Renal adrenergic receptors: localization of [125I]prazosin binding sites along the microdissected rat nephron

1992 ◽  
Vol 70 (7) ◽  
pp. 1016-1020 ◽  
Author(s):  
Herbert T. Cohen ◽  
Fumi Takemoto ◽  
Takeo Satoh ◽  
Adrian I. Katz
Keyword(s):  
Binding Sites ◽  
Specific Binding ◽  
Collecting Duct ◽  
Specific Radioactivity ◽  
Dissociation Rate ◽  
Proximal Convoluted Tubule ◽  
Sodium Reabsorption ◽  
Thick Ascending Limb ◽  
Diluting Segment ◽  
High Specific Radioactivity

Norepinephrine stimulates renal tubular sodium reabsorption, probably through an α1-adrenoceptor-mediated mechanism. Although the distribution of α1-adrenoceptors in the kidney has been studied with autoradiography, the precise location of these receptors in isolated nephron segments is unclear. Using a microassay we determined the specific binding of [125I]iodoarylazidoprazosin ([125I]prazosin), a high specific radioactivity analog of the selective α1-antagonist prazosin, to microdissected glomeruli and tubule segments. Specific binding of [125I]prazosin (3 nM) in the proximal convoluted tubule was time- and concentration-dependent, saturable, and reversible. In this segment the apparent KD by association and dissociation rate constants of [125I]prazosin binding was 0.47 nM, and the maximum receptor density was ~ 0.19 fmol/mm, or 720 fmol/mg protein. Binding specificity was verified in competition studies with excess (3 μM) unlabeled prazosin and probes for α2- (yohimbine), β- (propranolol), dopamine1- (SCH23390), and dopamine2- (S-sulpiride) receptors. [125I]Prazosin binding was inhibited significantly only by unlabeled prazosin. Mapping of prazosin binding along the nephron revealed that the highest density was in the proximal convoluted tubule, followed by the proximal straight tubule. Lesser binding was found in the thick ascending limb and in the distal convoluted tubule, whereas in the cortical and outer medullary collecting duct and in glomeruli, binding was not significantly different from zero. These results demonstrate specific prazosin binding sites in the proximal and early distal nephron where direct innervation by monoaminergic nerves is most abundant, and suggest that portions of the nephron beyond the proximal tubule, specifically the diluting segment, may also be under α1-agonist influence.Key words: α1-adrenoceptor, prazosin, isolated tubule, glomerulus, catecholamine.

Insulin Unresponsiveness of Tubular Monovalent Cation Transport during Fructose-Induced Hypertension in Rats

1995 ◽  
Vol 88 (3) ◽  
pp. 293-299 ◽  
Author(s):  
Eric Féraille ◽  
Sophie Marsy ◽  
Catherine Barlet-Bas ◽  
Martine Rousselot ◽  
Lydie Cheval ◽  
...  
Keyword(s):  
Collecting Duct ◽  
Insulin Binding ◽  
Cation Transport ◽  
Proximal Convoluted Tubule ◽  
Sodium Reabsorption ◽  
Thick Ascending Limb ◽  
Cortical Collecting Duct ◽  
Hypertensive Rats ◽  
Medullary Thick Ascending Limb ◽  
Sodium Handling

