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.

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.

Smooth Muscle Cell Apoptosis and Defective Neural Development in Congenital Ureteropelvic Junction Obstruction

PURPOSE

We assessed the smooth muscle cell apoptosis along with changes in cellular and extracellular components of the ureteropelvic junction in 23 patients with unilateral obstruction and compared them with 25 autopsies from ureteropelvic junction regions of age matched cadavers.

MATERIALS AND METHODS

Tissue specimens obtained from pyeloplasty were divided into 3 sections-renal pelvis above the obstruction, obstructed ureteropelvic junction and ureter below the obstructed region. For the control group the normal ureteropelvic junctions of age matched infants were autopsied. In paraffin embedded sections we determined myocyte apoptosis index (using TUNEL assay), and the amount of muscular components and nerve terminals (using image analysis techniques after immunohistochemical staining). The collagen and elastin fibers were specifically stained for evaluation of changes in extracellular matrix.

RESULTS

Smooth muscle cell apoptosis index was significantly increased at the site of ureteropelvic junction obstruction (5.68 +/- 0.18) compared to normal autopsied ureteropelvic junctions (3.60 +/- 0.11) and 2 other sections of obstructed ureteropelvic junction complex (renal pelvis 4.73 +/- 0.16, and ureter 3.97 +/- 0.16). The number of nerve terminals and the percentage of muscular component were significantly lower at the obstructed segments of affected patients compared to normal ureteropelvic junctions. Meanwhile, collagen fibers formed a significantly higher proportion of ureteral wall at the site of obstruction. Interestingly, there was negative correlation between myocyte apoptosis indices and number of nerve endings as well as amount of muscular components at the site of ureteropelvic junction obstruction. However, positive correlations were found between smooth muscle cell apoptosis and the percentage of collagen and elastin fibers.

CONCLUSIONS

Our findings suggest an important role for myocyte apoptosis and defective neural development in the pathogenesis of congenital ureteropelvic junction obstruction that could pave the road for the emergence of new therapeutic modalities.

Diuresis and Natriuresis Caused by Activation of VR1-Positive Sensory Nerves in Renal Pelvis of Rats

To test the hypothesis that activation of the vanilloid receptor 1 (VR1) expressed in sensory nerves innervating the renal pelvis leads to diuresis and natriuresis, a selective VR1 receptor agonist, capsaicin (2.4 nmol), or vehicle was perfused intravenously or into the left renal pelvis of anesthetized rats at a rate without changing renal perfusion pressure. Mean arterial pressure was not altered by capsaicin administered intravenously or into the renal pelvis. Capsaicin perfusion into the left renal pelvis but not intravenously caused significant increases in urine flow rate and urinary sodium excretion bilaterally in a dose-dependent manner, which were abolished by capsazepine, a selective VR1 receptor antagonist, given ipsilaterally to the renal pelvis or by ipsilateral renal denervation. Capsaicin given intravenously or into the left renal pelvis increased plasma calcitonin gene-related peptide levels to the same extent. Increased plasma calcitonin gene-related peptide levels induced by capsaicin (68.9±2.8 pg/mL) perfusion into the renal pelvis was prevented either by capsazepine (22.5±10.1 pg/mL) given ipsilaterally into the renal pelvis or by ipsilateral renal denervation (25.9±2.3 pg/mL). Taken together, our data show that unilateral activation of VR1-positive sensory nerves innervating the renal pelvis leads to bilateral diuresis and natriuresis via a mechanism that is independent of plasma calcitonin gene-related peptide levels. These data suggest that VR1-positive sensory nerves in the kidney enhance renal excretory function, a mechanism that may be critically involved in sodium and fluid homeostasis.

Impaired substance P release from renal sensory nerves in SHR involves a pertussis toxin-sensitive mechanism

Stretching the renal pelvic wall activates renal mechanosensory nerves by a PGE2-mediated release of substance P via activation of the cAMP-PKA pathway. Renal pelvic ANG II modulates the responsiveness of renal sensory nerves by suppressing the PGE2-mediated activation of adenylyl cyclase via a pertussis toxin (PTX)-sensitive mechanism. In SHR, activation of renal mechanosensory nerves is impaired. This is due to suppressed release of substance P in response to increased pelvic pressure. The present study was performed to investigate whether the PGE2-mediated release of substance P was suppressed in SHR vs. WKY and, if so, whether the impaired PGE2-mediated release of substance P was due to ANG II activating a PTX-sensitive mechanism. In an isolated renal pelvic wall preparation, PGE2, 0.14 μM, increased substance P release from 9 ± 3 to 22 ± 3 pg/min ( P < 0.01) in Wistar-Kyoto rats (WKY), but had no effect in spontaneously hypertensive rats (SHR). A tenfold higher concentration of PGE2, 1.4 μM, was required to increase substance P release in SHR, from 7 ± 1 to 22 ± 3 pg/min ( P < 0.01). In SHR, treating renal pelvises with losartan enhanced the release of substance P produced by subthreshold concentration of PGE2, 0.3 μM, from 16 ± 2 to 26 ± 3 pg/min ( P < 0.01). Likewise, treating renal pelvises with PTX enhanced the PGE2-mediated release of substance P from 10 ± 1 to 33 ± 3 pg/min ( P < 0.01) in SHR. In WKY, neither losartan nor PTX had an effect on the release of substance P produced by subthreshold concentrations of PGE2, 0.03 μM. In conclusion, the impaired responsiveness of renal sensory nerves in SHR involves endogenous ANG II suppressing the PGE2-mediated release of substance P via a PTX-sensitive mechanism.

