Impact of Renal Pelvic Denervation on Systemic Hemodynamics and Neurohumoral Changes in a Porcine Model.

INTRODUCTION: The blood pressure (BP) response to arterial renal denervation (RDN) is variable. METHODS: This study examined the effectiveness of renal pelvic denervation (RPD) on BP, heart rate (HR), norepinephrine (NE), and histopathology in 42 swine. NE levels were measured immediately, 7, 14, 30, and 90 days after RPD. Intra-arterial BP and HR were measured throughout RPD and after 14 days in 5 swine. RESULTS: During the procedure, RPD immediately reduced systolic BP (-20.6 ± 18.3 mm Hg), diastolic BP (-6.0 ± 8.3 mm Hg), and HR (-5.4 ± 5.6 bpm), which remained decreased at follow-up. The porcine kidneys had a mean NE reduction of 76% directly post procedure and 60% after 7 days, 64% after 14 days, 57% after 30 days, and 65% after 90 days. Histopathological examination confirmed nerve ablation. CONCLUSIONS: These preliminary findings suggest that the renal pelvis nerve ablation is an encouraging target for RDN. Clinical trials are required to test the feasibility of RPD in human hypertension.

Does glucagon-like peptide-1 induce diuresis and natriuresis by modulating afferent renal nerve activity?

Glucagon-like peptide-1 (GLP-1), an incretin hormone, has diuretic and natriuretic effects. The present study was designed to explore the possible underlying mechanisms for the diuretic and natriuretic effects of GLP-1 via renal nerves in rats. Immunohistochemistry revealed that GLP-1 receptors were avidly expressed in the pelvic wall, the wall being adjacent to afferent renal nerves immunoreactive to calcitonin gene-related peptide, which is the dominant neurotransmitter for renal afferents. GLP-1 (3 µM) infused into the left renal pelvis increased ipsilateral afferent renal nerve activity (110.0 ± 15.6% of basal value). Intravenous infusion of GLP-1 (1 µg·kg-1·min-1) for 30 min increased renal sympathetic nerve activity (RSNA). After the distal end of the renal nerve was cut to eliminate the afferent signal, the increase in efferent renal nerve activity during intravenous infusion of GLP-1 was diminished compared with the increase in total RSNA (17.0 ± 9.0% vs. 68.1 ± 20.0% of the basal value). Diuretic and natriuretic responses to intravenous infusion of GLP-1 were enhanced by total renal denervation (T-RDN) with acute surgical cutting of the renal nerves. Selective afferent renal nerve denervation (A-RDN) was performed by bilateral perivascular application of capsaicin on the renal nerves. Similar to T-RDN, A-RDN enhanced diuretic and natriuretic responses to GLP-1. Urine flow and Na+ excretion responses to GLP-1 were not significantly different between T-RDN and A-RDN groups. These results indicate that the diuretic and natriuretic effects of GLP-1 are partly governed via activation of afferent renal nerves by GLP-1 acting on sensory nerve fibers within the pelvis of the kidney.

H2O2 generated by NADPH oxidase 4 contributes to transient receptor potential vanilloid 1 channel-mediated mechanosensation in the rat kidney.

The presence of NADPH oxidase (Nox) in the kidney, especially Nox4, results in H2O2 production, which regulates Na(+) excretion and urine formation. Redox-sensitive transient receptor potential vanilloid 1 channels (TRPV1s) are distributed in mechanosensory fibers of the renal pelvis and monitor changes in intrapelvic pressure (IPP) during urine formation. The present study tested whether H2O2 derived from Nox4 affects TRPV1 function in renal sensory responses. Perfusion of H2O2 into the renal pelvis dose dependently increased afferent renal nerve activity and substance P (SP) release. These responses were attenuated by cotreatment with catalase or TRPV1 blockers. In single unit recordings, H2O2 activated afferent renal nerve activity in response to rising IPP but not high salt. Western blots revealed that Nox2 (gp91(phox)) and Nox4 are both present in the rat kidney, but Nox4 is abundant in the renal pelvis and originates from dorsal root ganglia. This distribution was associated with expression of the Nox4 regulators p22(phox) and polymerase δ-interacting protein 2. Coimmunoprecipitation experiments showed that IPP increases polymerase δ-interacting protein 2 association with Nox4 or p22(phox) in the renal pelvis. Interestingly, immunofluorescence labeling demonstrated that Nox4 colocalizes with TRPV1 in sensory fibers of the renal pelvis, indicating that H2O2 generated from Nox4 may affect TRPV1 activity. Stepwise increases in IPP and saline loading resulted in H2O2 and SP release, sensory activation, diuresis, and natriuresis. These effects, however, were remarkably attenuated by Nox inhibition. Overall, these results suggest that Nox4-positive fibers liberate H2O2 after mechanostimulation, thereby contributing to a renal sensory nerve-mediated diuretic/natriuretic response.

