Na In Urine Research Articles

PF-06869206 is a selective inhibitor of renal Pi transport: evidence from in vitro and in vivo studies.

Plasma phosphate (Pi) levels are tightly controlled, and elevated plasma Pi levels are associated with an increased risk of cardiovascular complications and death. Two renal transport proteins mediate the majority of Pi reabsorption: Na+-phosphate cotransporters Npt2a and Npt2c, with Npt2a accounting for 70-80% of Pi reabsorption. The aim of the present study was to determine the in vitro effects of a novel Npt2a inhibitor (PF-06869206) in opossum kidney (OK) cells as well as determine its selectivity in vivo in Npt2a knockout (Npt2a-/-) mice. In OK cells, Npt2a inhibitor caused dose-dependent reductions of Na+-dependent Pi uptake (IC50: ~1.4 μmol/L), whereas the unselective Npt2 inhibitor phosphonoformic acid (PFA) resulted in an ~20% stronger inhibition of Pi uptake. The dose-dependent inhibitory effects were present after 24 h of incubation with both low- and high-Pi media. Michaelis-Menten kinetics in OK cells identified an ~2.4-fold higher Km for Pi in response to Npt2a inhibition with no significant change in apparent Vmax. Higher parathyroid hormone concentrations decreased Pi uptake equivalent to the maximal inhibitory effect of Npt2a inhibitor. In vivo, the Npt2a inhibitor induced a dose-dependent increase in urinary Pi excretion in wild-type mice (ED50: ~23 mg/kg), which was completely absent in Npt2a-/- mice, alongside a lack of decrease in plasma Pi. Of note, the Npt2a inhibitor-induced dose-dependent increase in urinary Na+ excretion was still present in Npt2a-/- mice, a response possibly mediated by an off-target acute inhibitory effect of the Npt2a inhibitor on open probability of the epithelial Na+ channel in the cortical collecting duct.

Validation of diagnostic usefulness of the spot urine Na/K ratio for replacement of 24-hour urine NA excretion in cirrhotic patients with ascites

Validation of diagnostic usefulness of the spot urine Na/K ratio for replacement of 24-hour urine NA excretion in cirrhotic patients with ascites

Association of urinary sodium and potassium excretion with systolic blood pressure in the Dietary Approaches to Stop Hypertension Sodium Trial

The 2019 National Academy of Science, Engineering and Medicine Dietary Reference Intakes (DRI) for Sodium (Na+) and Potassium (K+) Report concluded there remains insufficient evidence to establish a K+ DRI. This study tested the hypothesis that reduced Na+ and increased K+ excretion will positively associate with lower blood pressure in salt sensitive (SS) and salt resistant (SR) participants in the Dietary Approaches to Stop Hypertension Sodium Trial (DASH–Sodium). Via the NHLBI BioLINCC we accessed the DASH-Sodium dataset for data on systolic blood pressure (SBP), 24-h urinary Na+ and K+ excretion at screening (regular patient diet; N = 186, SS N = 222 SR) and post DASH diet (N = 71 SS, N = 119 SR). The relationships between SBP, urinary Na+ and K+ excretion, and Na+/K+ ratio were assessed via linear regression. At screening elevated urinary Na+ excretion positively associated with SBP in SS (1 g increase in urinary Na+ excretion = +1 0 ± 0.4 mmHg) but not SR participants, and urinary K+ excretion of <1 g K+/day was associated with higher SBP in SS and SR participants. Urinary K+ excretion ≥1 g/day, or a decreases in urinary Na+/K+ ratio, was not associated with lower SBP. Post the DASH–sodium diet intervention, SBP was reduced in SS and SR participants. However, no correlation was observed between reduced SBP and urinary K+ excretion or the urinary Na+/K+ ratio irrespective of the salt sensitivity of blood pressure. Our data support the DRI recommendation not to establish a K+ DRI and suggest further evidence is required to support a reduced Na+/K+ ratio to lower SBP.