Angiotensin blocks substance P release from renal sensory nerves by inhibiting PGE2-mediated activation of cAMP

Activation of renal sensory nerves involves PGE2-mediated release of substance P (SP) via activation of the cAMP-PKA pathway. The PGE2-mediated SP release is suppressed by a low- and enhanced by a high-sodium (Na+) diet, suggesting an inhibitory effect of ANG. We now examined whether ANG II is present in the pelvic wall and inhibits PGE2-mediated SP release by blocking PGE2-mediated increases in cAMP. ANG II levels in renal pelvic tissue were 710 +/- 95 and 260 +/- 30 fmol/g tissue in rats fed a low- and high-Na+ diet, respectively. In a renal pelvic preparation from high-Na+-diet rats, 0.14 microM PGE2 produced an increase in SP release from 7 +/- 1 to 19 +/- 3 pg/min that was blocked by 15 nM ANG II. Treating pelvises with pertussis toxin (PTX) abolished the effects of ANG II. In pelvises from low-Na+ rats, neither basal nor bradykinin-mediated SP release was altered by PGE2. However, the bradykinin-mediated release of SP was enhanced by the permeable cAMP analog CPT-cAMP, from 4 +/- 1 to 11 +/- 2 pg/min, a response similar to that in normal-Na+-diet rats. In vivo, renal pelvic administration of PGE2 enhanced the afferent renal nerve activity (ARNA) response to bradykinin in normal- but not in low-Na+ diet rats. CPT-cAMP produced similar enhancement of the ARNA responses to bradykinin in normal- and low-Na+-diet rats, 1,670 +/- 490 and 1,760 +/- 400%.s (area under the curve of ARNA vs. time). Similarly, the ARNA responses to increases in renal pelvic pressure were similarly enhanced by CPT-cAMP in normal- and low-Na+-diet rats. In conclusion, renal pelvic ANG II modulates the responsiveness of renal sensory nerves by suppressing PGE2-mediated activation of adenylyl cyclase via a PTX-sensitive mechanism.

Demonstration of nitrergic and cholinergic innervation in whole-mount preparations of rabbit, pig, and human upper urinary tract

To investigate the distribution of nitrergic and cholinergic innervation in rabbit, pig, and human upper urinary tract, (UUT) whole-mount preparations and frozen sections were stained with nicotinamide adenine dinucleotide phosphate (NADPH)-diaphorase and acetylcholinesterase (AChE) histochemistry. NADPH-diaphorase and AChE staining demonstrated two neuronal plexuses in the submucous and muscular layer of the UUT in all three species. The presence of nitrergic and cholinergic neuronal networks in the normal UUT suggests that autonomic innervation may play an important role in the transmission of ureteral peristalsis.

PGE(2) increases release of substance P from renal sensory nerves by activating the cAMP-PKA transduction cascade

Increasing renal pelvic pressure increases afferent renal nerve activity (ARNA) by a PGE(2)-mediated release of substance P (SP) from renal pelvic nerves. The role of cAMP activation in the PGE(2)-mediated release of SP was studied by examining the effects of the adenylyl cyclase (AC) activator forskolin and AC inhibitor dideoxyadenosine (DDA). Forskolin enhanced the bradykinin-mediated release of SP from an isolated rat renal pelvic wall preparation, from 7.3 +/- 1.3 to 15.6 +/- 3.0 pg/min. PGE(2) at a subthreshold concentration for SP release mimicked the effects of forskolin. The EP(2) receptor agonist butaprost, 15 microM, and PGE(2), 0.14 microM, produced similar increases in SP release, from 5.8 +/- 0.8 to 17.0 +/- 2.3 pg/min and from 8.0 +/- 1.3 to 21.6 +/- 2.7 pg/min. DDA blocked the SP release produced by butaprost and PGE(2). The PGE(2)-induced release of SP was also blocked by the PKA inhibitors PKI(14-22) and H-89. Studies in anesthetized rats showed that renal pelvic administration of butaprost, 10 microM, and PGE(2), 0.14 microM, resulted in similar ARNA responses, 1,520 +/- 390 and 1,170 +/- 270%. s (area under the curve of ARNA vs. time) that were blocked by DDA. Likewise, the ARNA response to increased renal pelvic pressure, 7,180 +/- 710%. s, was blocked by DDA. In conclusion, PGE(2) activates the cAMP-PKA pathway leading to a release of SP and activation of renal pelvic mechanosensory nerve fibers.

