Macula densa basolateral ATP release is regulated by luminal [NaCl] and dietary salt intake

2004 ◽  
Vol 286 (6) ◽  
pp. F1054-F1058 ◽  
Author(s):  
Peter Komlosi ◽  
Janos Peti-Peterdi ◽  
Amanda L. Fuson ◽  
Attila Fintha ◽  
Laszlo Rosivall ◽  
...  
Keyword(s):  
Salt Intake ◽  
Mesangial Cells ◽  
Basolateral Membrane ◽  
Atp Release ◽  
Macula Densa ◽  
Tubuloglomerular Feedback ◽  
Thick Ascending Limb ◽  
Dietary Salt ◽  
Dietary Salt Intake ◽  
High Salt Intake

One component of the macula densa (MD) tubuloglomerular feedback (TGF) signaling pathway may involve basolateral release of ATP through a maxi-anion channel. Release of ATP has previously been studied during a maximal luminal NaCl concentration ([NaCl]L) stimulus (20–150 mmol/l). Whether MD ATP release occurs during changes in [NaCl]L within the physiological range (20–60 mmol/l) has not been examined. Also, because TGF is known to be enhanced by low dietary salt intake, we examined the pattern of MD ATP release from salt-restricted rabbits. Fluorescence microscopy, with fura 2-loaded cultured mouse mesangial cells as biosensors, was used to assess ATP release from the isolated, perfused thick ascending limb containing the MD segment. The mesangial biosensor cells, which contain purinergic receptors and elevate intracellular Ca2+ concentration ([Ca2+]i) on ATP binding, were placed adjacent to the MD basolateral membrane. Elevations in [NaCl]L between 0 and 80 mmol/l, in 20-mmol/l increments, caused stepwise increases in [Ca2+]i, with the highest increase at [NaCl]L of ∼60 mmol/l. Luminal furosemide at 10−4 mol/l blocked ATP release, which suggests that the efflux of ATP required MD Na-2Cl-K cotransport. A low-salt diet for 1 wk increased the magnitude of [NaCl]L-dependent elevations in biosensor [Ca2+]i by twofold, whereas high-salt intake had no effect. In summary, ATP release occurs over the same range of [NaCl]L (20–60 mmol/l) previously reported for TGF responses, and, similar to TGF, ATP release was enhanced by dietary salt restriction. Thus these two findings are consistent with the role of MD ATP release as a signaling component of the TGF pathway.

scholarly journals Salt-sensitive splice variant of nNOS expressed in the macula densa cells

2010 ◽  
Vol 298 (6) ◽  
pp. F1465-F1471 ◽  
Author(s):  
Deyin Lu ◽  
Yiling Fu ◽  
Arnaldo Lopez-Ruiz ◽  
Rui Zhang ◽  
Ramiro Juncos ◽  
...  
Keyword(s):  
Salt Intake ◽  
Splice Variants ◽  
Macula Densa ◽  
High Salt ◽  
Tubuloglomerular Feedback ◽  
No Production ◽  
Thick Ascending Limb ◽  
High Salt Diet ◽  
Salt Diet ◽  
High Salt Intake

Neuronal nitric oxide synthase (nNOS), which is abundantly expressed in the macula densa cells, attenuates tubuloglomerular feedback (TGF). We hypothesize that splice variants of nNOS are expressed in the macula densa, and nNOS-β is a salt-sensitive isoform that modulates TGF. Sprague-Dawley rats received a low-, normal-, or high-salt diet for 10 days and levels of the nNOS-α, nNOS-β, and nNOS-γ were measured in the macula densa cells isolated with laser capture microdissection. Three splice variants of nNOS, α-, β-, and γ-mRNAs, were detected in the macula densa cells. After 10 days of high-salt intake, nNOS-α decreased markedly, whereas nNOS-β increased two- to threefold in the macula densa measured with real-time PCR and in the renal cortex measured with Western blot. NO production in the macula densa was measured in the perfused thick ascending limb with an intact macula densa plaque with a fluorescent dye DAF-FM. When the tubular perfusate was switched from 10 to 80 mM NaCl, a maneuver to induce TGF, NO production by the macula densa was increased by 38 ± 3% in normal-salt rats and 52 ± 6% ( P < 0.05) in the high-salt group. We found 1) macula densa cells express nNOS-α, nNOS-β, and nNOS-γ, 2) a high-salt diet enhances nNOS-β, and 3) TGF-induced NO generation from macula densa is enhanced in high-salt diet possibly from nNOS-β. In conclusion, we found that the splice variants of nNOS expressed in macula densa cells were α-, β-, and γ-isoforms and propose that enhanced level of nNOS-β during high-salt intake may contribute to macula densa NO production and help attenuate TGF.