Correlation of excess salt intake identified by the survey with urine sodium level and blood pressure: data of ESSE-RF study

Aim. To study the association of blood pressure (BP) and hypertension (HTN) with salt intake estimated by the survey and the urinary Na+ concentration among men and women 25-64 years old, examined within the ESSE-RF and ESSE-RF-2 studies.Material and methods. Representative samples of the Russian population aged 25-64 years were examined. At the first phase in 2012-2014, 21,888 people (men — 38,2%) were included, and at the second phase in 2017 — 6,714 people (men — 44,7%). The response rate was 80%. We used standard questionnaire. Adding more salt and the consumption of salted foods (sausages, deli meats, and pickled foods) in the criteria “daily or almost daily” was considered excess salt intake (ESI). BP measurement was carried out in a sitting position on the right hand. BP was measured twice with an interval of about 2-3 minutes. HTN was diagnosed at a systolic BP (SBP) ≥140 mm Hg and/or diastolic BP ≥90 mm Hg, or in case of antihypertensive therapy. In ESSE-RF-2, an analysis of the morning urine was additionally performed. Na+ was determined using the EX-Ds ion-selective electrolyte analyzer. All participants were stratified by the quintiles of urine sodium level. Data analysis was performed using the software package R 3.6.1. The models of linear and logistic regression were used. The differences were considered at p&lt;0,05.Results. The average level of SBP significantly increases with an increase in Na+ in urine: 1,04 (0,60-1,48) mm Hg for the quintile of sodium distribution (p&lt;0,001), the odds of HTN increases by 1,11 (1,05-1,17) times for the quintile (p&lt;0,001). Questionnaire components of ESI are also significantly related to urinary Na+ levels. The consumption of sausages and deli meats has the greatest effect, causing an increase in the average Na+ level by 11,59 (7,06-16,12) mmol/l (p&lt;0,001). The applied point scale is significantly related to urine sodium level and predicts HTN no worse than Na+ in the urine (p=0,15 for the difference hypothesis). One point on the scale increases the Na+ level by an average of 7,51 (5,01-10,02) mmol/l, SBP by an average of 0,74 (0,41-1,07) mm Hg and the odds of HTN by 1,1 (1,06-1,15) times (p&lt;0,001 for all).Conclusion. In the pattern of ESI components, processed meat and sausage products take first place in terms of association strength with urine sodium. The questionnaire used to assess the proportion of people with ESI can be recommended for assessing this risk factor during screening. ESI detected by the questionnaire is associated with elevated BP and urinary Na+ values.

Effects of prostaglandin E combined with continuous renal replacement therapy on septic acute kidney injury.

The effects of prostaglandin E (PGE) combined with continuous renal replacement therapy (CRRT) on renal function and inflammatory responses in patients with septic acute kidney injury (SAKI) remain unclear. To investigate the effects of PGE combined with CRRT on urinary augmenter of liver regeneration (ALR), urinary Na+/H+ exchanger 3 (NHE3), and serum inflammatory cytokines in patients with SAKI. The clinical data of 114 patients with SAKI admitted to Yichang Second People's Hospital from May 2017 to January 2019 were collected. Fifty-three cases treated by CRRT alone were included in a control group, while the other 61 cases treated with PGE combined with CRRT were included in an experimental group. Their urinary ALR, urinary NHE3, serum inflammatory cytokines, renal function indices, and immune function indices were detected. Changes in disease recovery and the incidence of adverse reactions were observed. The 28-d survival curve was plotted. Before treatment, urinary ALR, urinary NHE3, blood urea nitrogen (BUN), serum creatinine (SCr), CD3+ T lymphocytes, CD4+ T lymphocytes, and CD4+/CD8+ T lymphocyte ratio in the control and experimental groups were approximately the same. After treatment, urinary ALR and NHE3 decreased, while BUN, SCr, CD3+ T lymphocytes, CD4+ T lymphocytes, and CD4+/CD8+ T lymphocyte ratio increased in all subjects. Urinary ALR, urinary NHE3, BUN, and SCr in the experimental group were significantly lower than those in the control group, while CD3+ T lymphocytes, CD4+ T lymphocytes, and CD4+/CD8+ T lymphocyte ratio were significantly higher than those in the control group (P < 0.05). After treatment, the levels of tumor necrosis factor-α, interleukin-18, and high sensitivity C-reactive protein in the experimental group were significantly lower than those in the control group (P < 0.05). The time for urine volume recovery and intensive care unit treatment in the experimental group was significantly shorter than that in the control group (P < 0.05), although there was no statistically significant difference in hospital stays between the two groups. The total incidence of adverse reactions did not differ statistically between the two groups. The 28-d survival rate in the experimental group (80.33%) was significantly higher than that in the control group (66.04%). PGE combined with CRRT is clinically effective for treating SAKI, and the combination therapy can significantly improve renal function and reduce inflammatory responses.

