Propagation of Pacemaker Activity and Peristaltic Contractions in the Mouse Renal Pelvis Rely on Ca2+-activated Cl- Channels and T-Type Ca2+ Channels.

The process of urine removal from the kidney occurs via the renal pelvis (RP). The RP demarcates the beginning of the upper urinary tract and is endowed with smooth muscle cells. Along the RP, organized contraction of smooth muscle cells generates the force required to move urine boluses toward the ureters and bladder. This process is mediated by specialized pacemaker cells that are highly expressed in the proximal RP that generate spontaneous rhythmic electrical activity to drive smooth muscle depolarization. The mechanisms by which peristaltic contractions propagate from the proximal to distal RP are not fully understood. In this study, we utilized a transgenic mouse that expresses the genetically encoded Ca2+ indicator, GCaMP3, under a myosin heavy chain promotor to visualize spreading peristaltic contractions in high spatial detail. Using this approach, we discovered variable effects of L-type Ca2+ channel antagonists on contraction parameters. Inhibition of T-type Ca2+ channels reduced the frequency and propagation distance of contractions. Similarly, antagonizing Ca2+-activated Cl- channels or altering the transmembrane Cl- gradient decreased contractile frequency and significantly inhibited peristaltic propagation. These data suggest that voltage-gated Ca2+ channels are important determinants of contraction initiation and maintain the fidelity of peristalsis as the spreading contraction moves further toward the ureter. Recruitment of Ca2+-activated Cl- channels, likely Anoctamin-1, and T-type Ca2+ channels are required for efficiently conducting the depolarizing current throughout the length of the RP. These mechanisms are necessary for the efficient removal of urine from the kidney.

Mechanosensitive modulation of peristaltic contractions in the mouse renal pelvis.

The renal pelvis develops spontaneous phasic contractions (SPCs) that underlie pyeloureteric peristalsis. Increased urine flow into the renal pelvis mechanically stimulates the contractile machinery within the renal pelvis to facilitate the propagation of peristalsis. Here, the effects of mechanostimulation of the pelvicalyceal junction (PCJ), where SPCs originate from, on the properties of SPCs were investigated. Using the wire myograph, isometric tension changes in tubular preparations of mouse renal pelvis with calyces were circumferentially measured, while mechanostimuli were applied to the PCJ. Immunohistochemistry and intracellular Ca2+ imaging were performed, respectively, to investigate the distribution and functional roles of mechanosensitive TRPV4 channels in the renal pelvis. SPCs periodically originated from PCJ and propagated distally. Mechanostimulation of the PCJ reduced the frequency of SPCs by about 60%, while almost quadrupling their amplitude. Capsaicin (100 nM), an agonist of TRPV1 channels, or calcitonin gene-related peptide (CGRP) (30 nM) also slowed and enlarged SPCs. A prolonged pre-exposure to capsaicin or BIBN4096 (1 µM), a CGRP receptor antagonist, inhibited the mechanostimulation-induced reduction in the SPC frequency, but did not block the increase in SPC amplitude. TRPV4 immunoreactivity was expressed in both atypical (ASMCs) and typical smooth muscle cells (TSMCs). GSK1016790A (100 nM), a TRPV4 agonist, enlarged SPCs independently of TRPV1 or CGRP without increasing the amplitude of spontaneous Ca2+ transients in TSMCs. Thus, mechanostimulation of PCJ appears to activate TRPV1-expressing sensory nerves, releasing CGRP that predominantly reduce the SPC frequency. Activation of TRPV4 may be involved in the mechanosensitive enlargement of SPCs. (247 words).

Isolating and Imaging Live, Intact Pacemaker Regions of Mouse Renal Pelvis by Vibratome Sectioning.

