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.

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.

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.

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.

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.

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).

Dietary sodium modulates the interaction between efferent and afferent renal nerve activity by altering activation of α2-adrenoceptors on renal sensory nerves.

Activation of efferent renal sympathetic nerve activity (ERSNA) increases afferent renal nerve activity (ARNA), which then reflexively decreases ERSNA via activation of the renorenal reflexes to maintain low ERSNA. The ERSNA-ARNA interaction is mediated by norepinephrine (NE) that increases and decreases ARNA by activation of renal α(1)-and α(2)-adrenoceptors (AR), respectively. The ERSNA-induced increases in ARNA are suppressed during a low-sodium (2,470 ± 770% s) and enhanced during a high-sodium diet (5,670 ± 1,260% s). We examined the role of α(2)-AR in modulating the responsiveness of renal sensory nerves during low- and high-sodium diets. Immunohistochemical analysis suggested the presence of α(2A)-AR and α(2C)-AR subtypes on renal sensory nerves. During the low-sodium diet, renal pelvic administration of the α(2)-AR antagonist rauwolscine or the AT1 receptor antagonist losartan alone failed to alter the ARNA responses to reflex increases in ERSNA. Likewise, renal pelvic release of substance P produced by 250 pM NE (from 8.0 ± 1.3 to 8.5 ± 1.6 pg/min) was not affected by rauwolscine or losartan alone. However, rauwolscine+losartan enhanced the ARNA responses to reflex increases in ERSNA (4,680 ± 1,240%·s), and renal pelvic release of substance P by 250 pM NE, from 8.3 ± 0.6 to 14.2 ± 0.8 pg/min. During a high-sodium diet, rauwolscine had no effect on the ARNA response to reflex increases in ERSNA or renal pelvic release of substance P produced by NE. Losartan was not examined because of low endogenous ANG II levels in renal pelvic tissue during a high-sodium diet. Increased activation of α(2)-AR contributes to the reduced interaction between ERSNA and ARNA during low-sodium intake, whereas no/minimal activation of α(2)-AR contributes to the enhanced ERSNA-ARNA interaction under conditions of high sodium intake.

Interstitial cells of Cajal in the urinary tract.

The study of novel interstitial cells in the tissues of the urinary tract has defined advances in the field in the last decade. These intriguing cells belong to the same family as the better known interstitial cells of Cajal (ICC) of the gastrointestinal tract, and their discovery has been interpreted to suggest that pacemaker cells may be present in the urinary tract, driving the spontaneous or myogenic activity of the neighboring smooth muscle. This scenario may be true for the urethra where ICC have been described as "loose pacemakers" providing multiple, random inputs to modulate urethral smooth muscle activity. However, there is a paucity of direct evidence available to support this hypothesis in the bladder (where the smooth muscle cells are spontaneously active) or the renal pelvis (where atypical smooth muscle cells are the pacemakers), and it now seems more likely that urinary tract ICC act as modulators of smooth muscle activity.Interestingly, the literature suggests that the role of urinary tract ICC may be more apparent in pathophysiological conditions such as the overactive bladder. Several reports have indicated that the numbers of ICC present in overactive bladder tissues are greater than those from normal tissues; moreover, the contractility of tissues from overactive bladders in vitro appears to be more sensitive to the Kit antagonist, glivec, than those from normal bladder. Future research on urinary tract ICC in the short to medium term is likely to be dynamic and exciting and will lead to increasing our understanding of the roles of these cells in both normal and dysfunctional bladder.

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.

The pelvis-kidney junction contains HCN3, a hyperpolarization-activated cation channel that triggers ureter peristalsis.

Peristaltic waves of the ureteric smooth muscles move urine down from the kidney, a process that is commonly defective in congenital diseases. To study the mechanisms that control the initiation and direction of contractions, we used video microscopy and optical mapping techniques and found that electrical and contractile waves began in a region where the renal pelvis joined the connective tissue core of the kidney. Separation of this pelvis-kidney junction from more distal urinary tract segments prevented downstream peristalsis, indicating that it housed the trigger for peristalsis. Moreover, cells in the pelvis-kidney junction were found to express isoform 3 of the hyperpolarization-activated cation on channel family known to be required for initiating electrical activity in the brain and heart. Immunocytochemical and real-time PCR analyses found that hyperpolarization-activated cation-3 is expressed at the pelvis-kidney junction where electrical excitation and contractile waves originate. Inhibition of this channel caused a loss of electrical activity at the pelvis-kidney junction and randomized the origin of electrical activity in the urinary tract, thus markedly perturbing contractions. Collectively, our study demonstrates that hyperpolarization-activated cation-3 channels play a fundamental role in coordinating proximal-to-distal peristalsis of the upper urinary tract. This provides insight into the genetic causes of common inherited urinary tract disorders such as reflux and obstruction.

Role of hyperpolarization-activated cation channels in pyeloureteric peristalsis.