Correlation Between Spot Urine Sodium, 24 Hour Urinary Sodium and Food Frequency Questionnairein Estimation of Salt Intake in Healthy Individuals

Background:Salt intake is a known contributor to increased blood pressure. However, it is rarely monitored in clinical practice. 24-hr urinary sodium (24-HrNa) is the gold standard method to estimate salt intake but this method is rather burdensome.Objective: The objective of this study is to correlate between spot urine sodium (SUNa), 24-HrNa and Na intake estimation by food frequency questionnaire (FFQ) (FFQNa).Methods : 430 healthy participants aged between 20-40 years old were recruited. Second morning voided urine samples were obtained from all participants to estimate SUNa. 24-HrNa samples were obtained from 77 out of 430 participants. All participants were required to answer a validated FFQ. Urine samples were analysed for Na using indirect ion-selective electrode (ISE) method. Daily sodium intake was calculated from the FFQ.Results:The mean daily sodium intake from 24-hrNa (n=77) was 155 mmol/day, SUNa (n=430) was 158 mmol/L and FFQNa (n=430) was 271 mmol/day. There was a moderate correlation between SUNa and 24-hrNa (ρ = 0.62, P &lt; 0.000). No correlation was seen between both 24-hrNa and SUNa with FFQNa (ρ = 0.035, P = 0.768 and ρ = 0.026, P = 0.597 respectively).Conclusion: Spot urine Na is a simple cost-effective method to estimate daily Na intake and has the potential to replace 24-hour urinary Na.International Journal of Human and Health Sciences Vol. 05 No. 01 January’21 Page: 74-80

Re: Comment on "The Clinical Importance of the Plasma Atherogenic Index, Other Lipid Indexes, and Urinary Sodium and Potassium Excretion in Patients with Stroke".

Objective Cardiovascular complications are still the primary reason for high mortality rates worldwide. The determination of risk factors is important to prevent stroke. The aim of the present study was to analyze the importance of serum lipid indexes and urinary sodium (Na)/potassium (K) excretion in patients with stroke together with sex differences. Materials and methods A total of 50 (28 male and 22 female, mean age 65.9±14.6 years) patients with acute stroke were included in the study group, and 32 body mass index-matched healthy subjects were included in the control group. Lipid profiles [(cholesterol, triglyceride, very low-density lipoprotein, low-density lipoprotein, and high-density lipoprotein (HDL)], serum creatinine (Cre), erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), and Na, K, and Cre excretion in spot urine samples of the patients were recorded. Results Systolic blood pressure (p=0.021), ESR (p=0.044), and CRP (p=0.042) were significantly higher in all patients in the stroke group; urinary Tanaka (K) (p=0.033), Kawazaki (K) (p=0.028), urinary spot Cre (p=0.012), and Na excretion (p=0.036) levels were found to be significantly lower in only male patients with stroke. The mean plasma atherogenic indexes were 0.57±0.24 in the study (stroke) group and 0.54±0.22 in the control group (p=0.61). Other lipid indexes, such as Castelli's risk index (CRI)-I (p=0.29), CRI-II (p=0.24), atherogenic coefficient (p=0.29), and non-HDL cholesterol (p=0.69), were not statistically different from the controls. Conclusion Urinary Na, K, and Cre excretion was significantly lower in male patients with stroke, and acute phase reactants were significantly higher in the entire stroke group than in controls. These parameters can be used as auxiliary biomarkers in the risk assessment of stroke.