The renal pelvis (RP) is a funnel-shaped, smooth muscle structure that facilitates normal urine transport from the kidney to the ureter by regular, propulsive contractions. Regular RP contractions rely on pacemaker activity, which originates from the most proximal region of the RP at the pelvis-kidney junction (PKJ). Due to the difficulty in accessing and preserving intact preparations of the PKJ, most investigations on RP pacemaking have focused on single-cell electrophysiology and Ca2+ imaging experiments. Although important revelations on RP pacemaking have emerged from such work, these experiments have several intrinsic limitations, including the inability to accurately determine cellular identity in mixed suspensions and the lack of in situ imaging of RP pacemaker activity. These factors have resulted in a limited understanding of the mechanisms that underlie normal rhythmic RP contractions. In this paper, a protocol is described to prepare intact segments of mouse PKJ using a vibratome sectioning technique. By combining this approach with mice expressing cell-specific reporters and genetically encoded Ca2+ indicators, investigators may be able to more accurately study the specific cell types and mechanisms responsible for peristaltic RP contractions that are vital for normal urine transport.

An Interesting Relationship Between Maternal Adipose Tissue Thickness and Maternal Pelvicalyceal System Dilatation.

PURPOSE: To evaluate whether maternal body mass index (BMI), visceral adipose tissue (VAT) thickness, and sub-cutaneous adipose tissue (SAT) thickness have effects on maternal pelvicalyceal system dilatation, which develops during pregnancy. MATERIALS AND METHODS: Between April 2018 and November 2018, a total of 120 pregnant women aged between 18-35 years in their third trimester were included in this prospective observational study. For each pregnant wom-an, SAT and VAT thicknesses were measured and renal sonography was performed by the same radiologist and obstetric ultrasound was performed by the same obstetrician. Nine patients were excluded from the study because their maximal caliceal diameters were less than 5 mm. Ultimately, 111 patients were divided into three groups according to the maximal calyceal diameter (MCD). RESULTS: Asymptomatic hydronephrosis was diagnosed in 108/111 (97.3%) of the patients. There were 53 patients in group 1 (MCD of 5-10 mm), 39 patients in group 2 (MCD of 10-15 mm), and 19 patients in group 3 (MCD of >15 mm). There were statistically significant differences in terms of maternal SAT and VAT thickness between the groups (P = .001). There were also statistically significant differences between the groups for the estimated fetal weight and birth weight (P = .024, P = .003, respectively). In the correlation analysis, there was a negative correlation between maternal SAT thickness, VAT thicknesses, BMI, and maximal calyceal diameter (P = .001). CONCLUSION: In this study, relationships between maternal BMI, VAS thickness, SAT thickness, the estimated fetal weight, birth weight, and renal pelvicalyceal dilatation have been shown. Increasing maternal adipose tissue may have a protective effect of mechanical pressure of growing uterus on the ureters.

A Novel Technique to Intelligently Monitor and Control Renal Pelvic Pressure during Minimally Invasive Percutaneous Nephrolithotomy.

OBJECTIVE: To introduce a novel technique for intelligently monitoring and controlling renal pelvic pressure (RPP) in minimally invasive percutaneous nephrolithotomy (MPCNL) and to investigate its reliability and stability. MATERIALS AND METHODS: A total of 63 kidney stone patients (41 males and 22 females) were enrolled in the study. The average stone size was 3.7 ± 1.1 cm. The average age was 41.6 ± 15.6 years old. All patients underwent MPCNL under combined spinal and epidural anesthesia in prone position. A ureteral catheter connected to an invasive blood pressure monitor was retrogradely placed to measure renal pelvic outlet pressure. The MPCNL was performed with the aid of the patented device, including an irrigation and suctioning platform and a pressure-measuring suctioning sheath. On the platform, the RPP control value was set at -5 mm Hg, and the RPP warning value was set at 20 mm Hg. RPP was measured during the irrigation and suctioning period (ISP), and therapeutic period (TP) when the infusion flow was set at 300, 400, and 500 mL/min, respectively, for 5 min. RESULTS: Sixty-three patients successfully underwent the procedure without serious complications. The mean operative time was 67 min (range 31-127 min). Three patients had residual stones >2 mm in size. No statistical significance was observed between the renal pelvic outlet pressure, platform RPP values, and RPP control values for the 300, 400, and 500 mL/min groups during the ISP and TP (p > 0.05). CONCLUSION: The patented devices including the platform and the sheath can reliably and stably monitor and control RPP in real time and within a safe range during MPCNL.