Demonstration of neuronal networks in the human upper urinary tract using confocal laser scanning microscopy

PURPOSE

To our knowledge innervation of the upper urinary tract and its role in motility and sensation are not clearly understood. The whole mount preparation technique provides 3-dimensional (D) morphology of the innervation and its relationship of branching and interconnecting nerve fibers to each other and to the neighboring tissues. Confocal laser scanning microscopy provides dramatic optical advantages for detecting 3-D structures in thick specimens. We investigated the distribution and morphology of the neuronal structures in the human upper urinary tract using the whole mount preparation technique and confocal laser scanning microscopy.

MATERIALS AND METHODS

Whole mount preparations of the human renal pelvis and ureter were stained by standard immunohistochemical method using various neuronal markers (protein gene product 9.5, neuron specific enolase and neurofilament). The 3-D architecture of the specimens was investigated with the help of confocal laser scanning microscopy.

RESULTS

We detected 2 mesh-like neuronal networks or plexus in the human upper urinary tract. The first and more prominent plexus was located in the submucosa between the lamina propria and tunica muscularis, and the second neuronal network was found between the smooth muscle fibers of the ureteral wall. There were frequent interconnections between the 2 networks in the ureteral wall.

CONCLUSIONS

To our knowledge our study shows for the first time that there are 2 well formed mesh-like neuronal plexus in the human upper urinary tract. Our findings suggest that the autonomic nervous system of the human upper urinary tract may have a significant role in the propagation, coordination and modulation of ureteropelvic peristalsis.

Pelviureteral inhibitory reflex and ureteropelvic excitatory reflex: role of the two reflexes in regulation of urine flow from the renal pelvis to the ureter

The mechanism by which the ureteropelvic junction (UPJ) regulates the passage of urine from the renal pelvis to the ureter, and prevents urinary backflow from the the ureter to the renal pelvis, is not completely understood. The current communication studies this mechanism in 18 dogs. With the dogs under anesthesia, nephrostomy was done through which two catheters (one pressure and one balloon-tipped) were introduced into the UPJ and the renal pelvis, respectively. Renal pelvis distension with a balloon filled with 1 ml of saline effected a rise of renal pelvic pressure from a mean basal pressure of 4.8 +/- 1.2 cm H2O to 6.9 +/- 2.3 cm H2O (P < 0.05). The basal UPJ pressure of 12.6 +/- 2.7 cm H2O showed no significant change with 1 ml distention of the renal pelvic balloon (P > 0.05). Renal pelvic distension with 2, 3, and 4 ml caused a significant rise of renal pelvic pressure to 8.4 +/- 2.7 (P < 0.05), 10.6 +/- 2.2 (P < 0.01), and 11.8 +/- 1.9 (P < 0.01) cm H2O, respectively, and a significant drop of UPJ pressure to 4.8 +/- 1.2, 4.7 +/- 1.1, and 4.6 +/- 1.2 cm H2O (P < 0.01), respectively. Ureteric distension with a balloon filled with 0.5 ml of saline significantly raised the ureteric pressure from a mean basal value of 4.3 +/- 1.4 cm H2O to 14.7 +/- 3.3 cm H2O (P < 0.01) and the UPJ pressure to a mean of 20.8 +/- 3.8 (P < 0.05). Ureteric distension with 1 and 1.5 ml of saline led to an elevation of ureteric and UPJ pressure which was not significantly different from that observed with distension with 0.5 ml (P > 0.05). In contrast, the UPJ showed no significant pressure change upon distension of the locally anesthetized renal pelvis or ureter, respectively. Likewise, the locally anesthetized UPJ exhibited no significant pressure response to renal pelvic or ureteric distension. The study demonstrates that urine might have to accumulate in the renal pelvis up to a certain volume and pressure so as to effect UPJ opening, which occurs at its maximum irrespective of the distending volume. UPJ opening upon renal pelvic distension postulates a reflex relationship which we call "pelviureteral inhibitory reflex." This reflex is believed to regulate the passage of urine from the renal pelvis to the ureter. Ureteric distension closes the UPJ; we call this reflex action the "ureteropelvic excitatory reflex" as it seems to prevent reflux of urine through the UPJ and thus protects the kidney. The concept that the UPJ acts as a physiologic sphincter is put forward.

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.

Activation of renal pelvic chemoreceptors in rats: role of calcitonin gene-related peptide receptors

Substance P and calcitonin gene-related peptide (CGRP) increase afferent renal nerve activity (ARNA). A substance P receptor antagonist but not a CGRP receptor antagonist, h-CGRP (8-37), blocks the ARNA response to renal mechanoreceptor (MR) stimulation. We have examined whether calcitonin gene-related peptide activates renal pelvic sensory receptors and whether such activation contributes to renal chemoreceptor stimulation. The calcitonin gene-related peptide receptor antagonist, h-CGRP (8-37) [0.01-10 micromol L-1] dose-dependently decreased (29 +/- 4-86 +/- 13%, P < 0.01) the ipsilateral afferent renal nerve activity in response to the renal pelvic administration of calcitonin gene-related peptide (0.26 micromol L-1). Renal pelvic perfusion with 900 mM NaCl also increased ipsilateral ARNA (23 +/- 3% increase, P < 0.02) and contralateral urinary sodium excretion (13 +/- 4% increase, P < 0. 05). However, these responses to hypertonic NaCl were unaltered by h-CGRP (8-37). Renal pelvic perfusion with 1 or 10 microM h-CGRP (8-37) also failed to alter the ARNA responses to KCl (31.25, 62.5 and 125 mM). These results indicate that there are sensory receptors in the renal pelvic area that are responsive to calcitonin gene-related peptide. The activation of these receptors elicits a contralateral natriuretic response. In contrast, the activation of renal calcitonin gene-related peptide receptors does not contribute to renal chemoreceptor activation.