4438 Twenty-four-hour Urinary Sodium Excretion Estimated from a Spot Urine Sample May Be Used as an Indicator of Intake in CKD Patients

OBJECTIVES/GOALS: Sodium (Na) intake can elevate blood pressure and is a factor in developing chronic kidney disease (CKD). Twenty-four-hour urinary Na (24hUNa) is the gold standard for assessing Na intake but is burdensome. Validated equations estimate 24hUNa (e24hUNa) from a spot urine sample, but these estimations are not validated against a known Na intake in CKD. METHODS/STUDY POPULATION: The current study is a secondary analysis of a 9-day controlled feeding study in moderate CKD patients matched to healthy adults. Only CKD patients were used for the current analyses (n = 8). Participants consumed a controlled diet for 9 days, providing ~2400 mg Na/d as determined by inductively coupled plasma optical emission spectroscopy (ICP). On days 7 and 8, participants collected all urine in an inpatient setting, beginning with a fasting sample on day 7. Urine sample mineral analyses were performed by ICP and urinary creatinine by the Jaffe reaction. The day 7 fasting urine sample was used to calculate e24hUNa using 6 published equations. Log-transformed Na intake, measured 24hUNa, and e24hUNa were compared by repeated-measures ANOVA with planned contrasts using SAS. RESULTS/ANTICIPATED RESULTS: Fifty percent of the CKD patients (n = 4) were female; 63% (n = 5) were white, and 37% (n = 3) were black. On average, participants were aged 56.6 ± 13.8 y with a BMI of 31.7 ± 9.4 kg/m2 and eGFR of 40.7 ± 7.9 mL/min. Based on actual food intake, average Na intake on day 7 was 2024 ± 388 mg. Average measured 24hUNa was 2529 ± 1334 mg. The main ANOVA was significant (p = 0.02). Results from the planned contrasts found that e24hUNa from the SALTED cohort, an equation developed specifically for CKD patients, was significantly higher than both Na intake (p&lt;0.001) and measured 24hUNa (p = 0.007). For the remaining 5 equations, e24hUNa was not significantly different from measured 24hUNa nor dietary Na intake. DISCUSSION/SIGNIFICANCE OF IMPACT : Our results suggest that e24hUNa calculated using most published equations may provide a reliable and low-burden method of assessing dietary Na intake in moderate CKD patients. These findings should be confirmed in larger samples. Additional studies are needed to validate or dispute the use of the SALTED equation for estimating Na intake.

Using Spot Urine Samples to Estimate Sodium and Potassium intake in Healthy vs CKD Patients: Results from a Controlled Feeding Study