scholarly journals Effects of NKCC2 isoform regulation on NaCl transport in thick ascending limb and macula densa: a modeling study

2014 ◽  
Vol 307 (2) ◽  
pp. F137-F146 ◽  
Author(s):  
Aurélie Edwards ◽  
Hayo Castrop ◽  
Kamel Laghmani ◽  
Volker Vallon ◽  
Anita T. Layton
Keyword(s):  
Cell Model ◽  
Basolateral Membrane ◽  
Macula Densa ◽  
Tubuloglomerular Feedback ◽  
Thick Ascending Limb ◽  
Differential Splicing ◽  
Dietary Salt ◽  
Nacl Transport ◽  
Low Salt

This study aims to understand the extent to which modulation of the Na+-K+-2Cl− cotransporter NKCC2 differential splicing affects NaCl delivery to the macula densa. NaCl absorption by the thick ascending limb and macula densa cells is mediated by apical NKCC2. A recent study has indicated that differential splicing of NKCC2 is modulated by dietary salt (Schieβl IM, Rosenauer A, Kattler V, Minuth WW, Oppermann M, Castrop H. Am J Physiol Renal Physiol 305: F1139–F1148, 2013). Given the markedly different ion affinities of its splice variants, modulation of NKCC2 differential splicing is believed to impact NaCl reabsorption. To assess the validity of that hypothesis, we have developed a mathematical model of macula densa cell transport and incorporated that cell model into a previously applied model of the thick ascending limb (Weinstein AM, Krahn TA. Am J Physiol Renal Physiol 298: F525–F542, 2010). The macula densa model predicts a 27.4- and 13.1-mV depolarization of the basolateral membrane [as a surrogate for activation of tubuloglomerular feedback (TGF)] when luminal NaCl concentration is increased from 25 to 145 mM or luminal K+ concentration is increased from 1.5 to 3.5 mM, respectively, consistent with experimental measurements. Simulations indicate that with luminal solute concentrations consistent with in vivo conditions near the macula densa, NKCC2 operates near its equilibrium state. Results also suggest that modulation of NKCC2 differential splicing by low salt, which induces a shift from NKCC2-A to NKCC2-B primarily in the cortical thick ascending limb and macula densa cells, significantly enhances salt reabsorption in the thick limb and reduces Na+ and Cl− delivery to the macula densa by 3.7 and 12.5%, respectively. Simulation results also predict that the NKCC2 isoform shift hyperpolarizes the macula densa basolateral cell membrane, which, taken in isolation, may inhibit the release of the TGF signal. However, excessive early distal salt delivery and renal salt loss during a low-salt diet may be prevented by an asymmetric TGF response, which may be more sensitive to flow increases.

scholarly journals Role of renal transporters and novel regulatory interactions in the TAL that control blood pressure

2017 ◽  
Vol 49 (5) ◽  
pp. 261-276 ◽  
Author(s):  
Lesley A. Graham ◽  
Anna F. Dominiczak ◽  
Nicholas R. Ferreri
Keyword(s):  
Blood Pressure ◽  
Salt Intake ◽  
Salt Sensitivity ◽  
Public Health Issue ◽  
Thick Ascending Limb ◽  
Dietary Salt ◽  
Therapeutic Application ◽  
Dietary Salt Intake ◽  
Renal Transporters ◽  
High Salt Intake

Hypertension (HTN), a major public health issue is currently the leading factor in the global burden of disease, where associated complications account for 9.4 million deaths worldwide every year. Excessive dietary salt intake is among the environmental factors that contribute to HTN, known as salt sensitivity. The heterogeneity of salt sensitivity and the multiple mechanisms that link high salt intake to increases in blood pressure are of upmost importance for therapeutic application. A continual increase in the kidney’s reabsorption of sodium (Na+) relies on sequential actions at various segments along the nephron. When the distal segments of the nephron fail to regulate Na+, the effects on Na+ homeostasis are unfavorable. We propose that the specific nephron region where increased active uptake occurs as a result of variations in Na+ reabsorption is at the thick ascending limb of the loop of Henle (TAL). The purpose of this review is to urge the consideration of the TAL as contributing to the pathophysiology of salt-sensitive HTN. Further research in this area will enable development of a therapeutic application for targeted treatment.