Although it has been recognized for more than 140 years that the pacemaker driving pyeloureteric peristalsis resides within the kidney, the cellular mechanisms underlying this autorhythmicity have been little investigated. The demonstration by Hurtado et al. of a role of hyperpolarization-activated cation channels in the maintenance of coordinated propagating contractions in the mouse renal pelvis raises a number of intriguing possibilities in addition to the provided correlation with 'pacemaker' function as in the heart and neurons.

Spontaneous electrical and Ca2+ signals in the mouse renal pelvis that drive pyeloureteric peristalsis.

1. Peristalsis in the smooth muscle cell (SMC) wall of the pyeloureteric system is unique in physiology in that the primary pacemaker resides in a population of atypical SMCs situated near the border of the renal papilla. 2. Atypical SMCs display high-frequency Ca(2+) transients upon the spontaneous release of Ca(2+) from inositol 1,4,5-trisphosphate (IP(3))-dependent stores that trigger cation-selective spontaneous transient depolarizations (STDs). In the presence of nifedipine, these Ca(2+) transients and STDs seldom propagate > 100 mum. Synchronization of STDs in neighbouring atypical SMCs into an electrical signal that can trigger action potential discharge and contraction in the typical SMC layer involves a coupled oscillator mechanism dependent on Ca(2+) entry through L-type voltage-operated Ca(2+) channels. 3. A population of spindle- or stellate-shaped cells, immunopositive for the tyrosine receptor kinase kit, is sparsely distributed throughout the pyeloureteric system. In addition, Ca(2+) transients and action potentials of long duration occurring at low frequencies have been recorded in a population of fusiform cells, which we have termed interstitial cells of Cajal (ICC)-like cells. 4. The electrical and Ca(2+) signals in ICC-like cells are abolished upon blockade of Ca(2+) release from either IP(3)- or ryanodine-dependent Ca(2+) stores. However, the spontaneous Ca(2+) signals in atypical SMCs or ICC-like cells are little affected in W/W(-v) transgenic mice, which have extensive lesions of their intestinal ICC networks. 5. In summary, we have developed a model of pyeloureteric pacemaking in which atypical SMCs are indeed the primary pacemakers, but the function of ICC-like cells has yet to be determined.

An inner medullary concentrating process actuated by renal pelvic/calyceal muscle contractions: assessment and hypothesis.

We propose a mechanism of an inner medullary concentrating process in which water extraction is accomplished by a colloid osmotic mechanism and hydrostatic pressure. There are 3 essential features of the proposal: 1. the fluid compartmental structure of the inner medullary interstitium: owing to molecular exclusion, negatively charged macromolecules, i.e. hyaluronan and extravasated plasma albumin form separate compartments (the HA and the EPA compartments); the resulting Gibbs-Donnan effect governs the movements of both ions and water. 2. NaCl, in high concentration in the inner medulla conditioned by the outer medullary countercurrent processes, significantly reduces the equilibrium colloid osmotic pressure between these compartments. 3. Urea, also accumulated here by special transport mechanisms, increases the mobility of water molecules and the flexibility of the HA fibrils by loosening hydrogen bonds. These features suggest that rhythmic, small pressure increases of the pelvic/calyceal muscles squeeze dilute fluid out of the HA compartment and, at the same time, accelerate the outflow of fluid and albumin into the ascending vasa recta from the EPA compartment. Further, they suggest a mechanism for the phenomenon that living organisms utilize hydrostatic pressure generated by muscle contractions in water economy namely, concentrating and diluting body fluids.

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.

Interdependent regulation of afferent renal nerve activity and renal function: role of transient receptor potential vanilloid type 1, neurokinin 1, and calcitonin gene-related peptide receptors.

Our previous studies have shown that the activation of the transient receptor potential vanilloid type 1 (TRPV1) expressed in the renal pelvis leads to an increase in ipsilateral afferent renal nerve activity (ARNA) and contralateral renal excretory function, but the molecular mechanisms of TRPV1 action are largely unknown. This study tests the hypothesis that activation of receptors of neurokinin 1 (NK1) or calcitonin gene-related peptide (CGRP) by endogenously released substance P (SP) or CGRP following TRPV1 activation, respectively, governs TRPV1-induced increases in ARNA and renal excretory function. Capsaicin (CAP; 0.04, 0.4, and 4 nM), a selective TRPV1 agonist, administered into the renal pelvis dose-dependently increased ARNA. CAP (4 nM)-induced increases in ipsilateral ARNA or contralateral urine flow rate (Uflow) and urinary sodium excretion (UNa) were abolished by capsazepine (CAPZ), a selective TRPV1 antagonist, or 2-[1-imino-2-(2-methoxyphenyl)ethyl]-7,7-diphenyl-4-perhydroisoindolone (3aR,7aR) (RP67580) or cis-2-(diphenylmethyl)-N-[(2-iodophenyl)-methyl]-1 azabicyclo[2.2.2]octan-3-amine (L703,606), selective NK1 antagonists, but not by CGRP8-37, a selective CGRP receptor antagonist. Both SP (7.4 nM) and CGRP (0.13 muM) increased ARNA, Uflow, or UNa, and increases in these parameters induced by CGRP but not SP were abolished by CAPZ. CAP at 4 nM perfused into the renal pelvis caused the release of SP and CGRP, which was blocked by CAPZ but not by RP67580, L703,606, or CGRP8-37. Immunofluorescence results showed that NK1 receptors were expressed in sensory neurons in dorsal root ganglion and sensory nerve fibers innervating the renal pelvis. Taken together, our data indicate that NK1 activation induced by SP release upon TRPV1 activation governs TRPV1 function and that a TRPV1-dependent mechanism is operant in CGRP action.