Immunohistochemical detection of neuronal plexuses and nerve cells within the upper urinary tract of pigs

OBJECTIVE

To investigate the distribution and topography of nervous structures within the renal pelvis and upper part of the ureter of pigs, and thus help to determine the origin, propagation and mechanisms of the modulation of pelvi-ureteric peristalsis.

MATERIALS AND METHODS

Whole-mount preparations of renal pelves from adult pigs were stained using a universal immunostaining method with streptavidin-alkaline phosphatase. Anti-neuron-specific enolase antibody and anti-neurofilament antibody were used as neuronal markers.

RESULTS

The patterns of neuronal structures differed between the renal calyces, renal pelvis and upper ureter. In the calyx, there was one single dense nerve plexus; this network contained relatively thin nerve fibres running both circularly and longitudinally. In the wall of the renal pelvis and upper ureter there were two neuronal plexuses, one submucosal and another within the muscular layer; these nerve fibres were mainly orientated longitudinally. Some single nerve cells were also found at the pelvicalyceal border.

CONCLUSIONS

These findings suggest a potent nervous system within the upper urinary tract of pigs that connects the renal calyces with the renal pelvis, pelvi-ureteric junction and ureter. The presence of these dense neuronal networks and nerve cells within the wall of the renal pelvis and ureter suggests that propagation, coordination and modulation of pelvi-ureteric peristalsis in pigs may arise through intrinsic nervous stimulation.

PGE2 increases substance P release from renal pelvic sensory nerves via activation of N-type calcium channels

Activation of renal pelvic sensory nerves by increased pelvic pressure results in a renal pelvic release of substance P that is dependent on intact prostaglandin synthesis. An isolated renal pelvic wall preparation was used to examine whether PGE2 increases the release of substance P from renal pelvic sensory nerves and by what mechanisms. The validity of the model was tested by examining whether 50 mM KCl increased substance P release from the pelvic wall. Fifty millimolar KCl produced an increase in substance P release, from 9.6 +/- 1.6 to 26.8 +/- 4.0 pg/min, P < 0.01, that was blocked by the L-type calcium blocker verapamil (10 microM). PGE2 (0.14 microM) increased the release of substance P from the pelvic wall from 8.9 +/- 0.9 to 20.6 +/- 3.3 pg/min, P < 0.01. PGE2 failed to increase substance P release in a calcium-free medium. The PGE2-induced substance P release was blocked by the N-type calcium blocker omega-conotoxin (0.1 microM) but was unaffected by verapamil. In conclusion, PGE2 increases the release of substance P from renal pelvic sensory nerves by a calcium-dependent mechanism that requires influx of calcium via N-type calcium channels.

Effect of renal pelvic distension on the ureteropelvic and ureterovesical junctions and the urinary bladder: the renal pelvivesical reflex

For investigation of the effect of distension of the renal pelvis on the ureteropelvic (UPJ) and ureterovesical junctions (UVJ) and on the urinary bladder, nephrostomy was performed on 14 anesthetized mongrel dogs. The pressure was measured in the UPJ by a catheter with a side port introduced through the nephrostomy and in the UVJ and urinary bladder by two catheters inserted cystoscopically. Likewise, a balloon mounted on the tip of a catheter was introduced into the renal pelvis. It was filled with saline in increments of 1 ml, and the pressure response of the UPJ, the UVJ, and the urinary bladder was determined. The test was repeated on the anesthetized renal pelvis, UVJ, and bladder. Whereas renal pelvic distension with 1 ml of saline effected no pressure response in the UPJ, UVJ or bladder, distension with 2-4 ml produced a significant pressure drop (P < 0.01, P < 0.01, and P < 0.05. respectively). There was no difference in the pressure drops recorded at distensions with 2, 3, or 4 ml of saline (P > 0.05). Distension of the anesthetized renal pelvis produced no pressure response in the UPJ, UVJ, or bladder. Furthermore, renal pelvic distension did not elicit a pressure response in the anesthetized UPJ or the bladder. In conclusion, the opening of the UVJ synchronously with the UPJ upon renal pelvic distension appears to assist the delivery of urine from the renal pelvis to the urinary bladder and to protect both the renal pelvis and the ureter against dilatation. This process is supported by a vesical pressure drop. The opening of the UPJ together with the UVJ and the vesical relaxation observed on renal pelvic distension seem to be reflex in nature. A "renal pelvivesical reflex" is postulated to regulate the flow of urine from the renal pelvis to the urinary bladder, preventing the occurrence of urine collection in, or backflow into, the renal pelvis or the ureter.