Links Between Dietary Salt Intake, Renal Salt Handling, Blood Pressure, and Cardiovascular Diseases

2005 ◽  
Vol 85 (2) ◽  
pp. 679-715 ◽  
Author(s):  
Pierre Meneton ◽  
Xavier Jeunemaitre ◽  
Hugh E. de Wardener ◽  
Graham A. Macgregor
Keyword(s):  
Blood Pressure ◽  
Cardiovascular Diseases ◽  
Salt Intake ◽  
Causal Link ◽  
Left Ventricular ◽  
High Salt ◽  
Human Populations ◽  
Dietary Salt ◽  
Dietary Salt Intake ◽  
High Salt Intake

Epidemiological, migration, intervention, and genetic studies in humans and animals provide very strong evidence of a causal link between high salt intake and high blood pressure. The mechanisms by which dietary salt increases arterial pressure are not fully understood, but they seem related to the inability of the kidneys to excrete large amounts of salt. From an evolutionary viewpoint, the human species is adapted to ingest and excrete <1 g of salt per day, at least 10 times less than the average values currently observed in industrialized and urbanized countries. Independent of the rise in blood pressure, dietary salt also increases cardiac left ventricular mass, arterial thickness and stiffness, the incidence of strokes, and the severity of cardiac failure. Thus chronic exposure to a high-salt diet appears to be a major factor involved in the frequent occurrence of hypertension and cardiovascular diseases in human populations.

Renal denervation chronically lowers arterial pressure independent of dietary sodium intake in normal rats

2003 ◽  
Vol 284 (6) ◽  
pp. H2302-H2310 ◽  
Author(s):  
Frédéric Jacob ◽  
Pilar Ariza ◽  
John W. Osborn
Keyword(s):  
Arterial Pressure ◽  
Salt Intake ◽  
Sodium Intake ◽  
Recovery Period ◽  
Control Period ◽  
Dietary Sodium ◽  
Renal Nerves ◽  
Dietary Salt ◽  
Dietary Salt Intake ◽  
High Salt Intake

The present study was designed to test the hypothesis that renal nerves chronically modulate arterial pressure (AP) under basal conditions and during changes in dietary salt intake. To test this hypothesis, continuous telemetric recording of AP in intact (sham) and renal denervated (RDNX) Sprague-Dawley rats was performed and the effect of increasing and decreasing dietary salt intake on AP was determined. In protocol 1, 24-h AP, sodium, and water balances were measured in RDNX ( n = 11) and sham ( n = 9) rats during 5 days of normal (0.4% NaCl) and 10 days of high (4.0% NaCl) salt intake, followed by a 3-day recovery period (0.4% NaCl). Protocol 2 was similar with the exception that salt intake was decreased to 0.04% NaCl for 10 days after the 5-day period of normal salt (0.04% NaCl) intake (RDNX; n = 6, sham; n = 5). In protocol 1, AP was lower in RDNX (91 ± 1 mmHg) compared with sham (101 ± 2 mmHg) rats during the 5-day 0.4% NaCl control period. During the 10 days of high salt intake, AP increased <5 mmHg in both groups so that the difference between sham and RDNX rats remained constant. In protocol 2, AP was also lower in RDNX (93 ± 2 mmHg) compared with sham (105 ± 4 mmHg) rats during the 5-day 0.4% NaCl control period, and AP did not change in response to 10 days of a low-salt diet in either group. Overall, there were no between-group differences in sodium or water balance in either protocol. We conclude that renal nerves support basal levels of AP, irrespective of dietary sodium intake in normal rats.

Effect of dietary salt on arteriolar nitric oxide in striated muscle of normotensive rats

1993 ◽  
Vol 264 (6) ◽  
pp. H1810-H1816 ◽  
Author(s):  
M. A. Boegehold
Keyword(s):  
Nitric Oxide ◽  
Vascular Tone ◽  
Striated Muscle ◽  
Salt Intake ◽  
High Salt ◽  
Dietary Salt ◽  
Dietary Salt Intake ◽  
High Salt Intake ◽  
Low Salt ◽  
Induced Hypertension

This study evaluated the influence of high dietary salt intake on nitric oxide (NO) activity in the arteriolar network of rats resistant to salt-induced hypertension. The spinotrapezius muscle microvasculature was studied in inbred Dahl salt-resistant (SR/Jr) rats fed low (0.45%)- or high (7%)-salt diets for 4–5 wk. Arterial pressures were not different between groups at any time during the study. NO synthesis inhibition with NG-nitro-L-arginine-methyl ester (L-NAME) constricted arcade arterioles in low-salt SR/Jr and dilated arcade arterioles in high-salt SR/Jr. Arcade arteriole dilation to acetylcholine (ACh), but not sodium nitroprusside (SNP), was impaired in high-salt SR/Jr. In contrast, transverse and distal arteriole responses to L-NAME, ACh, and SNP were identical in high- and low-salt SR/Jr. These findings indicate that high salt intake, in the absence of increased arterial pressure, suppresses the influence of basal and evoked NO on vascular tone in arcading arterioles, but not in smaller transverse and distal arterioles. Unaltered SNP responses in high-salt SR/Jr suggest that this effect does not involve a change in arteriolar smooth muscle responsiveness to NO.

