Vasoactive intestinal peptide-immunoreactive nerves in the rat kidney

Sympathetic innervation of the mouse kidney and liver arising from prevertebral ganglia

The sympathetic nervous system (SNS) plays a crucial role in the regulation of renal and hepatic functions. Although sympathetic nerves to the kidney and liver have been identified in many species, specific details are lacking in the mouse. In the absence of detailed information of sympathetic prevertebral innervation of specific organs, selective manipulation of a specific function will remain challenging. Despite providing major postganglionic inputs to abdominal organs, limited data are available about the mouse celiac-superior mesenteric complex. We used tyrosine hydroxylase (TH) and dopamine β-hydroxylase (DbH) reporter mice to visualize abdominal prevertebral ganglia. We found that both the TH and DbH reporter mice are useful models for identification of ganglia and nerve bundles. We further tested if the celiac-superior mesenteric complex provides differential inputs to the mouse kidney and liver. The retrograde viral tracer, pseudorabies virus (PRV)-152 was injected into the cortex of the left kidney or the main lobe of the liver to identify kidney-projecting and liver-projecting neurons in the celiac-superior mesenteric complex. iDISCO immunostaining and tissue clearing were used to visualize unprecedented anatomical detail of kidney-related and liver-related postganglionic neurons in the celiac-superior mesenteric complex and aorticorenal and suprarenal ganglia compared with TH-positive neurons. Kidney-projecting neurons were restricted to the suprarenal and aorticorenal ganglia, whereas only sparse labeling was observed in the celiac-superior mesenteric complex. In contrast, liver-projecting postganglionic neurons were observed in the celiac-superior mesenteric complex and aorticorenal and suprarenal ganglia, suggesting spatial separation between the sympathetic innervation of the mouse kidney and liver.

Selective vs. Global Renal Denervation: a Case for Less Is More

PURPOSE OF REVIEW

Review the renal nerve anatomy and physiology basics and explore the concept of global vs. selective renal denervation (RDN) to uncover some of the fundamental limitations of non-targeted renal nerve ablation and the potential superiority of selective RDN.

RECENT FINDINGS

Recent trials testing the efficacy of RDN showed mixed results. Initial investigations targeted global RDN as a therapeutic goal. The repeat observation of heterogeneous response to RDN including non-responders with lack of a BP reduction, or even more unsettling, BP elevations after RDN has raised concern for the detrimental effects of unselective global RDN. Subsequent studies have suggested the presence of a heterogeneous fiber population and the potential utility of renal nerve stimulation to identify sympatho-stimulatory fibers or "hot spots." The recognition that RDN can produce heterogeneous afferent sympathetic effects both change therapeutic goals and revitalize the potential of therapeutic RDN to provide significant clinical benefits. Renal nerve stimulation has emerged as potential tool to identify sympatho-stimulatory fibers, avoid sympatho-inhibitory fibers, and thus guide selective RDN.

Contribution of K(+) channels to endothelium-derived hypolarization-induced renal vasodilation in rats in vivo and in vitro

We investigated the mechanisms behind the endothelial-derived hyperpolarization (EDH)-induced renal vasodilation in vivo and in vitro in rats. We assessed the role of Ca(2+)-activated K(+) channels and whether K(+) released from the endothelial cells activates inward rectifier K(+) (Kir) channels and/or the Na(+)/K(+)-ATPase. Also, involvement of renal myoendothelial gap junctions was evaluated in vitro. Isometric tension in rat renal interlobar arteries was measured using a wire myograph. Renal blood flow was measured in isoflurane anesthetized rats. The EDH response was defined as the ACh-induced vasodilation assessed after inhibition of nitric oxide synthase and cyclooxygenase using L-NAME and indomethacin, respectively. After inhibition of small conductance Ca(2+)-activated K(+) channels (SKCa) and intermediate conductance Ca(2+)-activated K(+) channels (IKCa) (by apamin and TRAM-34, respectively), the EDH response in vitro was strongly attenuated whereas the EDH response in vivo was not significantly reduced. Inhibition of Kir channels and Na(+)/K(+)-ATPases (by ouabain and Ba(2+), respectively) significantly attenuated renal vasorelaxation in vitro but did not affect the response in vivo. Inhibition of gap junctions in vitro using carbenoxolone or 18α-glycyrrhetinic acid significantly reduced the endothelial-derived hyperpolarization-induced vasorelaxation. We conclude that SKCa and IKCa channels are important for EDH-induced renal vasorelaxation in vitro. Activation of Kir channels and Na(+)/K(+)-ATPases plays a significant role in the renal vascular EDH response in vitro but not in vivo. The renal EDH response in vivo is complex and may consist of several overlapping mechanisms some of which remain obscure.