1. Hyperinsulinaemia is considered to be a pathogenic factor for human and experimental hypertension. Thus, the contribution of the known insulin-stimulated tubular sodium reabsorption to this aetiological process has to be discussed. 2. Rats fed a fructose-enriched diet develop hyperinsulinaemia and hypertension, providing a model for studying the regulation of the tubular sodium handling and its possible relationship to hypertension. For this purpose, the sodium transport capacity of isolated nephron segments from control rats and from rats fed a fructose-enriched diet was investigated by measurement of ouabain-sensitive 86Rb uptake and of the hydrolytic activity of Na,K-ATPase. The number and affinity of insulin receptors were estimated from the specific [125I]insulin binding. 3. In rats fed a fructose-enriched diet, mild hypertension developed during the 14-day fructose diet. There were no differences, along the nephron, in basal 86Rb uptakes and ATPase activities between control rats and fructose-induced hypertensive rats. In control rats, insulin stimulated 86Rb uptake in the proximal convoluted tubule and cortical collecting duct, but exhibited an inhibitory action in the medullary thick ascending limb. In contrast, in fructose-induced hypertensive rats, 86Rb influx remained unresponsive to insulin concentrations ranging from 10−11 to 10−7 mol/l in the proximal convoluted tubule and cortical collecting duct. In the medullary thick ascending limb, the threshold of inhibition was displaced from 10−11 mol/l up to 10−7 mol/l. Insulin binding to the proximal convoluted tubule, medullary thick ascending limb and collecting duct were similar in control rats and in rats fed a fructose-enriched diet. 4. We conclude that hypertension developed in rats fed a fructose-enriched diet regardless of change in renal sodium handling since (1) the basal tubular sodium reabsorption capacity of the nephron remained unchanged and (2) the response of the tubular cation transport to insulin was abolished. These results strongly argue against the participation of insulin-mediated tubular sodium retention in the pathogenesis of hypertension and suggest that insulin-related mechanisms modulate the blood vessel reactivity.

Mineralcorticoid receptors along the nephron: [3H]aldosterone binding in rabbit tubules

1981 ◽  
Vol 241 (6) ◽  
pp. F605-F611 ◽  
Author(s):  
A. Doucet ◽  
A. I. Katz
Keyword(s):  
Binding Sites ◽  
Binding Capacity ◽  
Specific Binding ◽  
Rabbit Kidney ◽  
Scatchard Analysis ◽  
Thick Ascending Limb ◽  
Collecting Tubule ◽  
The Difference ◽  
Collecting Tubules ◽  
Cortical Collecting Tubule

To identify the site of mineralocorticoid action along the nephron, we measured the specific binding of [3H]aldosterone to nephron segments microdissected from aldosterone-deficient rabbits. Specific binding was defined as the difference between binding measured in the absence or in the presence of 2,000-fold excess of unlabeled hormone (in 10(-18) mol X cm tubule length-1 +/- SE). High specific binding capacity was found in the branched collecting tubule (108 +/- 4), the cortical collecting tubule (119 +/- 9), and the outer medullary collecting tubule (115 +/- 16), whereas specific binding was negligible in the proximal convoluted tubule (8 +/- 9), pars recta (2 +/- 6), medullary thick ascending limb (4 +/- 6), cortical thick ascending limb (6 +/- 2), and distal convoluted tubule (6 +/- 6). In cortical collecting tubules, Scatchard analysis of the specific [3H]aldosterone binding indicated a dissociation constant (KD) of 2.2 X 10(-9) M and a maximum number of binding sites of 157 X 10(-18) mol X cm tubule length-1. The steroid specificity was assessed from the competition of various steroids for [3H]aldosterone binding sites. Receptors from the cortical collecting tubule revealed the following sequence of affinities: aldosterone greater than DOCA greater than spironolactone greater than dexamethasone greater than 5 alpha-dihydrotestosterone = progesterone = 17 beta-estradiol, indicating that the binding sites in the collecting tubule are mineralocorticoid receptors. These results demonstrate significant [3H]aldosterone binding to receptors of high affinity and mineralocorticoid specificity only in the collecting tubule and suggest that this nephron segment is the target site of mineralocorticoid action in the rabbit kidney.

Benzodiazepines inhibit transport-related oxygen consumption in thick ascending limb

1988 ◽  
Vol 255 (3) ◽  
pp. C385-C392 ◽  
Author(s):  
F. N. Ziyadeh ◽  
Z. S. Agus
Keyword(s):  
Oxygen Consumption ◽  
Amphotericin B ◽  
Binding Sites ◽  
Cell Function ◽  
Chloride Transport ◽  
Specific Binding ◽  
Rabbit Kidney ◽  
Thick Ascending Limb ◽  
Total Oxygen ◽  
Sodium Uptake