Pacemaker Mechanisms Driving Pyeloureteric Peristalsis: Modulatory Role of Interstitial Cells.

The peristaltic pressure waves in the renal pelvis that propel urine expressed by the kidney into the ureter towards the bladder have long been considered to be 'myogenic', being little affected by blockers of nerve conduction or autonomic neurotransmission, but sustained by the intrinsic release of prostaglandins and sensory neurotransmitters. In uni-papilla mammals, the funnel-shaped renal pelvis consists of a lumen-forming urothelium and a stromal layer enveloped by a plexus of 'typical' smooth muscle cells (TSMCs), in multi-papillae kidneys a number of minor and major calyces fuse into a large renal pelvis. Electron microscopic, electrophysiological and Ca2+ imaging studies have established that the pacemaker cells driving pyeloureteric peristalsis are likely to be morphologically distinct 'atypical' smooth muscle cells (ASMCs) that fire Ca2+ transients and spontaneous transient depolarizations (STDs) which trigger propagating nifedipine-sensitive action potentials and Ca2+ waves in the TSMC layer. In uni-calyceal kidneys, ASMCs predominately locate on the serosal surface of the proximal renal pelvis while in multi-papillae kidneys they locate within the sub-urothelial space. 'Fibroblast-like' interstitial cells (ICs) located in the sub-urothelial space or adventitia are a mixed population of cells, having regional and species-dependent expression of various Cl-, K+, Ca2+ and cationic channels. ICs display asynchronous Ca2+ transients that periodically synchronize into bursts that accelerate ASMC Ca2+ transient firing. This review presents current knowledge of the architecture of the proximal renal pelvis, the role Ca2+ plays in renal pelvis peristalsis and the mechanisms by which ICs may sustain/accelerate ASMC pacemaking.

Protein Kinase 2ß Is Expressed in Neural Crest-Derived Urinary Pacemaker Cells and Required for Pyeloureteric Contraction.

Nonobstructive hydronephrosis, defined as dilatation of the renal pelvis with or without dilatation of the ureter, is the most common antenatal abnormality detected by fetal ultrasound. Yet, the etiology of nonobstructive hydronephrosis is poorly defined. We previously demonstrated that defective development of urinary tract pacemaker cells (utPMCs) expressing hyperpolarization-activated cyclic nucleotide-gated channel 3 (HCN3) and the stem cell marker cKIT causes abnormal ureteric peristalsis and nonobstructive hydronephrosis. However, further investigation of utPMC development and function is limited by lack of knowledge regarding the embryonic derivation, development, and molecular apparatus of these cells. Here, we used lineage tracing in mice to identify cells that give rise to utPMCs. Neural crest cells (NCCs) indelibly labeled with tdTomato expressed HCN3 and cKIT. Furthermore, purified HCN3+ and cKIT+ utPMCs were enriched in Sox10 and Tfap-2α, markers of NCCs. Sequencing of purified RNA from HCN3+ cells revealed enrichment of a small subset of RNAs, including RNA encoding protein kinase 2ß (PTK2ß), a Ca2+-dependent tyrosine kinase that regulates ion channel activity in neurons. Immunofluorescence analysis in situ revealed PTK2ß expression in NCCs as early as embryonic day 12.5 and in HCN3+ and cKIT+ utPMCs as early as embryonic day 15.5, with sustained expression in HCN3+ utPMCs until postnatal week 8. Pharmacologic inhibition of PTK2ß in murine pyeloureteral tissue explants inhibited contraction frequency. Together, these results demonstrate that utPMCs are derived from NCCs, identify new markers of utPMCs, and demonstrate a functional contribution of PTK2ß to utPMC function.

Hydrodynamic Renal Pelvis Injection for Non-viral Expression of Proteins in the Kidney.