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.

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.

Distribution of Cajal like cells and innervation in intrinsic ureteropelvic junction obstruction.

OBJECTIVES: C-kit positive interstitial cells of Cajal (ICC)-like cells are defined as pacemaker cells in the ureter, which produce and coordinate peristaltic motility. To investigate the changes in ICC-like cells and innervation in segments of intrinsic uretero-pelvic junction (UPJ) obstruction. MATERIAL AND METHODS: Full thickness specimens obtained from UPJ segments (n = 77) were divided into 3 groups. Group I included 32 intrinsic UPJ obstruction segments, separated into 3 subgroups: Group Ia (proximal), Group Ib (obstruction, intermediate) and Group Ic (distal segments). Group II included 30 normal UPJ segments derived from the nephrectomy specimens. In Group III, 15 UPJ segments of chronic obstruction were analyzed. Formalin fixed, paraffin embedded specimens from UPJs were analyzed immunohistochemically for CD117, S100 and synaptophysin protein expression in nerve plexus and ganglionic cells in the neuromuscular junction. RESULTS: Group Ib showed significantly decreased (p < 0.05) positive staning with c-kit protooncogene protein (CD117), S100 and synaptophysin proteins compared with Group Ia and Group Ic. ICC-like cells were observed in increased number (p < 0.05) in Group Ia compared to Groups II and III. Group Ib had lower synaptophysin positivity compared to Group II. CONCLUSIONS: The findings support the hypothesis of decreased innervation in the etiopathogenesis of intrinsic UPJ obstruction. Increased number of ICC-like cells in Group Ia suggests that peristaltic activity is higher in pelvicalyceal region.

Activation of endothelin A receptors contributes to impaired responsiveness of renal mechanosensory nerves in congestive heart failure.

Increasing renal pelvic pressure results in PGE2-mediated release of substance P, leading to increases in afferent renal nerve activity (ARNA) and natriuresis, that is, a renorenal reflex response. The renorenal reflexes are impaired in congestive heart failure (CHF). Impairment of the renorenal reflexes may contribute to the increased renal sympathetic nerve activity and sodium retention in CHF. Endothelin (ET)-1 contributes to the pathological changes in cardiac and renal function in CHF. Therefore, we examined whether the ETA receptor antagonist BQ123 altered the responsiveness of renal mechanosensory nerves in CHF. The ARNA responses to increasing renal pelvic pressure were suppressed in CHF but not in sham-CHF rats. In CHF, increasing renal pelvic pressure by 7.5 mm Hg before and during renal pelvic perfusion with BQ123 increased ARNA 12% +/- 3% and 21% +/- 3% (p < 0.05 vs. vehicle). In isolated renal pelvises from CHF rats, PGE2 increased substance P release from 5 +/- 0 to 7 +/- 1 pg/min without BQ123 and from 4 +/- 1 to 9 +/- 1 pg/min with BQ123 in the bath (p < 0.01 vs. vehicle). BQ123 had no effect on the ARNA responses or substance P release in sham-CHF. In conclusion, activation of ETA receptors contributes to the impaired responsiveness of renal mechanosensory nerves in CHF rats by a mechanism(s) at the renal sensory nerve endings.

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.

Dietary sodium modulates the interaction between efferent renal sympathetic nerve activity and afferent renal nerve activity: role of endothelin.