Measured sodium excretion is associated with CKD progression: results from the KNOW-CKD study

2020 ◽  
Author(s):  
Minjung Kang ◽  
Eunjeong Kang ◽  
Hyunjin Ryu ◽  
Yeji Hong ◽  
Seung Seok Han ◽  
...  
Keyword(s):  
Salt Intake ◽  
High Salt ◽  
Uncontrolled Hypertension ◽  
Renal Outcome ◽  
Study Endpoint ◽  
Dietary Salt ◽  
Ckd Progression ◽  
Dietary Salt Intake ◽  
High Salt Intake ◽  
Increased Risk

Abstract Background Diet is a modifiable factor of chronic kidney disease (CKD) progression. However, the effect of dietary salt intake on CKD progression remains unclear. Therefore, we analyzed the effect of dietary salt intake on renal outcome in Korean patients with CKD. Methods We measured 24-h urinary sodium (Na) excretion as a marker of dietary salt intake in the prospective, multi-center, longitudinal KoreaN cohort study for Outcome in patients With CKD (KNOW-CKD). Data were analyzed from CKD patients at Stages G3a to G5 (n = 1254). We investigated the association between dietary salt intake and CKD progression. Patients were divided into four quartiles of dietary salt intake, which was assessed using measured 24-h urinary Na excretion. The study endpoint was composite renal outcome, which was defined as either halving the estimated glomerular filtration rate or developing end-stage renal disease. Results During a median (interquartile range) follow-up of 4.3 (2.8–5.8) years, 480 (38.7%) patients developed the composite renal event. Compared with the reference group (Q2, urinary Na excretion: 104.2 ≤ Na excretion &lt; 145.1 mEq/day), the highest quartile of measured 24-h urinary Na excretion was associated with risk of composite renal outcome [Q4, urinary Na excretion ≥192.9 mEq/day, hazard ratio 1.8 (95% confidence interval 1.12–2.88); P = 0.015] in a multivariable hazards model. Subgroup analyses showed that high-salt intake was particularly associated with a higher risk of composite renal outcome in women, in patients &lt;60 years of age, in those with uncontrolled hypertension and in those with obesity. Conclusions High salt intake was associated with increased risk of progression in CKD.

High dietary salt intake increases carotid blood pressure and wave reflection in normotensive healthy young men

2011 ◽  
Vol 110 (2) ◽  
pp. 468-471 ◽  
Author(s):  
Mirian J. Starmans-Kool ◽  
Alice V. Stanton ◽  
Yun Y. Xu ◽  
Simon A. McG Thom ◽  
Kim H. Parker ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Cardiovascular Disease ◽  
Body Weight ◽  
Wave Reflection ◽  
Salt Intake ◽  
High Salt ◽  
Dietary Salt ◽  
Dietary Salt Intake ◽  
High Salt Intake ◽  
Increased Risk

Dietary salt intake is associated with high brachial blood pressure (BP) and increased risk of cardiovascular disease. We investigated whether changes in dietary salt intake are associated with changes in central BP and wave reflection in healthy volunteers. Ten healthy normotensive male volunteers (22–40 yr) participated in a 6-wk double-blind randomized crossover study to compare a low-dietary salt intake (60–80 mmol sodium/day) with a high-salt intake (low salt intake supplemented with 128 mmol sodium/day) on central BP and wave reflection. Brachial and carotid BP, carotid blood flow velocity, forward (Pf) and backward (Pb) pressure, wave intensity, body weight, and urinary electrolyte excretion were measured at the end of each crossover period. High salt intake significantly increased carotid systolic BP [98 (SD 11) vs. 91 mmHg (SD 13), P < 0.01] and increased wave reflection [ratio of backward to forward pressure (Pb/Pf) 0.13 (SD 0.02) vs. 0.11 (SD 0.03), P = 0.04] despite only small effects on brachial BP [114 (SD 9) vs. 112 mmHg (SD 6), P = 0.1]. Urinary sodium excretion and body weight were also increased following high salt intake. High salt intake disproportionately increases central BP compared with brachial BP as a result of enhanced wave reflection. These effects may contribute to the adverse effect of high dietary salt intake on the risk of cardiovascular disease.