Hydrodynamic injection creates a local, high-pressure environment to transfect various tissues with plasmid DNA and other substances. Hydrodynamic tail vein injection, for example, is a well-established method by which the liver can be transfected. This manuscript describes an application of hydrodynamic principles by injection of the mouse kidney directly with plasmid DNA for kidney-specific gene expression. Mice are anesthetized and the kidney is exposed by a flank incision followed by a fast injection of a plasmid DNA-containing solution directly into the renal pelvis. The needle is kept in place for ten seconds and the incision site is sutured. The following day, live animal imaging, Western blot, or immunohistochemistry may be used to assay gene expression, or other assays suited to the transgene of choice are used for detection of the protein of interest. Published methods to prolong gene expression include transposon-mediated transgene integration and cyclophosphamide treatment to inhibit the immune response to the transgene.

Maternal Physiologic Renal Pelvis Dilatation in Pregnancy: Sonographic Reference Data.

OBJECTIVES: The purpose of this study was to produce sonographic reference data for maternal renal pelvis dilatation in asymptomatic pregnant women. METHODS: A prospective cross-sectional study was undertaken on pregnant women presenting for outpatient obstetric imaging. For each side, the renal length and axial anteroposterior diameter of the renal pelvis were measured. Maternal demographics, gravidity and parity, number of fetuses, and estimated fetal weight (when available) were recorded. RESULTS: A total of 700 women enrolled, with 191 excluded. The 509 women analyzed included 465 singleton and 44 twin pregnancies. A total of 815 sonographic investigations were performed: 716 in singleton pregnancies and 99 in twin pregnancies. The gestational age range was 10 to 40 weeks. Charts depicting the anteroposterior renal pelvis diameter versus gestational age were constructed to determine normative sonographic reference data for maternal renal pelvis dilatation in singleton pregnancies. Although the mean renal pelvis diameter increased as pregnancy progressed, measurements of greater than 10 mm remained relatively uncommon, being identified in 9.7% of right and 2.1% of left kidneys in the third trimester. Only 4.1% of right and 0.4% of left third-trimester measurements exceeded 15 mm. Right renal pelvis measurements on average were greater than the left by 1.54 mm (95% confidence interval [CI], 1.20 to 1.87 mm). Twins had significantly larger renal pelvis measurements than singletons on average, measuring 2.11 mm (95% CI, 1.50 to 2.72 mm) larger on the right and 1.69 mm (95% CI, 0.73 to 2.65) on the left. CONCLUSIONS: We present sonographic reference data for asymptomatic pregnancy-related renal pelvis dilatation in singleton pregnancies from a large cohort of women.

Autonomic and sensory nerve modulation of peristalsis in the upper urinary tract.

The primary function of the upper urinary tract is to propel urine and various water-soluble toxic compounds from the kidneys to the bladder for storage and evacuation to maintain body ionic balance and contribute to the regulation of blood volume and pressure. The mechanism by which the upper urinary tract propels urine has long been considered to be myogenic in origin as peristaltic contractions in vivo and in vitro (pyeloureteric peristalsis) propagate in a manner little affected by drugs that block nerve conduction or the sympathetic and parasympathetic transmission. However, it is now well established that the release of intrinsic prostaglandins and neuropeptides from primary sensory nerves (PSNs) helps to maintain pyeloureteric peristalsis. Electrical field stimulation of PSNs evokes species-specific positive inotropic and chronotropic effects that have been attributed to release of excitatory tachykinins superimposed on negative inotropic and chronotropic effects associated with the release of calcitonin gene related peptide (CGRP), a rise in cellular cyclic-adenosine monophosphate (cAMP) and a protein kinase A-dependent activation of glibenclamide-sensitive ATP-dependent K+ (KATP) channels. This review summarises the existing evidence of the nervous control of the upper urinary tract and recent evidence suggesting that the autonomic innervation may indirectly modulate pyeloureteric peristalsis via the activation of PSN nicotinic receptors and via the modulation of KV7 channels located on interstitial cells within the renal pelvis wall.

Effects of renal denervation on renal pelvic contractions and connexin expression in rats.