Specific binding sites for benzodiazepines (BZD) have been identified in several nonneuronal tissues including the kidney where they are localized predominantly to the tubular epithelium of the thick ascending limb of Henle's loop (TALH). The physiological function of these nonneuronal (peripheral) BZD-binding sites is undefined, but it has been suggested that they may represent receptors for putative endogenous ligands that may modulate cell function. In the current study, we examined the in vitro effects of diazepam and Ro5-4864, a specific peripheral BZD-receptor agonist, on the oxygen consumption of medullary TALH tubule suspensions of rabbit kidney. Maximal inhibition of total oxygen consumption was achieved at a dose of 5 X 10(-4) M of either agent. On average, diazepam and Ro5-4864 reduced total oxygen consumption by 41 and 44%, respectively. The predominant inhibition was in the ouabain-sensitive component of oxygen consumption, which suggests that BZDs inhibit active sodium-chloride transport in the TALH. To assess whether this inhibition depends on sodium uptake, TALH tubules were pretreated with amphotericin B (2 X 10(-6) M) to enhance sodium uptake and stimulate basal oxygen consumption; subsequent addition of Ro5-4864 (5 X 10(-4) M) still reduced oxygen consumption to a residual value that was not different from that in TALH tubules treated with Ro5-4864 but without pretreatment with amphotericin B. This suggests that BZD inhibition of transport-related oxygen consumption is not caused by diminution of sodium uptake into cells and thus appears to be distinct from the effect of furosemide.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals ANP-induced signaling cascade and its implications in renal pathophysiology

2015 ◽  
Vol 308 (10) ◽  
pp. F1047-F1055 ◽  
Author(s):  
Franziska Theilig ◽  
Qingyu Wu
Keyword(s):  
Natriuretic Peptide ◽  
Transient Receptor Potential ◽  
Salt Water ◽  
Collecting Duct ◽  
Guanosine Monophosphate ◽  
Sodium Reabsorption ◽  
Transient Receptor Potential Vanilloid ◽  
Thick Ascending Limb ◽  
Water Reabsorption ◽  
Glomerular Permeability

The balance between vasoconstrictor/sodium-retaining and vasodilator/natriuretic systems is essential for maintaining body fluid and electrolyte homeostasis. Natriuretic peptides, such as atrial natriuretic peptide (ANP), belong to the vasodilator/natriuretic system. ANP is produced by the conversion of pro-ANP into ANP, which is achieved by a proteolytical cleavage executed by corin. In the kidney, ANP binds to the natriuretic peptide receptor-A (NPR-A) and enhances its guanylyl cyclase activity, thereby increasing intracellular cyclic guanosine monophosphate production to promote natriuretic and renoprotective responses. In the glomerulus, ANP increases glomerular permeability and filtration rate and antagonizes the deleterious effects of the renin-angiotensin-aldosterone system activation. Along the nephron, natriuretic and diuretic actions of ANP are mediated by inhibiting the basolaterally expressed Na+-K+-ATPase, reducing apical sodium, potassium, and protein organic cation transporter in the proximal tubule, and decreasing Na+-K+-2Cl− cotransporter activity and renal concentration efficiency in the thick ascending limb. In the medullary collecting duct, ANP reduces sodium reabsorption by inhibiting the cyclic nucleotide-gated cation channels, the epithelial sodium channel, and the heteromeric channel transient receptor potential-vanilloid 4 and -polycystin 2 and diminishes vasopressin-induced water reabsorption. Long-term ANP treatment may lead to NPR-A desensitization and ANP resistance, resulting in augmented sodium and water reabsorption. In mice, corin deficiency impairs sodium excretion and causes salt-sensitive hypertension. Characteristics of ANP resistance and corin deficiency are also encountered in patients with edema-associated diseases, highlighting the importance of ANP signaling in salt-water balance and renal pathophysiology.