Transitory noradrenergic and peptidergic nerves in the cat kidney

Indirect immunohistochemical methods were used to visualize nerves immunoreactive for tyrosine hydroxylase (TH), dopamine beta hydroxylase (DBH), neuropeptide Y, (NPY) and calcitonin gene-related peptide (CGRP) in sections of the kidneys of cats of different ages. Nerve terminals immunoreactive for TH, DBH and NPY innervated interlobar veins and the renal arterial tree including medullary vascular bundles of cats of each age studied. Most nerve terminals immunoreactive for CGRP innervated interlobar arteries. In kidneys of cats 2 to 10 weeks old, TH- and DBH-immunoreactive axons formed elaborate plexuses that were distributed throughout much of the outer two thirds of the inner medulla. Inner medullary NPY-immunoreactive nerve terminals formed sparse plexuses by comparison, thus suggesting a large population of TH-immunoreactive nerve terminals not immunoreactive for NPY. Plexuses immunoreactive for CGRP also innervated the inner medullae of young cats. Some inner medullary axons appeared degenerate in 8 and 10 week old cats, and no inner medullary nerve terminal plexuses were visualized in 12 week old or adult cats. Cell death or paring of axons resulting from mechanisms intrinsic to the neuronal population or from a change in trophic factors secreted or expressed by cells in the medulla may effect the loss of inner medullary nerve terminals in the kidneys of young cats.

Renal sodium excretion following systemic infusion of vasoactive intestinal peptide in the rat

1. The aim of this clearance study was to examine the renal effects of systemic infusion of vasoactive intestinal peptide (VIP) in the intact rat. 2. Mean arterial blood pressure (MAP), plasma electrolytes and haematocrit, glomerular filtration rate (GFR), and urinary sodium and potassium excretion were measured in a baseline period and following VIP infusion (0.1-1.2 nmol/h per 200 g), as well as during a time control study. 3. During infusion of low doses of VIP (0.1 and 0.4 nmol/h per 200 g), a small increase in fractional and absolute excretion of sodium occurred but this did not differ from that occurring in the time control group. In the high dose VIP group (1.2 nmol/h per 200 g), significant falls occurred in MAP and GFR, and absolute sodium excretion fell (though not significantly) from its baseline level. 4. These findings suggest that systemic VIP has no net natriuretic effect in the rat, but produces haemodynamic changes associated with reduced sodium excretion at high doses. This study does not exclude the possibility of direct effects on tubular sodium transport of VIP released from renal nerves.

Vasoactive intestinal peptide binding sites and fibers in the brain of the pigeon Columba livia: an autoradiographic and immunohistochemical study