AIMS: The renal pelvis shows spontaneous rhythmic contractile activity. We assessed to what extent this activity depends on renal innervation and studied the role of connexins in pelvic contractions. METHODS: Rats underwent unilateral renal denervation or renal transplantation. Renal pelvic pressure and diuresis were measured in vivo. Spontaneous and agonist-induced contractions of isolated renal pelves were investigated by wire myography. Rat and human renal pelvic connexin mRNA abundances and connexin localization were studied by real-time PCR and immunofluorescence respectively. RESULTS: Renal denervation or transplantation increased renal pelvic pressure in vivo by about 60 and 150%, respectively, but did not significantly affect pelvic contraction frequency. Under in vitro conditions, isolated pelvic preparations from innervated or denervated kidneys showed spontaneous contractions. Pelves from denervated kidneys showed about 50% higher contraction frequencies than pelves from innervated kidneys, whereas contraction force was similar in pelves from denervated and innervated kidneys. There was no denervation-induced supersensitivity to noradrenaline or endothelin-1. Renal denervation did not increase pelvic connexin37, 40, 43 or 45 mRNA abundances. Gap junction blockade had no effect on spontaneous pelvic contractile activity. CONCLUSIONS: The denervation-induced effect on pelvic pressure may be the consequence of the enhanced diuresis. The mechanisms underlying the denervation-induced effects on pelvic contraction frequency remain unknown. Our data rule out a major role for two important candidates, by showing that renal denervation neither induced supersensitivity to contractile agonists nor increased connexin mRNA abundance in the pelvic wall.

Effects of Alpha-Blockade on Ureteral Peristalsis and Intrapelvic Pressure in an In Vivo Stented Porcine Model.

INTRODUCTION: Clinical studies have shown beneficial role of oral alpha-blockers for ureteral stent-related morbidity. However, the in vivo effects of oral alpha-blockers on a stented ureter are unclear. We evaluated the effects of alpha-blockade on ureteral dynamics in a stented porcine ureter. METHODS: Twenty-seven female pigs were used in this study. Fourteen pigs received oral alpha-blocker medication (silodosin, 8 mg daily), and 13 pigs received no medication. Under cystoscopic guidance, a 5F ureteral catheter was positioned in the renal pelvis and attached to a pressure monitor. A Foley catheter was placed in the bladder along with a bladder pressure transducer. A lumbotomy was performed, and the ureter was identified. A magnetic sensor was placed on the extraluminal surface of the ureter to monitor ureteral peristalsis. We measured renal pelvic and bladder pressures, urine output, and ureteral peristalsis every hour for 10 minutes for a total of 5 hours. The pigs were then euthanized. RESULTS: The mean weight was 42.5 kg in the drug group and 45.9 kg in the nondrug group (p = 0.008). Mean hourly urine output was 140 mL in the drug group and 144 mL in the nondrug group (p = 0.76). Mean baseline renal pressure was 13.2 and 13.8 mm Hg (p = 0.69) in the drug and nondrug groups, respectively. Mean peristaltic renal pelvic pressure was 19.1 mm Hg in the drug group and 19.2 mm Hg in the nondrug group (p = 0.97). Mean number of peristalsis was 11/10 and 14/10 minutes (p = 0.03) in the drug and nondrug groups, respectively. CONCLUSIONS: Alpha-blockade in an in vivo stented porcine ureter resulted in no significant effect on renal pelvic pressure but a significant decrease in the number of ureteral peristalsis. Further investigation of the effects of alpha-blocker on ureteral dynamics is required to better understand its effects on stent-related symptoms.

Electrical propagation in the renal pelvis, ureter and bladder.

Under normal conditions, following the passage of urine from the collecting duct, the urine is stored briefly in the renal pelvis before being transported through the ureter to the bladder where the urine is stored for a longer time (hours) before being voided through the urethra. The transport of urine from the renal pelvis to the bladder occurs spontaneously due to contractions of the muscles in the wall of the pelvis and ureter. Spontaneous contractions also occur in the detrusor muscle and are responsible for maintaining the bladder shape during the filling phase. These muscle contractions occur as result of electrical impulses, which are generated and propagated through different parts of the urinary tract. The renal pelvis and the ureter differ from the bladder in relation to the origin, characteristics and propagation of these electrical impulses. In the ureter, the electrical impulses originate mainly at the proximal region of the renal pelvis and are transmitted antegradely down the length of the ureter. The electrical impulses in the bladder, on the other hand, originate at any location in the bladder wall and can be transmitted in different directions with the axial direction being the prominent one. In this manuscript, an overview of the current state of research on the origin and propagation characteristics of these electrical impulses in the normal and pathological conditions is provided.