Abstract Objectives Evaluating sodium (Na) and potassium (K) intake is important as both have implications for blood pressure and cardiovascular health, especially in individuals with chronic kidney disease (CKD). Spot urine samples may be used to estimate Na and K intake with several published equations, but the accuracy has not been thoroughly explored. Our objective was to compare estimated 24-hour urinary Na and K excretion (e24hUNa and e24hUK), calculated from a spot urine sample using published equations, to measured 24hUNa and 24hUK and Na and K intake, and to determine if there are differences between healthy and CKD participants. Methods This is a secondary analysis of a controlled feeding study in participants with moderate CKD matched to healthy adults (n = 16). Participants consumed a controlled diet for 9 days, providing ∼2400 mg Na/d and ∼3000 mg K/d. On days 7 and 8, participants collected all urine in an inpatient setting. Urine Na and K were analyzed by ICP and urine creatinine by the Jaffe reaction. The day 7 fasting urine sample was used to calculate e24hUNa using 2 equations and e24huK using 1 equation. Log-transformed Na intake, measured 24hUNa, and e24hUNa were compared using a general linear mixed model and partial correlations, and agreement between Na intake and e24hUNa was assessed using Bland-Altman plots. Similar analyses were run for K. Results Participants were aged 54.6 ± 13.0 y, n = 8 were female, n = 6 were black, and n = 10 were white. In CKD participants, eGFR was 40.7 ± 7.9 mL/min. Average Na intake on day 7 was 2138 ± 302 mg and K intake was 2528 ± 254 mg. Na intake, measured 24hUNa, and e24hUNa were not significantly different (P = 0.17) or correlated with each other (all P &amp;gt; 0.20) and there was no significant interaction with CKD status (P = 0.51). However, both e24hUNa were ∼500 mg higher than Na intake. For K, e24hUK was significantly different from K intake (P &amp;lt; 0.001) and measured 24hUK (P = 0.02), with no interaction with CKD (P = 0.53). K intake, measured 24hUK, and e24hUK were not correlated (all P &amp;gt; 0.05). Bland-Altman plots show poor agreement between both e24hUNa and Na intake and e24hUK and K intake. Conclusions Estimated 24hUNa and estimated 24hUK are poor predictors of Na and K intake, respectively, in both healthy and CKD participants. Results should be confirmed in a larger sample. Funding Sources Indiana CTSI (funded by NCATS CTSA program), NIDDK.

Normal-range urinary albumin excretion associates with blood pressure and renal electrolyte handling in pregnancy.

Albuminuria in the pathological range is a significant predictor of preeclampsia. In healthy persons, high normal urinary albumin predicts a later incidence of hypertension and is associated with salt sensitivity of blood pressure. We hypothesized that in pregnancy urinary albumin in the normal range associates with blood pressure through activation of distal Na+ reabsorption and renal salt retention by plasma factors cofiltered with albumin. We analyzed 24-h urine collections and plasma samples from gestational week 29 of 560 pregnant women from the Odense Child Cohort, a Danish population-based cohort. Plasma and urinary aldosterone were measured by ELISA. Plasma and urinary Na+, K+, Cl-, and creatinine were also determined. Predictive values of urinary albumin were assessed by linear mixed, multiple, and Cox regression analyses. Primary outcomes were blood pressure and renal electrolyte handling. Twenty-four-hour urinary albumin excretion at gestational week 29 associated with gestational blood pressure trajectory, with adjusted β coefficients (95% confidence intervals) for each 10-fold increase in urinary albumin as follows: 5.71 (1.60 to 9.81) mmHg for systolic blood pressure and 4.39 (1.41 to 7.38) mmHg for diastolic blood pressure. Urinary albumin was inversely associated with fractional excretion rates of Na+, K+, and Cl-, with adjusted β coefficients (95% confidence intervals) for each 10-fold increase in urine albumin as follows: -0.25 (-0.35 to -0.14), -5.06 (-6.81 to -3.30), and -0.28 (-0.41 to -0.15), respectively. In conclusion, at gestational week 29, urinary albumin excretion in the normal range associated with blood pressure and renal electrolyte handling independent of potential confounders.

SUN-284 Rare Case of Adipsic Diabetes Insipidus Post Astrocytoma Resection: Case Report