Increasing efferent renal sympathetic nerve activity (ERSNA) increases afferent renal nerve activity (ARNA), which in turn decreases ERSNA via activation of the renorenal reflexes in the overall goal of maintaining low ERSNA. We now examined whether the ERSNA-induced increases in ARNA are modulated by dietary sodium and the role of endothelin (ET). The ARNA response to reflex increases in ERSNA was enhanced in high (HNa)- vs. low-sodium (LNa) diet rats, 7,560 +/- 1,470 vs. 900 +/- 390%.s. The norepinephrine (NE) concentration required to increase PGE(2) and substance P release from isolated renal pelvises was 10 pM in HNa and 6,250 pM in LNa diet rats. In HNa diet pelvises 10 pM NE increased PGE(2) release from 67 +/- 6 to 150 +/- 13 pg/min and substance P release from 6.7 +/- 0.8 to 12.3 +/- 1.8 pg/min. In LNa diet pelvises 6,250 pM NE increased PGE(2) release from 64 +/- 5 to 129 +/- 22 pg/min and substance P release from 4.5 +/- 0.4 to 6.6 +/- 0.7 pg/min. In the renal pelvic wall, ETB-R are present on unmyelinated Schwann cells close to the afferent nerves and ETA-R on smooth muscle cells. ETA-receptor (R) protein expression in the renal pelvic wall is increased in LNa diet. In HNa diet, renal pelvic administration of the ETB-R antagonist BQ788 reduced ERSNA-induced increases in ARNA and NE-induced release of PGE(2) and substance P. In LNa diet, the ETA-R antagonist BQ123 enhanced ERSNA-induced increases in ARNA and NE-induced release of substance P without altering PGE(2) release. In conclusion, activation of ETB-R and ETA-R contributes to the enhanced and suppressed interaction between ERSNA and ARNA in conditions of HNa and LNa diet, respectively, suggesting a role for ET in the renal control of ERSNA that is dependent on dietary sodium.

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.

Cyclooxygenase-2 involved in stimulation of renal mechanosensitive neurons.

Stretching of the renal pelvic wall activates renal mechanosensitive neurons, resulting in an increase in afferent renal nerve activity (ARNA). Prostaglandin (PG)E(2) plays a crucial role in the activation of renal mechanosensitive neurons through facilitation of the release of substance P from the sensory neurons in the renal pelvic wall. Because wall stretch may induce cyclooxygenase-2 activity, we examined whether cyclooxygenase-2 was expressed in the renal pelvic wall and whether activation of cyclooxygenase-2 contributed to the ARNA response produced through increased renal pelvic pressure. In situ hybridization showed a strong cyclooxygenase-2 mRNA signal in the papilla and subepithelial layer of the renal pelvic wall from time control kidneys and from kidneys exposed to 15 minutes of increased renal pelvic pressure in anesthetized surgically operated rats. In anesthetized rats, an increase in renal pelvic pressure increased ARNA by 40+/-2% and increased renal pelvic release of PGE(2) from 289+/-46 to 1379+/-182 pg/min (P<0.01). Renal pelvic perfusion with the cyclooxygenase-2 inhibitor etodolac reduced the increases in ARNA and PGE(2) by 66+/-7% and 55+/-13%, respectively (P<0.01). Likewise, the cyclooxygenase-2 inhibitor 5, 5-dimethyl-3-(3-fluorophenyl)-4-(4-methylsulfonyl)phenyl-2(5H)-furanone reduced the increases in ARNA and PGE(2) by 43+/-5% and 47+/-8%, respectively. We conclude that cyclooxygenase-2 is expressed in the renal pelvic wall and that the activation of cyclooxygenase-2 contributes to the stimulation of renal mechanosensitive neurons in the pelvic wall.

Tachykinins and calcitonin gene-related peptide as co-transmitters in local motor responses produced by sensory nerve activation in the guinea-pig isolated renal pelvis.