The Whitaker test.

PURPOSE: The Whitaker test was conceived and developed by Roger H. Whitaker (May 25, 1939) while he was a resident at Cambridge University in the late 1960s and early 1970s. The test combines a urodynamic study with antegrade pyelography to measure the pressure differential between the renal pelvis and the bladder. The test can differentiate between patients with residual or recurrent obstruction and those with dilatation secondary to permanent changes in the musculature. MATERIALS AND METHODS: We present the history of the Whitaker test and its place in modern practice. RESULTS: It is useful in evaluating patients with questionable ureteropelvic or ureterovesical junction obstruction and primary defects in the ureteral musculature. It can also be used to determine when percutaneous nephrostomy tubes can be safely discontinued in postoperative patients. CONCLUSION: The merit of the Whitaker test in comparison to other less invasive tests, specifically diuretic renography, is the subject of much debate. However, such debate erroneously presupposes that the tests are directly comparable, which they are not. The correct use for the Whitaker test is to assesses potential upper tract obstruction in equivocal cases and should only be utilized when equivocal results are obtained by other less invasive tests, obstruction is suspected in a poorly functioning kidney, a negative renogram with colic, intermittent obstruction, and percutaneous access already exists and the cause of dilatation needs investigating.

High-resolution mechanical imaging of the kidney.

The objective of this study was to test the feasibility and reproducibility of in vivo high-resolution mechanical imaging of the asymptomatic human kidney. Hereby nine volunteers were examined at three different physiological states of urinary bladder filling (a normal state, urinary urgency, and immediately after urinary relief). Mechanical imaging was performed of the in vivo kidney using three-dimensional multifrequency magnetic resonance elastography combined with multifrequency dual elastovisco inversion. Other than in classical elastography, where the storage and loss shear moduli are evaluated, we analyzed the magnitude |G(⁎)| and the phase angle φ of the complex shear modulus reconstructed by simultaneous inversion of full wave field data corresponding to 7 harmonic drive frequencies from 30 to 60Hz and a resolution of 2.5mm cubic voxel size. Mechanical parameter maps were derived with a spatial resolution superior to that in previous work. The group-averaged values of |G(⁎)| were 2.67±0.52kPa in the renal medulla, 1.64±0.17kPa in the cortex, and 1.17±0.21kPa in the hilus. The phase angle φ (in radians) was 0.89±0.12 in the medulla, 0.83±0.09 in the cortex, and 0.72±0.06 in the hilus. All regional differences were significant (P<0.001), while no significant variation was found in relation to different stages of bladder filling. In summary our study provides first high-resolution maps of viscoelastic parameters of the three anatomical regions of the kidney. |G(⁎)| and φ provide novel information on the viscoelastic properties of the kidney, which is potentially useful for the detection of renal lesions or fibrosis.

Nicotinic receptor activation on primary sensory afferents modulates autorhythmicity in the mouse renal pelvis.

