This trend persisted for the next hour. However, there were no changes from baseline in ureteral width. Ureteral peristalsis and dilation remained similar after the saline and DMSO injections. Verapamil increased the diameter of the proximal ureter compared with the controls throughout the hour after drug injection. Fifteen minutes after the drug injection, the change in the ureteral diameter with verapamil was 1.38 mm (4.14F), while the control group showed a change of 0.27 mm (P = 0.03). At 1 hour, the width of the proximal ureter in the verapamil group had increased by 1.72 mm (5.16F), while the control group had changed by 0.55 mm (P = 0.03). There were no statistically significant changes in the widths of the mid or distal ureter. No ureteral dilation was observed in the other groups.

CONCLUSIONS

In the porcine model, intraluminal application of pharmacologic agents produced independent effects on ureteral dilation and peristalsis. Theophylline inhibited ureteral peristalsis, and verapamil produced acute proximal-ureteral dilation. The ability to alter ureteral diameter or peristaltic activity acutely may facilitate ureteroscopy.

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.

Regulation of cyclic nucleotides in the urinary tract

Cyclic nucleotide levels are controlled through their synthesis from nucleotide triphosphates by cyclases and their degradation to 5'-monophosphates by phosphodiesterases (PDEs). Components controlling cyclic AMP-induced relaxation in the urinary tract include receptors, inhibitory and stimulatory G-proteins, isoforms of adenylyl cyclase and PDEs. The responsiveness of PDEs to a variety of physiological challenges is related to the presence of multiple families of isoenzymes with specific localization within tissues and within cells. At least 11 families of PDEs encode more than 50 PDE proteins produced in mammalian cells. In the urinary tract, characterization of PDE isoforms has lagged behind other systems and much of the literature was published prior to identification of PDE7, 8, 9, 10, 11. Specific PDE inhibitors regulate smooth muscle function in the bladder, urethra, prostate and ureter. The pharmacological potential of these inhibitors may include treatment of urge incontinence and the low compliance bladder, and treatment of prostate cancer. G-proteins also regulate cyclic AMP production. Changes in specific G- protein isoforms with aging, most prominently Gialpha2, cause decreased relaxation response in the aging bladder. As we have seen here with aging and certainly in other disease processes, levels of the components of adenylyl cyclase/phosphodiesterase/protein kinase can change and thus affect the relaxation response. By exploitation of differences in PDE expression in disease, such as the overexpression of PDEs in cancer, treatment options may present themselves.

PHARMACOLOGICAL CHARACTERIZATION OF β-ADRENOCEPTOR SUBTYPES MEDIATING RELAXATION IN PORCINE ISOLATED URETERAL SMOOTH MUSCLE

PURPOSE

We pharmacologically characterized the functional beta-adrenoceptor subtypes mediating porcine ureteral smooth muscle relaxation.

MATERIALS AND METHODS

The effects of various beta-adrenoceptor agonists and antagonists on KCl induced tonic contractions in isolated porcine ureteral preparations were evaluated using a functional experimental technique.

RESULTS

The rank order of potency for the catecholamines tested was isoprenaline > adrenaline > noradrenaline. All beta2-adrenoceptor agonists tested (salbutamol, procaterol and terbutaline) attenuated the KCl induced contraction. The 2 beta3-adrenoceptor agonists CL-316243 ((R, R)-5-[2-[[2-(3-chlorophenyl)-2-hydroxyethylamino]propyl]-1,3-benzodioxole-2,2-dicarboxylate], Kissei, Nagano, Japan) and CGP-12177A ((+/-)[4-[3[(1,1-dimethylethyl)amino]-2-hydroxypropoxy]-1,3-dihydro-2 H-benzimidazol-2-one hydrochloride], Funakoshi, Tokyo, Japan) also relaxed the ureter. The beta1-adrenoceptor agonist dobutamine had a relaxing effect on the ureter only at high concentrations (over 1 x 10 M). Isoprenaline induced relaxation was antagonized by the beta2-adrenoceptor antagonist ICI-118,551 ((+/-)-1-[(2,3-dihydro-7-methyl-1 H-inden-4-yl)oxy]-3-[(1-methylethyl)amino]-2-butanol hydrochloride, Sigma, St. Louis, Missouri) but not by the beta1-adrenoceptor antagonist CGP 20712A ((+/-)-2-hydroxy-5-[2-[[2-hydroxy-3-[4-[1-methyl-4-(trifluoromethyl)-1 H-imidazol-2-yl]phenoxy]propyl]amino]ethoxy]-benzamide methanesulphonate, Funakoshi). In the presence of 1x 10 M CGP 20712A plus 1 x 10 M ICI-118,551 the beta3-adrenoceptor antagonist SR 58894A (3-(2-allylphenoxy)-1-[(1 S)-1,2,3,4-tetrahydronaphth-1-ylamino]-(2 S)-2-propanol hydrochloride, Kissei) antagonized isoprenaline induced relaxation.