Electrical field stimulation of circular muscle strips from the guinea-pig isolated renal pelvis produces a frequency-dependent positive inotropic effect of the spontaneous contractions which is unaffected by atropine and guanethidine and abolished by tetrodotoxin or in vitro capsaicin desensitization. Omega conotoxin fraction GVIA markedly inhibited the response to low frequencies of stimulation but had only a partial or minor inhibitory effect at higher frequencies. Tachykinins produce a concentration-dependent positive inotropic effect, neurokinin A being more potent than substance P. On the other hand, rat alpha calcitonin gene-related peptide (CGRP) inhibited spontaneous contractions of the renal pelvis. MEN 10,376 a neurokinin A (4-10) analog, antagonized the positive inotropism produced by neurokinin A, without affecting the response to KCl, and suppressed the positive inotropic response produced by electrical field stimulation. In the presence of MEN 10,376, a negative inotropic response was produced by electrical field stimulation which was antagonized by the C-terminal fragment (8-37) of human alpha calcitonin gene-related peptide (hCGRP). hCGRP (8-37) antagonized the negative inotropic effect of exogenously administered CGRP without affecting inhibition by isoprenaline. Application of capsaicin (10 microM) produced a marked increase in the outflow of substance P-, neurokinin A- and CGRP-like immunoreactivities from the superfused guinea-pig renal pelvis. Substance P-, neurokinin A- and CGRP-like immunoreactivities were also detected in tissue extracts of the renal pelvis by radioimmunoassay. These experiments indicate that peptide release from peripheral endings of capsaicin-sensitive primary afferents represents the major type of nerve-mediated response affecting motility of the guinea-pig isolated renal pelvis. Tachykinins and CGRP act as physiological antagonists and the excitatory action of tachykinins prevails over the inhibitory action of CGRP. Local modulation of renal pelvis motility by sensory nerves could facilitate removal of irritants present in the urine, protecting the kidney during obstruction and ureteral antiperistalsis.

Stimulation of neuropeptide release from sensory and enteric neurons in the guinea-pig by alpha-latrotoxin.

alpha-Latrotoxin, from black widow spider venom, stimulates exocytosis of small synaptic vesicles at central and peripheral synapses. However, it is widely accepted that neuropeptide-containing large dense-core vesicles are insensitive to the toxin. In the present study, we investigated whether alpha-latrotoxin releases neuropeptides from primary afferent and enteric neurons. The guinea-pig renal pelvis is innervated by primary sensory neurons containing tachykinins and calcitonin gene-related peptide, but has no functional cholinergic or noradrenergic motor innervation. alpha-Latrotoxin increased the amplitude of spontaneous myogenic contractions of the renal pelvis, and this effect was prevented by prior capsaicin desensitization and by antagonists at neurokinin-1 and neurokinin-2 receptors. In the presence of the latter antagonists, alpha-latrotoxin decreased the amplitude of the contractions, and this is likely to be mediated by calcitonin gene-related peptide. Thus, alpha-latrotoxin releases tachykinins and calcitonin gene-related peptide from capsaicin-sensitive sensory neurons in the renal pelvis. The circular muscle of the guinea-pig distal colon is innervated by excitatory and inhibitory motor neurons, which use a number of transmitters. In the presence of antagonists to block each of the known transmitters apart from the tachykinins, alpha-latrotoxin increased the amplitude of spontaneous contractions; this effect was prevented by the prior addition of neurokinin-1 and neurokinin-2 receptor antagonists. Thus, alpha-latrotoxin stimulates the release of tachykinins from excitatory motor neurons in the myenteric plexus of the distal colon. In conclusion, this study demonstrates that alpha-latrotoxin is able to evoke the release of neuropeptides from both sensory and enteric neurons. This suggests that exocytosis of large dense-core vesicles shares more of the features of exocytosis of small synaptic vesicles than has previously been appreciated.

Neurokinin A in rat renal afferent neurons and in nerve fibres within smooth muscle and epithelium of rat and guinea-pig renal pelvis.

Neurokinin A-like immunoreactivity of dorsal root ganglion neurons innervating the kidney were studied with retrograde tracing of FluoroGold dye applied to the cut renal nerves. The proportions and sizes of renal afferent neurons with neurokinin A-like immunoreactivity were quantified in T9-L2 dorsal root ganglia from five rats. Of 240 renal afferent neuronal somata examined, 26 +/- 3% (S.E.M.) showed neurokinin A-like immunoreactivity. Compared with the overall size distribution of renal afferent neurons, those staining for neurokinin A were mostly small-sized neurons with a few medium-sized neurons. All somata with neurokinin A-like immunoreactivity were neurofilament-poor as judged by labelling with an anti-neurofilament antibody, RT97, and it is therefore likely that they had unmyelinated fibres. To examine the sites to which the renal afferent fibres with neurokinin A might project, sections of rat and guinea-pig kidney and upper ureter were examined. Fibres with neurokinin A-like immunoreactivity were found beneath and within the transitional epithelium lining the inner surface of the pelvis, and within the smooth muscle layer beneath the transitional epithelium. Epithelial innervation was found only in regions with underlying smooth muscle and loose connective tissue, and not in sites where the epithelium was closely applied to the renal parenchyma. The network of fibres was most dense towards the pelvo-uretic junction. Fibres with neurokinin A-like immunoreactivity were not seen beneath or within the cuboidal/columnar epithelium covering the papilla within the renal pelvis. Furthermore, only very few fibres with neurokinin A were observed penetrating the transitional epithelium of the upper ureter in both rat and guinea-pig. The distribution of fibres labelled with antibodies to substance P and calcitonin gene-related peptide in the renal pelvis was similar to that for fibres with neurokinin A-like immuno-reactivity, although a few fibres penetrated further into the fornices than fibres with neurokinin-A-like immunoreactivity. Thus, many afferent fibres in the renal pelvis may contain neurokinin A as well as substance P and calcitonin gene-related peptide. These fibres may be the source of the neurokinin A, substance P and calcitonin gene-related peptide which can be released by topical capsaicin treatment. In addition they may be the mechano- and chemo-receptive fibres in the renal pelvis that are known to play important roles in renal haemodynamics. The intra-epithelial position of some of these fibres in the epithelial layer suggests a possible chemosensory or osmosensory role.