1,25(OH)2D3 binding along the rat nephron: autoradiographic study in isolated tubular segments

1985 ◽  
Vol 248 (2) ◽  
pp. F296-F307 ◽  
Author(s):  
C. Manillier ◽  
N. Farman ◽  
J. P. Bonjour ◽  
J. P. Bonvalet
Keyword(s):  
Binding Sites ◽  
Specific Binding ◽  
Collecting Duct ◽  
Distal Tubule ◽  
Autoradiographic Study ◽  
Cortical Collecting Duct ◽  
Dihydroxyvitamin D3 ◽  
Collecting Tubule ◽  
Autoradiographic Technique

1,25-dihydroxyvitamin D3 [1,25(OH)2D3] binding sites were studied along the nephron of rats. The animals were pretreated with the diphosphonate EHDP at doses that inhibit the endogenous production of 1,25(OH)2D3. A dry film autoradiographic technique was applied to tubular segments isolated by microdissection from kidneys incubated in vitro with various concentrations (0.2-12 nM) of [3H]1,25(OH)2D3 in the presence or absence of an excess unlabeled hormone (X200) in order to determine specific binding. Total, nonspecific, and specific labeling were quantified by silver grain counting over cytoplasmic and nuclear areas. Specific nuclear labeling appeared in the cortical ascending limb and papillary collecting tubule at 1 nM. In the distal tubule and, to a lesser extent, in the cortical collecting tubule a specific nuclear labeling was also present, but only at higher concentrations. No specific nuclear labeling was detected in the proximal tubule. All along the nephron, a significant and nonspecific labeling was observed in the cytoplasm, either alone or superimposed over the specific nuclear labeling. In conclusion 1,25(OH)2D3 specific binding sites appear to be localized mainly in the cortical ascending limb of the loop of Henle, in the distal and cortical collecting duct, and in the papillary collecting duct.

Indomethacin and sodium retention in the rat: role of inhibition of prostaglandin E2 synthesis

1992 ◽  
Vol 83 (3) ◽  
pp. 307-311 ◽  
Author(s):  
Pnina Scherzer ◽  
Hanna Wald ◽  
Dvora Rubinger ◽  
Mordecai M. Popovtzer
Keyword(s):  
Atpase Activity ◽  
Prostaglandin E2 ◽  
Collecting Duct ◽  
Proximal Convoluted Tubule ◽  
Distal Convoluted Tubule ◽  
Thick Ascending Limb ◽  
Cortical Collecting Duct ◽  
Straight Tubule ◽  
Medullary Thick Ascending Limb ◽  
Proximal Straight Tubule

1. To further explore the Na+-retaining effect of indomethacin along the whole length of the nephron, the Na+-K+-ATPase activity of isolated tubules from indomethacin-pretreated rats was compared with that of tubules isolated from intact rats and exposed directly to prostaglandin E2. 2. Indomethacin increased Na+-K+-ATPase activity in the proximal convoluted tubule (+24%, P<0.001 versus control), proximal straight tubule (+75%, P<0.001 versus control), medullary thick ascending limb (+68%, P<0.001 versus control), cortical thick ascending limb (+7%, not significant) and cortical collecting duct (+18%, P<0.025 versus control). In contrast, in the distal convoluted tubule indomethacin decreased Na+-K+-ATPase activity by −42% (P<0.001 versus control). 3. Indomethacin also strongly increased Na+-K+-ATPase activity in the cortical collecting duct of adrenalectomized rats. 4. In isolated tubules from control rats, prostaglandin E2 reduced Na+-K+-ATPase activity in the proximal convoluted tubule (−33%, P<0.05), proximal straight tubule (−60%, P<0.001), medullary thick ascending limb (−43%, P<0.001), cortical thick ascending limb (−25%, P<0.001) and cortical collecting duct (−45%, P<0.001) and in the distal convoluted tubule, prostaglandin E2 increased Na+-K+-ATPase activity (+32%, P<0.05). 5. That these changes in Na+-K+-ATPase activity in indomethacin-pretreated rats and prostaglandin E2-treated controls are similar in magnitude but occur in opposite directions suggests that the response to indomethacin is mediated by inhibition of prostaglandin E2 synthesis in the nephron. In the cortical collecting duct the effect of indomethacin is aldosterone-independent.