Background:Adipsic diabetes insipidus (ADI) is a rare disorder triggered by injury to the hypothalamus impairing thirst osmoreceptors and the antidiuretic hormone syntheses leading to absence of thirst.We are reporting a rare case of ADI Post astrocytoma resection who presented with a severe hypernatremia postoperatively.Clinical Case:A 16-year-old female known to have hypothalamic pilocystic astrocytoma post incomplete resection in 2014.She presented in 2018 with one week history of sudden onset heachache, progressively worsen overtime, worst in the morning, there were no relieving factors. On examination she was conscious alert oriented GCS 15/15, Vital signs were normal, fundus exam within normal, pupil equal bilateral reactive to light, there was no focal neurological deficit. Systemic examination was unremarkable. Radiological imaging revealed interval size progression of previously seen suprasella region with extension into the floor of the third ventricle. Investigations: Renal profile & pituitary hormonal profile were normal. She underwent second stage resection.Postoperatively, she developed asymptomatic hypernatremia with inability to sense thirst. On examination: Conscious, alert, BP:100/65, no postural drop, Pulse:95, Fluid balance negative 1L. Systemic examination was unremarkable. Laboratory investigations: Creat 0.77mg/dl (0.6–1), Na 173mEq/dl(136–145), K 3.3mEq/dl(3.5–5.1), Cl 134mEq/dl(98–107), Serum osmolality 363mOs/kg(285 -295), Urine osmolality 468mOs/kg(300 -1600), Urine Na 29mEq/L(20- 110) & Urine volume 1900. Diagnosis of ADI was made where she was treated with desmopressin. Her response was good with reduction in Na level of around 7- 9 mEq/L/Day. She was maintained on twice daily vasopressin, instructed to maintain her fluid intake 1–1.5 L/day and good urine output.Conclusions:Astrocytoma rarely linked with development of central diabetes insipidus and even fewer with adipsia. The absence of polydipsia and polyuria can be misleading. Long-term therapy should consider the benefits of vasopressin and fluid therapy against the risk of brain edema/herniation. Body weight and electrolytes monitoring essential & should be maintained a long with strict fluid intake.

Impaired Renal Endothelin‐1 Excretion in Diet‐induced Obesity Contributes to Salt Sensitivity in Male Sprague‐Dawley Rats

The renal endothelin system is an important regulator of sodium excretion in response to high salt intake. Urinary Na+ excretion (UNaV) as well as endothelin‐1 (ET‐1) excretion follow a diurnal rhythm, which is controlled by central and peripheral clock genes. Decreased renal medullary ET‐1 secretion has been attributed to salt sensitive (SS) hypertension. Diet‐induced obesity leads to clock gene dysfunction and Na+ imbalance. However, it is not clear how a high fat (HF) diet could influence the diurnal regulation of these systems. Our overarching hypothesis is that HF diet contributes to the development of salt‐sensitive hypertension through renal ET‐1 dysfunction. Male Sprague‐Dawley rats were put on either high fat (45 Kcal% fat, HF) or normal fat (10 Kcal% fat, NF) diet for 8 weeks duration starting at 6 weeks of age. Half‐way through the feeding protocol, rats were implanted with telemetry transmitters for continuous blood pressure measurement. For the last 2 weeks of feeding, HF and NF groups were divided into 2 subgroups to receive an additional high salt (4% NaCl, HS) diet or continue on the normal salt (0.3% NaCl, NS) diet with continuous blood pressure monitoring. For the last 4 days of the feeding protocol, rats were put in metabolic cages for 2 days of acclimation, and then urine was collected and food and water intakes were monitored in 12‐hr increments (inactive‐lights on/active‐lights off) for the subsequent 2 days. Systolic blood pressure (BP) was significantly increased in HF compared to NF rats after 6 weeks of feeding (145 ± 1 vs 138 ± 2 mmHg, n =14 and 11 respectively) during their active period. Chronic HS diet led to a further increase in active‐time systolic BP in HF rats compared to their NS control (153 ± 2 vs 146 ± 2 mmHg, n =6/group), while addition of HS to the NF group showed no significant increase in systolic BP (145 ± 2 vs 140 ± 3 mmHg, n =6/group) during the active period. The NF group on HS diet had a significant increase in active period ET‐1 excretion compared to NF/NS (4.34 ± 0.35 vs 1.65 ± 0.38 pg/12hrs, n= 6/group). However, HS diet failed to increase active period ET‐1 excretion in the HF (2.56 ±0.29 vs 1.32 ± 0.12 pg/12 hrs, n=6/group) compared to their NS controls. Rats on HF/NS and NF/NS diets were given an acute salt load of 900 μEq NaCl in 1 ml water, i.p. to assess their acute natriuretic response. The natriuretic response to an acute salt load given at the beginning of the active period was significantly reduced in rats on HF vs. NF with ⊗UNaV of 629 ± 91 vs 985 ± 75 μEq/12 hrs in the first 12 hours post‐load, respectively, n= 6/group. This was associated with attenuated ET‐1 excretion in HF versus NF diet (0.93 ± 0.15 vs 1.69 ± 0.16 pg/12hrs, respectively, n=11/group). There were no significant differences in the natriuretic response when the salt load was given at the beginning of the inactive period. These data show that HF diet reduces renal ET‐1 and salt handling in a time of day dependent manner. These findings are also consistent with our hypothesis that timing of Na+ handling may contribute to salt‐sensitive hypertension in diet‐induced obesity.Support or Funding InformationFunded by P01 HL136267 to DMP