The distribution of vasoactive intestinal peptide (VIP) binding sites in the pigeon brain was examined by in vitro autoradiography on slide-mounted sections. A fully characterized monoiodinated form of VIP, which maintains the biological activity of the native peptide, was used throughout this study. The highest densities of binding sites were observed in the hyperstriatum dorsale, archistriatum, auditory field L of neostriatum, area corticoidea dorsolateralis and temporo-parieto-occipitalis, area parahippocampalis, tectum opticum, nucleus dorsomedialis anterior thalami, and in the periventricular area of the hypothalamus. Lower densities of specific binding occurred in the neostriatum, hyperstriatum ventrale and nucleus septi lateralis, dorsolateral area of the thalamus, and lateral and posteromedial hypothalamus. Very low to background levels of VIP binding were detected in the ectostriatum, paleostriatum primitivum, paleostriatum augmentatum, lobus parolfactorius, nucleus accumbens, most of the brainstem, and the cerebellum. The distribution of VIP-containing fibers and terminals was examined by indirect immunofluorescence using a polyclonal antibody against porcine VIP. Fibers and terminals were observed in the area corticoidea dorsolateralis, area parahippocampalis, hippocampus, hyperstriatum accessorium, hyperstriatum dorsale, archistriatum, tuberculum olfactorium, nuclei dorsolateralis and dorsomedialis of the thalamus, and throughout the hypothalamus and the median eminence. Long projecting fibers were visualized in the tractus septohippocampalis. In the brainstem VIP immunoreactive fibers and terminals were observed mainly in the substantia grisea centralis, fasciculus longitudinalis medialis, lemniscus lateralis, and in the area surrounding the nuclei of the 7th, 9th, and 10th cranial nerves. The correlation between the distribution of VIP binding sites and immunoreactive fibers and terminals was assessed in a restricted number of regions. A qualitatively good matching was found in the area corticoidea dorsolateralis, hyperstriatum dorsale, hyperstriatum accessorium, nucleus septi lateralis, nuclei dorsomedialis and dorsolateralis thalami, and in some hypothalamic areas. A striking mismatch occurred in the hyperstriatum ventrale, neostriatum, tectum opticum (high to moderate density of binding sites but only few immunoreactive profiles), and in the tuberculum olfactorium, median eminence, and spinal cord (lower density of binding sites but abundant immunoreactive profiles). The paleostriatum, lobus parolfactorius, and ectostriatum were virtually devoid of both binding sites and immunoreactive profiles. The results are discussed in relation to the known actions of VIP in the rodent and avian brain and are compared with previous observations on the distribution of VIP binding sites in the central nervous system of other vertebrates.

Vasoactive intestinal polypeptide nerve fibers in human and monkey (Macaca fascicularis and Macaca mulatta) kidneys

Nerve fibers immunoreactive for vasoactive intestinal polypeptide (VIP) were demonstrated for the first time by the indirect immunofluorescence technique in human and monkey kidneys. VIP-immunoreactive nerve fibers showing varicosities were observed in the adventitia of arcuate arteries and their branches. The density of VIP-immunoreactive nerve fibers decreased from the juxtamedullary region to the cortex. Occasionally a VIP-immunoreactive varicose nerve fiber was observed near the vascular pole of a glomerulus, but no direct innervation of afferent or efferent arterioles in either monkey or human kidney was found. The distribution of VIP-immunoreactive nerve fibers in the monkey and human kidneys was similar to that reported in other species, with less density. The functional role of VIP in the innervation of the kidney is not known, but various suggestions have been made regarding the possible involvement of VIP on vasodilation of selective intrarenal blood vessels, renin secretion, and/or effects on tubules. While none of these questions were established at this time they would appear to be logical areas for further study.

Transitory inner medullary nerve terminals in the cat kidney

An indirect immunohistochemical method was used to visualize nerves immunoreactive for tyrosine hydroxylase (THI) and dopamine-beta-hydroxylase (DBHI) in kidney sections of cats 6 weeks and 2 and 3 months of age. THI and DBHI nerve terminals innervate the renal pelvis, interlobar veins and arterial tree including medullary vascular bundles of cats of each age studied. In kidneys of 6-week-old cats, THI and DBHI axons form elaborate plexuses that are distributed throughout much of the inner medulla, whereas some medullary axons appear to degenerate at 2 months and no inner medullary plexuses were visualized in 3-month-old cats. Transitory inner medullary nerves in the cat kidney may influence cellular development and play a role in salt and water balance.