Tachykinin receptors in the guinea-pig renal pelvis: activation by exogenous and endogenous tachykinins.

1. The contractile response to substance P, neurokinin A, selective agonists for the NK1, NK2 and NK3 tachykinin receptors and the activity of receptor-selective antagonists has been investigated in circular muscle strips of the guinea-pig isolated renal pelvis in the presence of indomethacin (3 microM). 2. Neurokinin A was the most potent agonist tested, being about 32 times more potent than substance P. The action of both substance P and neurokinin A was enhanced by peptidase inhibitors (bestatin, captopril and thiorphan, 1 microM each). The selective NK2 receptor agonist [beta Ala8] neurokinin A (4-10), was slightly less potent and effective than neurokinin A itself. The selective NK1 receptor agonist [Sar9] substance P sulphone was effective at low (nM) concentrations but its maximal effect did not exceed 30% of maximal response to substance P or neurokinin A. The NK3-selective agonist [MePhe7] neurokinin B was effective only at high (microM) concentrations. 3. The pseudopeptide derivative of neurokinin A(4-10), MDL 28,564, displayed a clear-cut agonist character, although it was less potent than neurokinin A. 4. The responses to roughly equieffective (25-35% of maximal response) concentrations of [beta Ala8] neurokinin A (4-10), MDL 28,564 and [MePhe7] neurokinin B were antagonized to a similar extent by MEN 10,376 (3 microM), a selective NK2 tachykinin receptor antagonist, while the response to [Sar9] substance P sulphone was unchanged. 5. The response to [Sar9] substance P sulphone was inhibited by the NK1 receptor-selective antagonist, GR 82,334 (3 microM) while the response to [beta Ala8] neurokinin A (4-10) was unchanged. 6. The selective NK2 receptor antagonists MEN 10,376, L 659,877 and R 396 antagonized competitively the response to [PAla8] neurokinin A (4-10) with the following rank order of potency (pA2 values in parentheses): MEN 10,376 (7.41)>L 659,877 (7.15)>R 396 (6.43). MEN 10,376 and L 659,877 also competitively antagonized the response to neurokinin A, although with lower potency as compared to the selective NK2 receptor agonist.7. MEN 10,376, L 659,877 and R 396 reduced in a concentration-dependent manner the contractile response produced by electrical field stimulation (1 Hz, 100 V, 0.25 ms pulse width, trains of 10 s). The rank order of potency of NK2 receptor antagonists in blocking the response to electrical stimulation (MEN 10,376> L 659,877> R 396) closely mimicked their potency in antagonizing exogenous tachykinins.8. The inhibitory effect of MEN 10,376 toward responses produced by electrical field stimulation was significantly reduced when tested in the presence of peptidase inhibitors, which increased significantly the response to nerve stimulation.9. GR 82,334 (3 pM) did not significantly affect the response to nerve stimulation in untreated preparations and slightly reduced it in the presence of peptidase inhibitors.10. We conclude that both NK, and NK2 receptors mediate the contractile effect of tachykinins in the circular muscle of the guinea-pig renal pelvis and that the response ascribable to NK2 receptor stimulation is larger than that ascribed to NK, receptor stimulation. The NK2 receptor in the guinea-pig renal pelvis belongs to the same subtype previously identified in the rabbit pulmonary artery. NK2 receptors play a dominant role in the physiological response determined by the release of endogenous tachykinins and a contribution of NKI receptors becomes evident after inhibition of peptide degradation.