Endothelin Receptor A and B Co‐operate to Mediate GPER‐induced Natriuresis

G protein‐coupled estrogen receptors (GPER) are membrane‐associated receptors that mediate rapid estrogenic signaling. We recently found that activation of GPER in the renal medulla of female rats, but not males, evokes endothelin‐dependent natriuresis. Endothelin‐1 (ET‐1) inhibits tubular reabsorption of Na+ via stimulating ET receptor B (ETB). Evidence points that ET receptor A (ETA) may contribute to natriuresis in female rats only. The current study was designed to identify whether GPER‐induced natriuresis is mediated via activation of renal medullary ETA and/or ETBreceptors in female rats. We determined the effect of stimulating GPER in the renal medulla on urine flow and urinary Na+ excretion in anesthetized female ETB deficient rats (ETB def) and transgenic (TG) controls. We infused saline to the renal medullary interstitium during an equilibration period of 60–80 min at a flow rate of 500 μl/h, followed by vehicle, then the GPER selective agonist, G1 (5 pmol/kg/min). Infusion of G1 to the renal medulla increased urine flow and Na+excretion in TG control animals (from 4.77 ± 1.19 to 7.36 ± 2.41 μl/min and from 0.47 ± 0.09 to 0.91 ± 0.27 μmol/min, respectively, n=7, p&lt;0.05). Similarly, medullary GPER activation evoked a diuretic and natriuretic response in ETB def rats (urine flow: from 4.07 ± 0.47 to 6.52 ± 1.01 μl/min and Na+ excretion: from 0.29 ± 0.06 to 0.64 ± 0.16 μmol/min, respectively, n=8, p&lt;0.05). G1 infusion did not change blood pressure or urinary K+ excretion in ETB def or TG control animals. Mean arterial blood pressure was higher in ETB def rats, compared to TG controls (117 ± 6 vs. 99 ± 3 mmHg, n=7–8, p&lt;0.05). We also determined the physiological response to medullary GPER activation in anesthetized female Sprague Dawley rats after individual blockade of ETA or ETB receptors, achieved by an intravenous bolus injection of ABT‐627 (5mg/kg) or A‐192621 (10 mg/kg), respectively, or vehicle. Neither selective antagonism of ETA nor ETB antagonism impacted the diuretic or natriuretic actions of G1. However, simultaneous blockade of ETA and ETB receptors abolished G1‐evoked diuresis and natriuresis. Blood pressure and urinary K+ excretion remained unchanged during G1 infusion in the presence or absence of ET receptor antagonists. Thus, using pharmacological and genetic approaches, our study reveals that ETA and ETB receptors in the renal medulla work co‐operatively to mediate the diuretic and natriuretic response to GPER activation.Support or Funding InformationFunded by AHA 18CDA34110010 and K99DK119413 to EYG and P01 HL136267 to DMP.