Structural changes of collagen components and diminution of nerves in congenital ureteropelvic junction obstruction

PURPOSE

Three-dimensional arrangements of smooth muscle cells, collagenous component and peripheral nerves of congenital ureteropelvic junction (UPJ) obstruction were studied in order to clarify the pathogenetic mechanism of interaction among these neuro-myo-stromal components.

MATERIALS AND METHODS

The UPJ and upper ureters were obtained from 14 patients with congenital hydronephrosis (7 intrinsic and 4 extrinsic obstruction) and 7 normal controls. Three-dimensional arrangement of each structural component was observed by scanning electron microscopy, and the nerve distribution was analyzed with immunohistochemistry for protein gene product 9.5.

RESULTS

The UPJ of intrinsic obstruction had structural features as follows. Muscle fascicles were sparse and thin. Each muscle cell was thin in diameter. Intercellular spaces were six to seven times wider than controls. Collagen fibrillar sheaths of smooth muscle cells (pericellular collagen fibrils attached to the basement membrane) were interwoven to form a dense felt-like structure against thin lace-like sheaths in controls. Interstitial collagenous component showed dense and compact structure against loose network of wavy collagen bundles in controls. In the muscular layer, nerve distribution was decreased to about one-third of controls. In contrast, non-stenotic portion of intrinsic UPJ obstruction as well as materials from extrinsic UPJ obstruction showed no structural difference as compared with controls.

CONCLUSIONS

In the intrinsic obstruction, nerve fibers were depleted in the muscular layers in the ureteric walls, resulting in dysfunction and atrophy of muscle fibers and an increase of collagen fibers in the muscle layers with abnormal accumulation of intercellular and interstitial collagen. These changes may disrupt the mobility of UPJ and lead to both mechanical and functional obstruction.

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.

Spatial and temporal variations in pacemaking and conduction in the isolated renal pelvis

In renal pelvis preparations isolated from the sheep, the location of the pacemaker and the pathway of conduction of the electrical impulse in the pelvis were analyzed in detail. An electrophysiological acquisition system was used allowing simultaneous recordings from 240 extracellular electrodes. Reconstruction of the spread of activity showed that the site of the pelvis pacemaker was, in virtually all cases, located at the pelvicalyceal border and never in the body of the pelvis or in the area of the pelviureteric junction. One single pacemaker was responsible for a particular spread of activation, and fusion of activity originating from two or more pacemakers did not place. Furthermore, spontaneous shifts of the pacemaker could occur from one site to another along the pelvicalyceal border. Conduction from the site of the current pacemaker to the pelviureteric junction and the ureter was slow, inhomogeneous, and contorted. Multiple instances of partial or total conduction block were seen at all levels in the pelvis and were not restricted to the pelviureteric junction. The occurrence of the conduction block did not seem to be related to the length of the preceding interval, implying that the refractory period did not play a major role in the genesis of intrapelvic conduction block. In conclusion, high-resolution mapping of the renal pelvis is possible and reveals location and behavior of the pacemaker and documents inhomogeneities in conduction and conduction block.

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.

Effects of nerve stimulation on the spontaneous action potentials recorded in the proximal renal pelvis of the guinea-pig

The effects of nerve stimulation on the electrical and mechanical activity of the smooth muscle of the proximal renal pelvis of the guinea-pig were investigated using standard tension and microelectrode recording techniques. Spontaneous action potentials were deemed to have been recorded from three cell types: (1) "pacemaker" cells (9 of > 120) had membrane potentials (MPs) of -42.1 +/- 2.9 mV and fired action potentials of a simple waveform; (2) "driven" cells (> 100) had more stable MPs of -56.1 +/- 1.2 mV (n = 36) and more complex "ureter-like" action potentials; (3) the remaining cells had MPs of -45.5 +/- 1.7 mV (n = 15) and action potentials with a waveform "intermediate" to groups (1) and (2). Nifedipine (0.1-1 microM) and Cd2+ (0.1-1 mM) blocked all spontaneous action potential discharge and depolarized the membrane to near -40 mV. Intramural nerve stimulation (10-50 Hz for 1-10 s) increased both the amplitude and frequency of the spontaneous contractile activity, this increase peaked in about 30 s and decayed slowly over several minutes. Nerve stimulation depolarized pacemaker and driven cells 9.1 +/- 3.5 (n = 3) and 1.6 +/- 0.7 (n = 6) mV, respectively; the frequency of their action potential discharge increased from 7.6 +/- 2.7 and 9.9 +/- 1.1/min to 17.3 +/- 0.5 and 11.1 +/- 1.4/min, respectively. The duration of the action potentials in driven cells also increased significantly for several minutes. All these effects were blocked by tetrodotoxin (TTX) (1.6 microM). It was concluded that the positive chronotropic and inotropic effects of nerve stimulation on renal pelvis contractility can be correlated with the changes in the frequency and duration of the action potentials recorded in driven cells.