Connexin 37 is localized in renal epithelia and responds to changes in dietary salt intake

2010 ◽  
Vol 298 (1) ◽  
pp. F216-F223 ◽  
Author(s):  
Adelina Stoessel ◽  
Nina Himmerkus ◽  
Markus Bleich ◽  
Sebastian Bachmann ◽  
Franziska Theilig
Keyword(s):  
Gap Junctions ◽  
Epithelial Transport ◽  
Salt Intake ◽  
Collecting Duct ◽  
Mrna Level ◽  
High Salt ◽  
Sodium Reabsorption ◽  
Thick Ascending Limb ◽  
Renal Epithelia ◽  
Basolateral Side

Connexins are the main components of gap junction channels, which are important for intercellular communication. In the kidney, several members of the connexin (Cx) family have been identified. Renal vascular expression and hemodynamic impacts have so far been shown for Cx37, Cx40, and Cx43. Additionally, Cx30, Cx30.3, and Cx43 have been identified to be part of tubular epithelial gap junctions and/or hemichannels. However, the localization and role of other Cx family members in renal epithelial structures remain undetermined. We aimed to localize Cx37 in the kidney to obtain information on its epithelial expression and potential functions. Immunohistochemistry in rodent kidney showed characteristic punctate patterns in the vasculature and along the nephron. Strong basolateral expression was found in the thick ascending limb and distal convoluted tubule. Weaker abundances were found in the proximal tubule and the collecting duct also at the basolateral side. In situ hybridization and real-time PCR of isolated nephron segments confirmed this distribution at the mRNA level. Ultrastructurally, Cx37 immunostaining was confined to basolateral cell interdigitations and infoldings. As a functional approach, rats were fed low- or high-salt diets. Compared with control and high-salt diets, rats treated with low-salt diet showed significantly increased Cx37 mRNA and protein levels. This may be indicative of an adaptive tubular response to changes in sodium reabsorption. In summary, renal epithelia express Cx37 in their basolateral membranes. Here, the formation of Cx37 gap junctions may be involved in cellular communication and adjustments of vectorial epithelial transport.

Substrate utilization by the distal nephron in dogs with chronic metabolic acidosis: studies with ethacrynic acid

1985 ◽  
Vol 63 (12) ◽  
pp. 1565-1569 ◽  
Author(s):  
Mitchell L. Halperin ◽  
Ching B. Chen
Keyword(s):  
Metabolic Acidosis ◽  
Ethacrynic Acid ◽  
Proximal Convoluted Tubule ◽  
Sodium Reabsorption ◽  
Thick Ascending Limb ◽  
Distal Nephron ◽  
Chronic Metabolic Acidosis ◽  
Fractional Excretion Of Sodium ◽  
Renal Oxygen Consumption ◽  
Dog Kidney

Glutamine and lactate oxidations provide the bulk of ATP required for sodium reabsorption in the dog kidney during chronic metabolic acidosis. Indirect evidence has suggested that glutamine is oxidized in the proximal convoluted tubule; if this is true, lactate should be the major fuel of the more distal nephron sites. The purpose of these experiments was to determine which substrates were metabolized by the acidotic dog kidney when a significant proportion of sodium chloride reabsorption was inhibited in the thick ascending limb of the loop of Henle. Ethacrynic acid, a loop diuretic, caused the fractional excretion of sodium to increase from 1 to 34%. The glomerular filtration rate declined somewhat, but there was no significant change in the renal blood flow rate. Renal oxygen consumption declined in conjunction with the natriuresis. However, when the data were examined at a constant filtered load of sodium (a constant rate of ATP turnover), there was no reduction in glutamine uptake or glutamine conversion to ATP in the presence of this natriuretic agent. The major change observed concerned lactate metabolism, in the presence of ethacrynic acid, there was no longer a significant rate of lactate extraction. These data are best explained by assuming that glutamine is the fuel of the proximal convoluted tubule of the acidotic dog kidney, whereas lactate oxidation occurs principally in the nephron sites where sodium reabsorption was inhibited by ethacrynic acid.