Dietary salt intake modulates differential splicing of the Na-K-2Cl cotransporter NKCC2

2013 ◽  
Vol 305 (8) ◽  
pp. F1139-F1148 ◽  
Author(s):  
Ina Maria Schieβl ◽  
Agnes Rosenauer ◽  
Veronika Kattler ◽  
Will W. Minuth ◽  
Mona Oppermann ◽  
...  
Keyword(s):  
Angiotensin Ii ◽  
Salt Intake ◽  
Sucrose Solution ◽  
Salt Content ◽  
Sodium Reabsorption ◽  
Thick Ascending Limb ◽  
Differential Splicing ◽  
Dietary Salt ◽  
Dietary Salt Intake ◽  
Low Salt

Both sodium reabsorption in the thick ascending limb of the loop of Henle (TAL) and macula densa salt sensing crucially depend on the function of the Na/K/2Cl cotransporter NKCC2. The NKCC2 gene gives rise to at least three different full-length NKCC2 isoforms derived from differential splicing. In the present study, we addressed the influence of dietary salt intake on the differential splicing of NKCC2. Mice were subjected to diets with low-salt, standard salt, and high-salt content for 7 days, and NKCC2 isoform mRNA abundance was determined. With decreasing salt intake, we found a reduced abundance of the low-affinity isoform NKCC2A and an increase in the high-affinity isoform NKCC2B in the renal cortex and the outer stripe of the outer medulla. This shift from NKCC2A to NKCC2B during a low-salt diet could be mimicked by furosemide in vivo and in cultured kidney slices. Furthermore, the changes in NKCC2 isoform abundance during a salt-restricted diet were partly mediated by the actions of angiotensin II on AT1 receptors, as determined using chronic angiotensin II infusion. In contrast to changes in oral salt intake, water restriction (48 h) and water loading (8% sucrose solution) increased and suppressed the expression of all NKCC2 isoforms, without changing the distribution pattern of the single isoforms. In summary, the differential splicing of NKCC2 pre-mRNA is modulated by dietary salt intake, which may be mediated by changes in intracellular ion composition. Differential splicing of NKCC2 appears to contribute to the adaptive capacity of the kidney to cope with changes in reabsorptive needs.

Salt-resistant blood pressure and salt-sensitive renal autoregulation in chronic streptozotocin diabetes

2009 ◽  
Vol 296 (6) ◽  
pp. R1761-R1770 ◽  
Author(s):  
Catherine Lau ◽  
Ian Sudbury ◽  
Michael Thomson ◽  
Perry L. Howard ◽  
Alex B. Magil ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Salt Intake ◽  
Collecting Duct ◽  
Periodic Acid ◽  
Systolic Pressure ◽  
Diabetic Rats ◽  
Tubuloglomerular Feedback ◽  
Dietary Salt ◽  
Periodic Acid Schiff ◽  
High Salt Intake

Hyperfiltration occurs in early type 1 diabetes mellitus in both rats and humans. It results from afferent vasodilation and thus may impair stabilization of glomerular capillary pressure by autoregulation. It is inversely related to dietary salt intake, the “salt paradox.” Restoration of normal glomerular filtration rate (GFR) involves increased preglomerular resistance, probably mediated by tubuloglomerular feedback (TGF). To begin to test whether the salt paradox has pathogenic significance, we compared intact vs. diabetic (streptozotocin) Long-Evans rats with normal and increased salt intake, 1 and ∼3% by weight of food eaten, respectively. Weekly 24-h blood pressure records were acquired by telemetry before and during diabetes. Blood glucose was maintained at ∼20 mmol/l by insulin implants. GFR was significantly elevated only in diabetic rats on normal salt intake, confirming diabetic hyperfiltration and the salt paradox. Renal blood flow dynamics show strong contributions to autoregulation by both TGF and the myogenic mechanism and were not impaired by diabetes or by increased salt intake. Separately, systolic pressure was not elevated in diabetic rats at any time during 12 wk with normal or high salt intake. Autoregulation was effective in all groups, and the diabetic-normal salt group showed significantly improved autoregulation at low perfusion pressures. Histological examination revealed very minor glomerulosclerosis and modest mesangial expansion, although neither was diagnostic of diabetes. Periodic acid-Schiff-positive droplets found in distal tubules and collecting duct segments were diagnostic of diabetic kidneys. Biologically significant effects attributable to increased salt intake were abrogation of hyperfiltration and of the left shift in autoregulation in diabetic rats.

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