CONCLUSIONS

Our results suggest that porcine ureteral smooth muscle is relaxed by beta2 and beta3-adrenergic stimulation, as in humans.

Ureteric jet in the anaesthetised child

We have already suggested that there is an active bimodal sphincteric mechanism in the human vesicoureteral junction (VUJ). This mechanism is affected by immaturity, hormonal effects and surgical ablation. This study set out to investigate the effects of anaesthesia on this mechanism. A total of 16 children undergoing surgery were recruited. They were well hydrated. The ureteric jets before and after anaesthesia were recorded using the colour and pulse wave Doppler. Of the total, 14 children showed mature (complex pattern) and two showed immature (monophasic pattern) waveforms before surgery. After anaesthesia, all showed the monophasic waveform (p=0.01). Thus, the sphincteric action of VUJ as manifest by the complexity of the ureteric jet was modified by anaesthesia by loss of the complex pattern. This supports the hypothesis that the complex pattern is a neural modulation of the simpler myogenic mechanism that produces the monophasic jet.

Norepinephrine inhibits the pelvic pressure increase in response to flow perfusion

PURPOSE

We evaluated the effects of norepinephrine on transport pressures in the normal upper urinary tract of the pig during increasing perfusion rates.

MATERIALS AND METHODS

Anesthetized Danish landrace Yorkshire pigs weighing 38 to 40 kg were studied. Transparenchymally 2, 6Fr catheters were introduced into the left renal pelvis for pressure measurements and perfusion, respectively. An ultrasonic flow probe was inserted around the left renal artery to record blood flow. A 10Fr catheter was placed transurethrally for bladder drainage and the bladder was maintained empty during the entire study. In the 5 group 1 pigs the pelvic pressure increase was examined at increasing perfusion rates of the renal pelvis (2, 4, 6, 8, 10 and 15 ml per minute) in response to endoluminal administration of increasing concentrations of norepinephrine (0, 5, 50 and 100 microg/ml) in saline. In the 5 group 2 pigs the pressure flow study was also done 4 times per animal using isotonic saline.

RESULTS

Endoluminal norepinephrine had a dose dependent effect on the pressure flow relationship. Perfusion with 5 and 50 microg/ml norepinephrine caused a delayed increase and a decrease in pelvic pressure in response to increasing flow rates, whereas perfusion with 100 microg/ml norepinephrine significantly inhibited and almost eliminated the pressure increase at all perfusion rates compared with saline perfusion. Importantly there were no changes in blood pressure, the heart rate or renal arterial blood flow. In group 2 perfusion with isotonic saline resulted in the same pressure response to increasing flow rates each time.

CONCLUSIONS

Endoluminal administration of norepinephrine caused a dose dependent inhibition on the pressure phases of the pressure flow relationship of the upper urinary tract in pigs. No systemic changes were observed. These observations may provide a useful adjuvant treatment strategy for upper urinary tract stone treatment and endoscopy.

Effects of ketanserin and DOI on spontaneous and 5-HT-evoked peristalsis of the pig ureter in vivo

1. The influence of 5-hydroxytryptamine (5-HT) receptor agonists and antagonists on the ureter motility was investigated in vivo on intact ureters of anaesthetized pigs. Drugs were administered intravenously or topically. 2. 5-HT induced a dose-dependent increase in the frequency of ureter contractions in anaesthetized pigs when given intravenously (0.0001-1 mg kg(-1); ED(50) 0.066 mg kg(-1)) or topically (0.001-1 mg ml(-1); EC(50) 0.043 mg ml(-1)). Significant increases in heart rate and blood pressure were observed when the drug was given intravenously but not topically. 3. The 5-HT(2A) agonist, DOI (1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane) increased the frequency of ureteral contractions in a dose-dependent manner (1-300 microg kg(-1) i.v.). Calculation of ED(50) indicated this compound to be about 1.5 times more potent with an efficacy of 23% compared to 5-HT. 4. The 5-HT(2A/2C) antagonist, ketanserin (0.5 mg kg(-1)) and the 5-HT(2C) antagonist, methysergide (1 mg kg(-1)) antagonized the 5-HT-induced ureter peristalsis when given intravenously. Contraction amplitude, blood pressure and heart rate were not affected by the antagonists. 5. Intravenous (0.0001-1 mg kg(-1)) and topical (0.0001-1 microg ml(-1)) ketanserin significantly decreased the frequency of spontaneous ureteral contractions to about 30% of controls, which could be partly reversed by 5-HT (0.3 mg kg(-1) i.v.). The contraction amplitude, contractions of the contralateral, saline perfused ureter, heart rate and mean arterial blood pressure were not affected. 6. Thus, contractility of porcine ureter is mediated by 5-HT(2) receptors. Their antagonists ketanserin and methysergide seem to be promising drugs for treatment of acute ureteric colic or in preparing the ureter for ureteroscopy.