A role for protein kinase C in bradykinin-mediated activation of renal pelvic sensory receptors

In anesthetized rats, activation of renal pelvic sensory receptors by bradykinin results in an increase in afferent renal nerve activity (ARNA) that is dependent on intact renal prostaglandin synthesis. Since bradykinin is a known activator of the phosphoinositide system, we examined whether the increase in ARNA produced by bradykinin involved activation of protein kinase C (PKC). Renal pelvic perfusion with the phorbol ester 4 beta-phorbol 12,13-dibutyrate (PDBu, 1 microM) increased ARNA (31 +/- 3%, P < 0.01) in rats fed a normal diet but not in rats fed an essential fatty acid-deficient (EFAD) diet. Renal pelvic perfusion with the PKC inhibitors calphostin C (1 microM), staurosporine (20 nM), and H-7 (40 microM) reduced the ARNA responses to bradykinin (20 microM) by 69 +/- 10, 76 +/- 10, and 77 +/- 10%, respectively (all P < 0.01). Pretreatment with PDBu (1 microM), known to cause a feedback inhibition of bradykinin-mediated activation of the phosphoinositide system, reduced the ARNA response to bradykinin by 73 +/- 6% (P < 0.01). Pretreatment with 4 alpha-phorbol 12,13-didecanoate was without effect. These findings suggest that activation of PKC contributes importantly to the activation of renal pelvic sensory receptors by bradykinin, likely via release of arachidonic acid.

Evidence for a reflex provoking contraction of the renal pelvis (with some comments on its clinical implications)

The effect of swallowing a small quantity of water or of solid food (biscuit) on the renogram curve was observed in 177 patients. Swallowing provoked contraction of the renal pelvis in 63% of the kidneys with a pelvicalyceal system which was neither obstructed nor dilated, with expulsion of a substantial fraction of the contents within 30 s. This did not occur in obstructed or denervated kidneys, nor in patients with a high transection of the spinal cord. Evidence is adduced that this contraction is mediated reflexly. This effect may be used diagnostically to distinguish physiological dilatation from obstruction. The implications when performing and interpreting renography are discussed.

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.

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.

Non-adrenergic non-cholinergic excitatory innervation of the guinea-pig isolated renal pelvis: involvement of capsaicin-sensitive primary afferent neurons

Circular muscle strips from the guinea-pig renal pelvis exhibit a spontaneous activity averaging about 50% of maximal contractile response at a frequency of about six contractions/min. This spontaneous activity is tetrodotoxin resistant. Acetylcholine and noradrenaline (one to 100 microM) produce a positive inotropic effect which was abolished or strongly inhibited by atropine and phentolamine, respectively. Electrical field stimulation (five to 10 Hz, 0.5 ms pulse width for 10 s, 60 V, maximal voltage) produces a transient positive inotropic response which is tetrodotoxin-sensitive but unaffected by atropine and phentolamine alone or in combination, as well as by atropine plus guanethidine. Application of capsaicin produced a large positive inotropic response which was not reproduced upon a second application of the drug (desensitization). After in vitro capsaicin desensitization, the response to electrical field stimulation was abolished, indicating its dependence on activation of peripheral endings of sensory nerves. These findings demonstrate the existence of a non-adrenergic non-cholinergic functional innervation of the guinea-pig renal pelvis which is entirely dependent on sensory nerve activation.

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.

Pacemaker activity of the pelvicalyceal border recorded by an intracellular glass microelectrode

Applying intracellular glass microelectrodes to the smooth muscle obtained from the guinea pig pelvicalyceal border, we have succeeded in recording periodic spontaneous action potentials, the so-called slow waves, which are characteristic of a pacemaker. This experiment proved that the pacemaker exists at the pelvicalyceal border. The slow waves originate from the pelvicalyceal border, close to the papilla renalis; they show a biphasic pattern and have the characteristics of a spontaneously excitable cell. The resting potential is 42.3 +/- 1.1 mV, the spontaneous depolarizing potential is 12.1 +/- 0.7 mV, and the depolarizing period is 12/min. The rate of rise of the potential is 22.9 +/- 2.1 mV/s in the first slow depolarization phase, and 50.9 +/- 9.5 mV/s in the following rapid depolarization phase. The rate of decline of the potential is 47.3 +/- 5.4 mV/s in the repolarization phase.

Peptidergic innervation of the normal and obstructed human pyeloureteral junctions

The neuropeptidergic innervation of the normal and obstructed human pyeloureteral junction was investigated using immunohistochemical techniques. A dense innervation of neuropeptide Y (NPY) and vasoactive intestinal polypeptide (VIP) in the intrinsic obstruction type was demonstrated. NPY and VIP formed networks in the muscular layer. NPY was also found in perivascular plexuses and VIP adjacent to the epithelium. Calcitonin gene-related peptide, galanin and substance P nerves were also seen in the muscular layer, although sparsely. It is proposed that NPY and VIP have a role in the pathophysiology of the intrinsic obstruction type of the human pyeloureteral junction. The innervation pattern of the junction with the external type of obstruction was similar to that of the normal pyeloureteral junction.