Simultaneous histochemical demonstration of noradrenergic nerves and tissue components in guinea-pig renal pelvis after treatment with daunomycin.

A standard histochemical technique for detecting catecholamines has been applied to tissues from the renal pelvis of untreated and daunomycin-pretreated guinea-pigs. Under the fluorescence microscope, muscular, mucosal, and endothelial cells exhibited the drug-specific orange-red fluorescence, in contrast to the dark background of control tissues. The presence of daunomycin in the cells also greatly improved the visibility of numerous noradrenergic fibres which appeared to originate from perivascular plexuses and distribute to the smooth cells. A dense noradrenergic innervation was detected in the submucosa, but the epithelium did not contain any yellow-green fluorescent fibres. A typical arrangement was observed consisting of muscular, nervous and vascular components, enveloped by connective tissue: this formation appeared to be related to the system modulating the pacemaker activity of the renal pelvis.

Study of tyrosine hydroxylase and neuropeptidergic innervation of the human obstructed pelveoureteral junction in four different patients.

Tyrosine hydroxylase and neuropeptidergic innervations of the obstructed pelveoureteral junctions of four different patients were investigated by immunohistochemical methods. A dense innervation of tyrosine hydroxylase- and neuropeptide Y-nerves was found especially in the pelveoureteral junction, which was congenitally obstructed, compared to others found later (13- and 23-year old females). Also quite numerous vasoactive intestinal polypeptide-nerves were seen as well as some calcitonin gene-related peptide-, galanin- and substance P-nerves in the muscular layer of ureter. The innervation pattern of the obstructed pelveoureteral junction of the horseshoe kidney was found to be normal.

[Anatomy and function of the upper urinary tract].

This report deals with the histologic and gross anatomy of the upper urinary tract (calyces, pelvis, and ureter) as well as the nerve supply to this region. It also covers the physiological transport of urine from the kidneys to the bladder, which is reviewed on the basis of experimental and clinical studies. A pacemaker system present in the proximal calyces has been found to have an important physiological role in urine transport. However, clinical experience has shown that urine transport is not affected by surgery such as pyeloplasty and pyelolithotomy which impairs the activity of this pacemaker. Electron microscopic and histochemical studies as well as the maintenance of urine transport after renal grafting suggest that the nerve supply to the upper urinary tract is not dominant in regard to this function. This study also investigated urinary transportation in the presence of urinary tract obstruction due to various diseases, and demonstrated that urine is also conveyed by gravity and not solely by ureteric peristalsis. The use of internal stenting and percutaneous urinary diversion thus appears to be reasonable. Although the detailed etiology congenital hydronephrosis is still unknown, there is no doubt that it involves dysfunction of the ureteropelvic junction, since urine transport is improved by the endoscopic or surgical formation of a physiological tunnel at this junction which can regulate the volume of urine transported according to urine output. It is important for studies of upper urinary tract function to be conducted in close relation to clinical practice and not to simply be confined to esoteric experimental situations.

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.

A novel non-vascular system to treat resistant hypertension.

AIMS: To evaluate in a preclinical model the utility of a monopolar electrode catheter delivering radiofrequency (RF) energy placed into the renal pelvis in order to treat resistant hypertension (RH). METHODS AND RESULTS: Sixteen female domestic swine weighing 60-65 kg underwent renal pelvic denervation via ureteral access. Three animals were euthanised immediately after delivery of RF energy; five animals were allowed to survive for seven days, six animals were allowed to survive for 14 days and two animals were allowed to survive for 30 days. Renal cortical norepinephrine levels were measured in all groups of animals. Histopathology of the treated zone was performed to confirm nerve damage. Renal cortical tissue was harvested for determination of tissue norepinephrine by HPLC. The kidneys were then profusion-fixed and harvested for histopathologic analysis. Mean reduction of norepinephrine levels was 60.4% compared to control. Histopathology confirmed nerve ablation in the treated zone. CONCLUSIONS: In this small, preclinical study, we introduce a new non-vascular system to treat resistant hypertension. If the current clinical experience confirms efficacy and safety, this approach may be one way to treat patients who cannot be treated with the standard percutaneous arterial devices.