Age-dependent changes of the sympathetic innervation of the rat kidney

The influence of aging on the sympathetic innervation of the kidney was studied in 3- (considered to be young), 12- (considered to be adult) and 24- (considered to be old) month-old male Sprague-Dawley rats by means of high pressure liquid chromatography with electrochemical detection, catecholamine histofluorescence and acetylcholinesterase (AChE) histochemistry. Body and kidney weights were significantly increased in adult in comparison with young rats. No further increase of either body or kidney weight was appreciated in old rats. Noradrenaline levels were increased by about 48% in adult rats and were decreased in old rats (by approx. 22% vs. young and 60% vs. adult). The density of perivascular noradrenergic fibres was significantly increased in adult rats and decreased in old animals. The percentage of kidney glomeruli supplied by AChE-positive nerve fibres is also remarkably increased in 12-month old rats and decreased in 24-month-old rats. The present data indicate that there is a striking increase in the expression of sympathetic innervation of rat kidney at 12 months of age followed by a significant decrease in the expression of innervation in old age. These changes are discussed in relation to the age-dependent impairment of renal function.

Vasoactive intestinal peptide stimulation of human renal adenylate cyclase in vitro

1. A direct action of vasoactive intestinal peptide (VIP) upon human kidney was sought by measurement of renal adenylate cyclase in tissue homogenates and plasma membranes isolated from tissue samples excised for therapeutic reasons. 2. VIP (1 microM) produced a mean stimulation of adenylate cyclase activity of 3.5-fold compared to basal values in cortical plasma membranes; comparative stimulations of 2.8-fold and 27.3-fold were obtained with 1 microM-glucagon and 1 microM-h(1-34) parathyroid hormone respectively. 3. Half-maximal stimulation of human renal cortical plasma membrane adenylate cyclase was observed with a mean value of 35 nM-VIP. 4. The stimulation of renal adenylate cyclase by VIP appeared to be specific because stimulation by glucagon was additive to that obtained with VIP, and the VIP receptor antagonist (4 Cl-D-Phe6, Leu17)-VIP inhibited the VIP-dependent stimulation of adenylate cyclase activity.

Localisation and characterisation of functional vasoactive intestinal peptide receptors in feline kidney

Specific 125I-labelled vasoactive intestinal peptide (VIP) binding was determined in feline renal cortical and medullary plasma membranes. For the cortex, Scatchard analysis of the data resulted in a curvilinear plot with a high-affinity site K0.5 of 8.4 +/- 2.6 nmol l-1 (SE, n = 6) and a second low-affinity site K0.5 204 +/- 16 nmol l-1 with binding site concentrations (Bmax) of 385 +/- 44.5 and 2710 +/- 181.3 fmol mg protein-1 respectively. Conversely a similar analysis of the results obtained for outer medullary membranes gave a single site with a K0.5 of 1.2 +/- 0.2 nmol l-1 (SE, n = 4) and Bmax of 157.8 +/- 24.7 fmol mg-1. Inner medullary membrane binding data. Gave a single site of lower affinity (K0.5 = 62.5 +/- 21.6 nmol l-1; n = 3). Structurally related peptides, glucagon and secretin, were ineffective (up to 1 mumol l-1) in displacing VIP from specific sites in both cortex and medulla. Porcine PHI 1-27 (a peptide having N-terminal histidine and C-terminal isoleucine) and a VIP antagonist [4-Cl-D-Phe6Leu17]VIP both displaced 125I-VIP from cortical and medullary membrane binding sites with IC50 values of 43.0 nmol l-1 and 1.3 mumol l-1 (cortex) and 132.0 nmol l-1 and 1.5 mumol l-1 (medulla) respectively. The localisation of specific VIP binding sites in feline kidney was investigated further by in vitro autoradiography.(ABSTRACT TRUNCATED AT 250 WORDS)

Catecholamine-containing, dopamine-beta-hydroxylase-immunoreactive perivascular nerve specializations in the rat kidney