Calcitonin gene-related peptide (CGRP)-immunoreactive nerve plexuses in the renal pelvis and ureter of rats

The distribution of calcitonin gene-related peptide-immunoreactive nerve fibers in the renal pelvis and ureter was examined by immunohistochemistry using whole-mount preparations and cryostat sections. The patterns of innervation were contrasted between the pelvis and ureter; the immunoreactive nerve fibers in the pelvis ran parallel to the long axis of each of the circular and longitudinal muscle layers, causing a lattice-like appearance of the nerve fibers. In the ureter, the immunoreactive fibers were accumulated in the subepithelial region and the longitudinal muscle. In both the pelvis and ureter, a portion of the nerve fibers of smaller caliber showed a swollen or beaded structure; they were located in the musculature and beneath the epithelium extending for considerable distances. Ligation of the ureter caused a marked decrease in the immunoreactive nerves in the pelvis and the proximal portion of the ureter, suggesting that the axonal flow in the calcitonin gene-related peptide-containing neurons of the ureter runs towards the pelvis.

Contractile behaviour of the human pyelo-ureteral musculature. II. Repetitive electrical stimulation effects

In normal proximal and distal pyeloureteral human strips and in pathological reflux or obstructive segments the influence of repetitive electrical stimulation at frequencies between 0.01 and 200 Hz on their contractile behaviour was studied. Between 0.01 and 1 Hz baseline tone and maximum amplitude of contraction were dependent on stimulation frequencies, but some strips showed an irregular response pattern. At frequencies between 1 and 200 Hz half of the strips showed a typical "on" and "off" contraction (at the beginning and end of the stimulus period respectively) separated by a plateau. We consider the "off" reaction to be a response to an ionic displacement at the end of the stimulus. Spontaneous activity was mostly observed in Tyrode solution and in calix and pyelum. Transmural nerve stimulation did not change the contraction patterns.

[Studies on the in vivo pacemaker potentials of the canine renal pelvis]

In vivo pacemaker potentials of canine renal pelvis were able to be recorded by our new method. Potentials recorded at the pelvicalyceal region of canine renal pelvis in vivo had two phasic slow rising wave form that had duration of 0.2 sec, amplitude of 20 microV and discharge interval of about 5 sec. Furthermore, the discharge interval of ureter EMGs was a integral multiple of that of pacemaker potentials. In diuretic state by intravenous administration of furosemide, pacemaker potentials showed no change in wave form and discharge interval. However, ureter EMGs occurred more frequently to correspond to pacemaker potentials one to one. Noradrenaline and isoproterenol had no action on pacemaker potentials. To the contrary, ureter EMGs were increased by noradrenaline and were decreased by isoproterenol. Acetylcholine had a great variety of action on both pacemaker potentials and ureter EMGs. These results suggest that the pelvicalyceal region as thought to be the pacemaker of ureteral peristalsis is controlled under the influence of parasympathetic nerve system and the ureter is controlled under the influence of both sympathetic and parasympathetic nerve systems.

Conduction velocity in various regions of the renal pelvis and ureter

Conduction velocity of excitation in various regions of the canine pelviureter was studied through the simultaneous recordings of electromyograms at four sites of the canine pelvicalyceal preparation. The pelviureteral system was maintained in the condition which was similar to in vivo situation by infusion of oxygenated Krebs-Ringer solution into the renal pelvis at the average flow rate of living dogs. The conduction velocity was slowest in the proximal region of the pelvis where the pacemaker was located, i.e., about 5.8 mm/sec on an average. The velocity gradually increased in the distal region of the pelvis and the ureter. It was suggested that the conduction velocity of excitation was significantly different in the proximal area of the pelvis, the distal area of the pelvis and the ureter.

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.

Renal chemoreceptors

A study of the renal receptors and types of stimuli which give origin to supraspinal and spinal-mediated autonomic reflexes is presented. Multiunit and single unit recordings from the afferent renal nerves of male Sprague-Dawley rats have revealed two groups of renal chemosensitive receptors (chemoreceptors). These we have called renal R1 and R2 "chemoceptive" receptors. R1 receptors do not have a resting discharge but are activated after 38.7 +/- 3.3 (S.E) sec (n = 40) of complete renal ischemia (occlusion of the renal artery). Other activating stimuli are associated with a marked impairment in renal blood flow (prolonged occlusion of the renal vein and the hypotension of systemic asphyxia or hemorrhage). Their discharge is characterized by trains of impulses which cease abruptly upon re-entry of blood into the kidney. They are not responsive to increases or decreases in renal perfusion pressure or to increases in renal venous or ureteral pressure. In contrast, R2 receptors have a resting discharge and respond vigorously to backflow of normal urine (nondiuretic) into the renal pelvis. The results of the backflow into the pelvis of different test solutions (diuretic and nondiuretic urine, 1 M urea, 1 M mannitol and solutions of NaCl and KCl) indicate that this response is dependent upon the composition of the fluid bathing the renal pelvis rather than the increase in pelvic pressure or pelvic distension. The resting discharge rate is highest in nondiuretic conditions and declines substantially after diuresis is induced by extracellular volume expansion. R2 receptors are also activated by renal ischemia produced by clamping the renal artery. It is concluded that these two groups of afferent sensory units are renal chemosensitive receptors, (chemoreceptors) which respond to the chemical environment of renal interstitium.