BACKGROUND AND PURPOSE: The modulation of the spontaneous electrical and Ca(2+) signals underlying pyeloureteric peristalsis upon nicotinic receptor activation located on primary sensory afferents (PSAs) was investigated in the mouse renal pelvis. EXPERIMENTAL APPROACH: Contractile activity was followed using video microscopy, electrical and Ca(2+) signals in typical and atypical smooth muscle cells (TSMCs and ASMCs) within the renal pelvis were recorded separately using intracellular microelectrodes and Fluo-4 Ca(2+) imaging. KEY RESULTS: Nicotine and carbachol (CCh; 1-100 µM) transiently reduced the frequency and increased the amplitude of spontaneous phasic contractions in a manner unaffected by muscarininc antagonists, 4-DAMP (1,1-dimethyl-4-diphenylacetoxypiperidinium iodide) and pirenzipine (10 nM) or L-NAME (L-Nω-nitroarginine methyl ester; 200 µM), inhibitor of NO synthesis, but blocked by the nicotinic antagonist, hexamethonium or capsaicin, depletor of PSA neuropeptides. These negative chronotropic and delayed positive inotropic effects of CCh on TSMC contractions, action potentials and Ca(2+) transients were inhibited by glibenclamide (Glib; 1 µM), blocker of ATP-dependent K (KATP) channels. Nicotinic receptor-evoked inhibition of the spontaneous Ca(2+) transients in ASMCs was prevented by capsaicin but not Glib. In contrast, the negative inotropic and chronotropic effects of the non-selective COX inhibitor indomethacin were not prevented by Glib. CONCLUSIONS AND IMPLICATIONS: The negative chronotropic effect of nicotinic receptor activation results from the release of calcitonin gene-related peptide (CGRP) from PSAs, which suppresses Ca(2+) signalling in ASMCs. PSA-released CGRP also evokes a transient hyperpolarization in TSMCs upon the opening of KATP channels, which reduces contraction propagation but promotes the recruitment of TSMC Ca(2+) channels that underlie the delayed positive inotropic effects of CCh.

Endoluminal pharmacologic stimulation of the upper urinary tract.

The experiments performed in this PhD thesis were conducted at the Institute of Experimental Surgery, Skejby Hospital, Aarhus, Denmark and at the Laboratory of Animal Science, Odense University Hospital, Denmark. The thesis is based on 3 peer review articles published in international journals and a review. Diagnostic or therapeutic endoscopic upper urinary tract procedures are usually characterised as minimal invasive procedures and associated with a low complication rate. Most often fever or pain are seen and sometimes septicaemia. However, mucosa lesion or even ureteric ruptures are known complications. Research has suggested that high renal pelvic pressures generated during these procedures, might contribute to per-/postoperative complications seen, and even possible renal parenchymal damage. Nevertheless, local administration (endoluminal) of a relaxant drug has not previously been tried in order to lower renal pelvic pressure. The purposes of this thesis were to examine the effect of local administration (endoluminal) of the nonspecific ß-adrenergic agonist ISOproterenol (ISO) on: 1) The normal pressure flow relation in porcine ureter, 2) The effect of endoluminal ISO perfusion during flexible ureterorenoscopy, 3) The pressure flow relation during semirigid ureterorenoscopy and 4) The cardiovascular system. Among other receptor-types ß-adrenergic receptor are located in the upper urinary tract and the activation thereof mediates smooth muscle relaxation. We have shown - in an animal experimental model - that ISO added to the irrigation fluid had significant impact on the renal pelvic pressures generated during upper urinary tract endoscopy. ISO significantly and dose dependently reduced the normal pressure flow relations by approximately 80% without concomitant cardiovascular side effects or measurable plasma levels of ISO. During flexible ureterorenoscopy 0.1 µg/ml ISO added to the irrigation fluid significantly reduced renal pelvic pressure during perfusion compared to saline perfusion alone. Pressures obtained during ISO perfusion were kept below the critical pressure for intrarenal reflux. The pressure flow relation during semirigid ureterorenoscopy was linear and ISO reduced pelvic pressure significantly, but not below the critical level for intrarenal reflux. In conclusion, ISO 0.1 µg/ml added to the irrigation fluid during endoscopic procedures was safe in this porcine model. Alongside this thesis, we have demonstrated the relaxing potency of 0.1 µg/ml ISO added to the irrigation fluid in a human trial and found it safe. Future research in this area, especially randomized clinical trials, regarding the relaxing potency, complication rates, pain episodes etc. should be evaluated. The addition of a relaxant drug to the irrigation fluid may prove to favour therapeutic or diagnostic endoscopic procedures in the upper urinary tract in the future.

Renal sensory and sympathetic nerves reinnervate the kidney in a similar time-dependent fashion after renal denervation in rats.