Fluorescence histochemical visualization of catecholamines and immunolabeling of dopamine beta hydroxylase (DBH) were employed to study noradrenergic nerve terminals and perivascular nerve specializations in the rat kidney. Plexuses of catecholamine-containing and dopamine-beta-hydroxylase-immunoreactive nerves innervate the intrarenal arterial tree and larger intrarenal veins. Some perivascular nerve bundles have specialized segments composed of clusters of axonal enlargements that are immunoreactive for DBH and fluoresce intensely in ultraviolet light after fixation in a solution of formaldehyde and glutaraldehyde or treatment with glyoxylic acid. No fluorescent neural structures were found in denervated rat kidney sections treated with glyoxylic acid. Many such structures are associated with arteriolar branches of interlobar, arcuate, and interlobular arteries and are composed, in part, of axonal enlargements that contain mitochondria, microtubules, and one or more clusters of synaptic vesicles. These perivascular nerve specializations may be sites of axoaxonal interactions between noradrenergic axons or between these axons and other types of autonomic or sensory axons. The synaptic vesicles evidently store large amounts of catecholamine, but there is no evidence whether it is released into the surrounding tissue. These structures may be involved in changes in intrarenal innervation patterns which may occur as the rat ages. Regardless of the autonomic or sensory nature of intrarenal neural structures, close association of most such structures with arterioles suggests some neurovascular interaction.

Vasoactive intestinal peptide stimulation of renal adenylate cyclase and antagonism by (4Cl-D-Phe6Leu17)VIP

The effect of vasoactive intestinal peptide (VIP) and related peptides [glucagon, secretin, PHI 1-27 (peptide with N-terminal histidine and C-terminal isoleucine)] on renal adenylate cyclase (AC) has been determined in several species. The largest stimulation (4.1 +/- 0.5-fold basal) of AC by 1 mumol.l-1 VIP was observed in feline cortical plasma membranes. In rabbit and guinea-pig, VIP increased AC activity 1.5 +/- 0.3- and 1.8 +/- 0.3-fold respectively but glucagon had no such action. Conversely in the rat glucagon stimulated AC some 3-fold over basal activity whereas VIP had little effect. In dog, cat and mouse both peptides were effective in increasing AC activity. For cat, half-maximal stimulation of cortical plasma membrane AC by VIP was seen at 27.0 +/- 9.0 nmol.l-1 (SE N = 9 animals). VIP also increased AC activity in both outer (red) and inner (white) medulla. In feline cortical membranes VIP and PTH (parathyroid hormone) when added in combination were fully additive. However for VIP and glucagon in combination there was no cumulative increase in AC activity, indeed the resultant activity was less than that attained by VIP alone. The VIP analogue (4Cl-D-Phe6Leu17)VIP at 10 mumol.l-1 produced a right shift in the VIP-dose response curve and increased the EC50 from 17.2 +/- 5.8 nmol.l-1 to 132.0 +/- 22.2 nmol..-1 VIP (SE N = 4). There was no reduction in the maximum response elicited by VIP consistent with a competitive type of antagonism by this analogue. PHI-stimulated AC was also reduced by (4Cl-D-Phe6Leu17)VIP resulting in a similar right shift in the dose response curve.(ABSTRACT TRUNCATED AT 250 WORDS)

Identification of noradrenergic nerve terminals immunoreactive for neuropeptide Y and vasoactive intestinal peptide in the rat kidney

Cryostat- and vibratome-cut sections of rat kidneys were singly or doubly labeled to visualize immunoreactive tyrosine hydroxylase (THI), dopamine beta-hydroxylase (DBHI), vasoactive intestinal peptide (VIPI), and neuropeptide Y (NPYI). Rats were perfusion fixed with 2-4% paraformaldehyde with or without 0.15% picric acid and rinsed in buffer for 18-48 hr. Single antigens were labeled with horseradish peroxidase in vibratome sections, whereas cryostat sections were used to label one antigen with peroxidase and another with a fluorophore in the same tissue section. A dense plexus of DBHI noradrenergic nerves innervates the renal arterial tree, and such nerves innervate the interlobar veins and renal calyx as well. Immunoreactive NPY is colocalized in most of these nerves, but some intrarenal noradrenergic nerves do not contain NPY but do contain VIP immunoreactivity. The distribution of NPYI nerves resembles that of DBHI nerves, whereas most perivascular noradrenergic nerves immunoreactive for VIP innervate selected arcuate and interlobular arteries. A small population of nonadrenergic, VIPI nerves innervates the renal calyx.