Ultrastructure of the urinary tract muscle coat in man. Calices, renal pelvis, pelvi-ureteric junction and ureter

Muscle coat specimens from human calices, renal pelvis, pelvi-ureteric junction, upper, middle and lower ureter segments were examined under an electron microscope. These specimens were taken from 8 patients who had undergone nephroureterectomy: 6 for localized renal carcinoma and 2 for papillary tumor of the pelvis. Two types of smooth muscle cells were observed, "typical" muscle cells and "special" muscle cells. The latter are rich in agranular endoplasmic reticulum, have few myofilaments and are interconnected in numerous, extended, peculiar contact areas. The ratio between these two types of muscle cells differs as also does their innervation between the various segments examined. On the basis of our findings we propose that the "special" muscle cells perform a "pacemaking" function.

Urodynamics of the upper urinary tract

The control of ureteral peristaltic contractions by a pacemaker system is shown in a series of experimental observations on the anesthetized dog. Data are presented to illustrate the influence of pacemaker frequency on ureteral rate and bolus volume during oliguria and transient diuresis. Pacemaker frequency was determined from the pressure wave form of the renal pelvis and peristaltic rate was measured electrophysiologically. The bolus volume associated with each peristaltic contraction was recorded by a drop counter and correlated with pacemaker and ureteral activity. The results show that the pacemaker frequency remains constant over urine flow rates in the range of 0.3 to 15 ml per min. It is also shown that the pacemaker frequency is constant during transient increases in flow rate of more than one order of magnitude. During diuresis, the peristaltic rate changes in quantum steps determined by the fundamental frequency of the pacemaker, and at flow rates greater than 2 ml per min the ureter contracts at the pacemaker rate. Further increases in flow are accommodated by increasing the amount of urine transported by each bolus. The urologic importance of these observations on pacemaker function is discussed in terms of the unicalyceal and multicalyceal upper urinary tract.

In vitro studies on the human renal calices

Smooth muscle preparations taken from the minor calices of human kidneys were investigated by an isolated tissue technique. The existence of alpha-adrenoceptor and muscarinic receptor sites were demonstrated and it was shown that stimulation with the appropriate agonist resulted in an excitatory response. No evidence could be found to support the presence of beta-adrenoceptors in such tissues. The results of transmural electrical stimulation of similar preparations were highly suggestive of an effective innervation of the alpha-adrenoceptors.

Observation on the localization of mechanoreceptors in the kidney and afferent nerve fibres in the renal nerves in the rabbit

1. The distribution and localization of mechanoreceptors in the kidney were studied by recording afferent impulses from the renal nerve bundle or from single nerve fibres in the isoloted kidney preparation in the rabbit. 2. It was observed that mechanoreceptors are distributed in the cranial, central and caudal portions as well as the pelvic portion of the kidney. Diameter range of single nerve fibres from which afferent impulses were recorded was from 2 to 8 mum. 3. Histological studies show that the renal nerve possesses abundant non-myelinated nerve fibres with a relatively small number of myelinated nerve fibres. The myelinated axons had diameters ranging from 0-5 to 13-4 mum and the peak of the unimodal distribution curve was 1-5--2-4 mum.

The Effect of 6-Hydroxydopamine on Nerves in the Rat Upper Urinary Tract

The effect of a single large dose of 6-hydroxydopamine (6-OHDA) on adrenergic nerves in the rat upper urinary tract has been investigated by both light and electron microscopy. Reduction in the intensity of fluorescent catecholamine-containing nerves was seen 1-2 h after drug treatment. At 3-5 h, fluorescing nerves were absent from all preparations. Forty-eight hours after injection fine catecholamine-containing nerves could not be detected, although a few large nerves adjacent to vessels and in the adventitia of the upper urinary tract were associated with increased fluorescence. Using the electron microscope, axons related to smooth muscle were seen to be swollen and contained aggregations of small (50 nm diameter) granulated vesicles and electron-dense material 3-6 h after drug treatment. Other axons contained damaged mitochondria and were devoid of neurofilaments and neurotubules. Normal axons were also seen, some of which contained accumulations of small (50 nm diameter) agranular vesicles and occasional large (100 nm diameter) granulated vesicles. In the submucosa, damaged axons were observed lying close to, or occasionally running between, basal epithelial cells. Axons containing electron-dense clumps of synaptic vesicles were not observed in this situation. Normal axons containing accumulations of small agranular vesicles were identified, some of which were closely related to damaged axon profiles. Forty-eight hours after the drug treatment, some axons related to smooth muscle cells contained accumulations of electron-dense material. All other axons in the wall of the upper urinary tract appeared normal. These results are discussed in relation to the distribution of various types of autonomic nerve in the upper urinary tract.