Conventional high pressure versus newly developed continuous-flow ureterorenoscope: urodynamic pressure evaluation of the renal pelvis and flow capacity.

PURPOSE: We evaluated the pressure and flow relation of a newly developed continuous-flow ureterorenoscope (URS) in comparison with a common ureterorenoscope in an ex-vivo urinary tract model. MATERIALS AND METHODS: Ureterorenoscopies were performed with the newly developed 10.5F continuous-flow URS with separate inflow and outflow channel and a conventional 10.5F URS with a combined inflow and outflow channel. The ex-vivo model consisted of complete urinary tracts of domestic pigs obtained freshly from the slaughterhouse. Both instruments were used in five urinary tracts, and six ureterorenoscopies were performed in each urinary tract. The pressure in the renal pelvis (RP) was measured during each procedure. Height of the irrigation solution above renal level and flow capacity were also documented. RESULTS: The conventional URS showed a correlation of intrapelvic pressure and the height of the irrigation solution above renal level rising from 20+/-3.7 cm H(2)O at a solution level of 20 cm to a plateau pressure of 40+/-3.3 cm H(2)O with a distinct renal influx at a level of 50 cm. The maximum flow capacity at a solution level of 20 cm was 0.2 mL/min rising to a flow capacity of 0.5 mL/min at 40 cm above renal level. The maximum flow capacity for the continuous-flow URS was about 100 times higher, rising from 20 mL/min at a solution level of 20 cm to 70 mL/min at 40 cm above renal level. The intrapelvic pressure was 15+/-2.1 cm H(2)O at a solution level of 20 cm and did not exceed the physiologic renal pressure of 20 cm H(2)O even if the irrigation solution was at a height of 100 cm above renal level. CONCLUSION: The newly developed continuous-flow URS provides a 100 times higher flow capacity while simultaneously preserving the physiologic pressure in the RP compared with the conventional URS. These characteristics will improve visibility and reduce retrograde stone manipulation, operative time, and complications under clinical conditions.

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.

Angiotensin induces the urinary peristaltic machinery during the perinatal period.

The embryonic development of mammalian kidneys is completed during the perinatal period with a dramatic increase in urine production, as the burden of eliminating nitrogenous metabolic waste shifts from the placenta to the kidney. This urine is normally removed by peristaltic contraction of the renal pelvis, a smooth muscle structure unique to placental mammals. Mutant mice completely lacking angiotensin type 1 receptor genes do not develop a renal pelvis, resulting in the buildup of urine and progressive kidney damage. In mutants the ureteral smooth muscle layer is hypoplastic and lacks peristaltic movements. We show that angiotensin can induce the ureteral smooth muscles in organ cultures of wild-type, but not mutant, ureteral tissues and that, in wild-type mice, expression of both renal angiotensin and the receptor are transiently upregulated at the renal outlet at birth. These results reveal a new role for angiotensin in the unique cellular adaptations of the mammalian kidney to the physiological stresses of postnatal life.

TRPV1-mediated diuresis and natriuresis induced by hypertonic saline perfusion of the renal pelvis.

BACKGROUND: The transient receptor potential vanilloid type 1 (TRPV1) channel is known to be activated by multiple stimuli, albeit its role in mediating renal function is largely unknown. This study was designed to test the hypothesis that TRPV1 mediates diuresis and natriuresis induced by hypertonic saline perfusion into the pelvis. METHODS: NaCl or KCl was perfused into the left renal pelvis of rats at a rate without changing renal pelvic pressure. Afferent renal nerve activity (ARNA), urine flow rate (V) and urinary sodium excretion (UNaV) in the presence or absence of selective antagonists of TRPV1, capsazepine (CAPZ), or neurokinin-1 (NK1) receptors, RP67580, were examined. RESULTS: Unilateral renal pelvis perfusion of NaCl at 600 mM, but not 150 or 300 mM, increased ipsilateral ARNA and contralateral V and UNaV, which were blocked by ipsilateral administration of CAPZ or RP67580. In contrast, KCl perfused at 150 or 300 mM, but not 600 mM, increased ipsilateral ARNA and contralateral V and UNaV, which were insensitive to CAPZ. CONCLUSION: Unilateral hypertonic saline perfusion causes contralateral diuresis and natriuresis via TRPV1 or NK1 activation, indicating that these receptors may play a critical role in sensing microenvironmental changes in the renal pelvis to modulate renal function in health and disease.