NEM-sensitive ATPase activity in rat nephron: effect of metabolic acidosis and alkalosis

1990 ◽  
Vol 258 (2) ◽  
pp. F297-F304 ◽  
Author(s):  
S. Sabatini ◽  
M. E. Laski ◽  
N. A. Kurtzman
Keyword(s):  
Enzyme Activity ◽  
Metabolic Acidosis ◽  
Atpase Activity ◽  
Collecting Duct ◽  
Proximal Convoluted Tubule ◽  
Thick Ascending Limb ◽  
Cortical Collecting Duct ◽  
Chronic Metabolic Acidosis ◽  
Collecting Tubule ◽  
Cortical Collecting Tubule

The present study was designed to quantitate the amount and to map the localization of N-ethylmaleimide (NEM)-sensitive adenosinetriphosphatase (ATPase) activity in microdissected segments of the rat nephron. After complete nephron mapping the effect of chronic metabolic acidosis and alkalosis on enzyme activity was determined. In control animals the highest enzyme activity was found in the early proximal convoluted tubule of juxtamedullary nephrons; superficial early proximal tubule as well as medullary and cortical thick ascending limbs and collecting ducts also contained substantial activity. Enzyme activity in the papillary collecting duct before entry into the ducts of Bellini was 329 +/- 93 pmol.mm-1.h-1 (n = 8); after entry, however, enzyme activity was approximately one-fourth that value (60 +/- 9 pmol.mm-1.h-1, n = 8, P less than 0.01). No NEM-sensitive ATPase activity was found in the thin limbs of the loop of Henle. Enzyme activity increased in both the medullary and cortical thick ascending limbs as well as in the cortical collecting tubule in response to NH4Cl-induced chronic metabolic acidosis; in the cortical collecting duct, metabolic acidosis increased maximum activity (Vmax) but did not change Michaelis-Menten constant (Km). In the proximal convoluted tubule, enzyme activity decreased with metabolic acidosis. Bicarbonate loading had no effect on enzyme activity except in the most distal portion of the collecting duct where it was stimulated. These results show that NEM-sensitive ATPase activity exists throughout much of the rat nephron. These data suggest that both the cortical collecting tubule and thick ascending limb are regulatory sites of distal urinary acidification during acid loading.

Aldosterone binding along the rabbit nephron: an autoradiographic study on isolated tubules

1981 ◽  
Vol 240 (3) ◽  
pp. F172-F179 ◽  
Author(s):  
A. Vandewalle ◽  
N. Farman ◽  
P. Bencsath ◽  
J. P. Bonvalet
Keyword(s):  
Binding Sites ◽  
Specific Binding ◽  
Autoradiographic Study ◽  
Rabbit Kidney ◽  
Thick Ascending Limb ◽  
Collecting Ducts ◽  
Sites Of Action ◽  
Convoluted Tubules ◽  
Silver Grains ◽  
Dry Film

The sites of action of aldosterone (A) along the tubule of rabbit kidney were studied by autoradiographic localization of mineralocorticoid-binding sites on microdissected tubular segments. Kidney pyramids were incubated at 30 degrees C for 1 h in a collagenase solution with [3H]aldosterone at a concentration of 1.5 X 10(-9) M with and without an excess unlabeled A. Tubular segments were then microdissected and transferred onto dry film; fixation and staining were done only after exposure of the film 4 mo later in order to avoid diffusion. Specific nuclear labeling was 19.0 +/- 1.3 silver grains/100 micrometers2 in distal convoluted tubules (n = 28) and 21.0 +/- 1.8 in cortical collecting ducts (n = 18). No difference between these two structures was observed (P greater than 0.1, paired t test, n = 15). No specific binding was found in the proximal tubule (0.5 +/- 0.4, n = 17). In the thick ascending limb of Henle's loop, the labeling was low (3.9 +/- 0.9, n = 16). We conclude that, in the rabbit kidney, nuclear mineralocorticoid-binding sites, presumably receptors, are present in the distal and cortical collecting tubule.

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