Efferent renal sympathetic nerves reinnervate the kidney after renal denervation in animals and humans. Therefore, the long-term reduction in arterial pressure following renal denervation in drug-resistant hypertensive patients has been attributed to lack of afferent renal sensory reinnervation. However, afferent sensory reinnervation of any organ, including the kidney, is an understudied question. Therefore, we analyzed the time course of sympathetic and sensory reinnervation at multiple time points (1, 4, and 5 days and 1, 2, 3, 4, 6, 9, and 12 wk) after renal denervation in normal Sprague-Dawley rats. Sympathetic and sensory innervation in the innervated and contralateral denervated kidney was determined as optical density (ImageJ) of the sympathetic and sensory nerves identified by immunohistochemistry using antibodies against markers for sympathetic nerves [neuropeptide Y (NPY) and tyrosine hydroxylase (TH)] and sensory nerves [substance P and calcitonin gene-related peptide (CGRP)]. In denervated kidneys, the optical density of NPY-immunoreactive (ir) fibers in the renal cortex and substance P-ir fibers in the pelvic wall was 6, 39, and 100% and 8, 47, and 100%, respectively, of that in the contralateral innervated kidney at 4 days, 4 wk, and 12 wk after denervation. Linear regression analysis of the optical density of the ratio of the denervated/innervated kidney versus time yielded similar intercept and slope values for NPY-ir, TH-ir, substance P-ir, and CGRP-ir fibers (all R(2) > 0.76). In conclusion, in normotensive rats, reinnervation of the renal sensory nerves occurs over the same time course as reinnervation of the renal sympathetic nerves, both being complete at 9 to 12 wk following renal denervation.

Is the pelviureteric junction an anatomical entity?

OBJECTIVE: The concept of the pelviureteric junction has existed for more than a century and yet there is no clear anatomical definition of this junction. This systematic review addresses the question of whether the human pelviureteric junction is a discrete anatomical entity. METHODS: A systematic literature review was undertaken to investigate the normal gross and microscopic anatomy of the pelviureteric junction using the electronic databases MEDLINE, PubMed, Cochrane Library and Google Scholar. RESULTS: In most individuals there is a gradual transition between the renal pelvis and ureter with no external features indicating the presence of a discrete pelviureteric 'junction'. Internally, however, luminal mucosal folds are prominent in this region. There is no consensus on the arrangement of muscle fibers at the pelviureteric junction (which may be age-dependent) although some studies suggest a focal thickening in the muscle wall consistent with physiological observations suggesting a high pressure zone capable of regulating urine flow. Studies of innervation have shown no evidence of specialization at this site. CONCLUSIONS: There is some evidence that a pelviureteric region can be delineated anatomically and physiologically. However, although it may be a useful clinical concept, there is no sound anatomical basis for an actual pelviureteric junction.

Use and limitations of three TRPV-1 receptor antagonists on smooth muscles of animals and man: a vote for BCTC.

Specificity of the effect is a crucial factor in using antagonists for detecting the physiological/pathophysiological roles of receptors. Here we examined the capsaicin receptor antagonist effects of three commercially-available substances, capsazepine, iodo-resiniferatoxin (I-RTX) and BCTC, on isolated smooth muscle preparations, including the human intestine. Care was taken to observe possible non-specific effects, to find out safe and effective concentrations. Capsazepine appeared to have a low margin of safety. I-RTX (up to 1µM) specifically inhibited capsaicin-induced contractions in the guinea-pig ileum and urinary bladder. I-RTX showed agonist activity on the rat urinary bladder. BCTC (1µM) abolished the contractile effects of capsaicin (1 or 2µM) on all preparations tested (guinea-pig ileum, bladder, trachea, as well as rat and mouse bladder), and on the guinea-pig renal pelvis, where it failed to influence capsaicin-sensitive, sensory neuron-mediated positive inotropy in response to field stimulation. On human intestinal preparations BCTC prevented the relaxant effect of capsaicin. It is concluded that of the three antagonists tested BCTC seems the safest one for inhibiting TRPV-1 receptors. The effect of capsazepine may be complicated by non-specific inhibition of smooth muscle contractility and that of I-RTX by agonist activity. The "local efferent" function of capsaicin-sensitive sensory neurons is not influenced by BCTC, as shown by the results obtained in the renal pelvis. In conclusion, of the TRPV-1 receptor antagonists studied, BCTC (1µM) seems the most reliable in isolated organ experiments. This substance is also effective in the human intestine.