Regulatory peptides in the mammalian urogenital system

By immunocytochemistry a number of the gut/brain peptides have been demonstrated in nerve fibers of the mammalian urogenital tract. These peptides are localized to large vesicles in nerve terminals of afferent fibers or efferent nerves innervating blood vessels, non-vascular smooth muscle, lining epithelium and glands. There is evidence that some neuropeptides (VIP, NPY) participate in the local non-cholinergic, non-adrenergic nervous control of smooth muscle activity and blood flow, while other peptides (substance P, CGRP) seem to be sensory transmitters. It is likely that impaired function of the peptidergic nerves is involved in sexual dysfunction such as male impotence.

High- and low-affinity binding sites for vasoactive intestinal peptide (VIP) in the rat kidney revealed by light microscopic autoradiography

The distribution of VIP binding sites in rat kidney and adrenal gland has been examined by light microscopic autoradiography. A fully characterized mono-iodinated molecular form of VIP (M-125-I-VIP) which maintains the biological activity of the native peptide, was used for this study. Two types of VIP binding sites, with high and low affinity, have been identified. High affinity sites are associated with (i) glomerular structures in the cortex, (ii) the inner stripe of the outer medulla, possibly corresponding to Henle's loops and distal tubules, (iii) radiated structures in the inner zone of the medulla, likely to represent labeling of collecting ducts and/or vascular bundles and (iv) the adrenal cortex. Autoradiographic grains associated with low affinity sites are present diffusely throughout the renal cortex, possibly corresponding to labeling of tubular and/or vascular structures, and throughout the adrenal gland. These observations further delineate a role of VIP in renal and neuroendocrine function.

Distribution of vasoactive intestinal peptide-sensitive adenylate cyclase activity along the rabbit nephron

The effect of vasoactive intestinal peptide (VIP) upon adenylate cyclase (AC) activity has been determined in defined microdissected renal tubules isolated from collagenase-treated rabbit kidneys. In the presence of 10 microM GTP, 1 microM VIP gave marked stimulations of AC over basal values in the bright portion of the distal convoluted tubule (DCTb) (10.1-fold), and in the collecting tubule isolated from the inner stripe of the outer medulla (OMCTi, 7.8-fold). Less pronounced effects of VIP were found in the medullary collecting tubule isolated from the outer stripe (2.5-fold) and in the granular portion of the distal convoluted tubule (2.0-fold). VIP stimulation of AC activity in these segments amounted to 25 to 40% of the effect elicited by other agonists (arginine vasopressin, calcitonin or parathyroid hormone) in their respective target segments. A low response to VIP was observed in the cortical thick ascending limb (1.8-fold) which represented less than 5% of the calcitonin-stimulated AC activity. In the thin descending limb VIP produced a slight and variable stimulation of AC. VIP was without effect upon AC in the convoluted and straight portions of the proximal tubule, the medullary thick ascending limb and the cortical collecting tubule. Half-maximal stimulation of AC by VIP was observed at 26 +/- 10 nM (n = 3) in OMCTi and at 19 nM (n = 2) in DCTb. Related peptides glucagon, secretin and PHI gave lower stimulations of AC compared to VIP in OMCTi. Conversely for rat OMCTi, under identical conditions, glucagon was much more effective than VIP.

Substance P-immunoreactive nerves in the rat kidney

An indirect immunohistochemical method in which an avidin-biotinylated horseradish peroxidase complex is bound to the secondary antibody was used to visualize substance P-immunoreactive (SPI) nerves in the rat kidney. Rats were perfused with 2% paraformaldehyde + 0.15% picric acid in 0.1 M phosphate buffer, then transferred to the buffer. After 24-48 h, the kidneys were sectioned with a Vibratome at 200 or 300 micron and incubated in the primary antiserum for 18 h at room temperature. A dense plexus of SPI nerves innervates the rat renal calyx. A small proportion of intrarenal SPI axons innervates interlobular arteries and afferent arterioles, but most perivascular SPI axons terminate on interlobar and arcuate arteries. The densest plexuses are located on segments of interlobar arteries near the hilus of the kidney. Some of these axons probably are nociceptive; others may be chemo- or baroreceptive.