The Deletion of AT1a Receptors Selectively in The Proximal Tubules of The Kidney Lowers Blood Pressure by Inducing Glomerular Hyperfiltration and Pressure‐Natriuresis Responses in PT‐Agtr1a−/− Mice

The renin‐angiotensin system (RAS) in the proximal tubules of the kidney plays a key role in the physiological regulation of proximal tubular Na+ reabsorption and normal blood pressure homeostasis. Inappropriate activation of intratubular RAS in the proximal tubules may contribute to angiotensin II (Ang II)‐induced hypertension. In the present study, we used proximal tubule‐specific knockout of AT1a receptors (PT‐Agtr1a−/−) in the kidney to test the hypothesis that Ang II and AT1a receptors in the proximal tubules are required for normal blood pressure homeostasis and full development of Ang II‐induced hypertension by altering glomerular filtration and the pressure‐natriuresis responses. To test the hypothesis, six groups (n=7–12 per group) of adult male wild‐type (WT) and PT‐Agtr1a−/− mice were infused with or without Ang II via osmotic minipump for 2 weeks (1.5 mg/kg, i.p.). Glomerular filtration rate (GFR) was monitored by an intradermal device using fluorescein‐labeled sinistrin, and natriuretic responses were determined under basal conditions and after Ang II infusion for 2 weeks. Basal systolic blood pressure were ~13 ± 3 mmHg lower in PT‐Agtr1a−/− than WT mice (P&lt;0.01). However, basal GFR was significantly higher in PT‐Agtr1a−/− mice (WT: 160.4 ± 7.0 μl/min vs. PT‐Agtr1a−/−: 186.0 ± 10 μl/min, P&lt;0.01). Basal 24 h urinary Na+ excretion (UNaV) was significantly higher in PT‐Agtr1a−/− than WT mice (P&lt;0.01). In response to Ang II infusion, both WT and PT‐Agtr1a−/− mice developed hypertension, and the magnitude of the pressor response to Ang II was similar in WT (Δ43 ± 3 mmHg, P&lt;0.01) and PT‐Agtr1a−/− mice (Δ39 ± 5 mmHg, P&lt;0.01). However, the absolute systolic blood pressure level was still 16 ± 3 mmHg lower in PT‐Agtr1a−/− mice (P&lt;0.01). Ang II significantly decreased GFR to 132.2 ± 7.0 μl/min in WT mice (P&lt;0.01), and to 129.4 ± 18.6 μl/min in PT‐Agtr1a−/− mice (P&lt;0.01), respectively. In WT mice, UNaV increased from 139.3 ± 22.3 μmol/24 h in the control group to 196.4 ± 29.6 μmol/24 h in the Ang II‐infused group (P&lt;0.01). In PT‐Agtr1a−/− mice, UNaV increased from 172.0 ± 10.2 μmol/24 h in the control group to 264.7 ± 35.4 μmol/24 h in the Ang II‐infused group (P&lt;0.01). The pressor response to Ang II was attenuated, while the natriuretic response was augmented by losartan in WT and PT‐Agtr1a−/− mice (P&lt;0.01). Finally, proximal tubule‐specific deletion of AT1a receptors significantly augmented the pressure‐natriuresis response and natriuretic responses to acute saline infusion (P&lt;0.01) or a 2% high salt diet for 2 weeks (P&lt;0.01). In conclusion, the present study supports the hypothesis that Ang II and AT1a receptors in the proximal tubules are required for normal blood pressure homeostasis and the full development of Ang II‐induced hypertension, and suggest that deletion of AT1a receptors selectively in the proximal tubules lowers basal blood pressure by inducing glomerular hyperfiltration and promoting the natriuretic response in PT‐Agtr1a−/− mice.Support or Funding InformationThis work was supported in part by NIDDK grants, 2R01DK067299‐06A2, 2R01DK067299‐10A1, 5R01DK102429‐01, and 2R01DK102429‐03A1 to Dr. Zhuo.

Generation and Characterization of Thick Ascending Limb‐Specific NHE3 Knockout Mice

The Na+/H+ exchanger 3 (NHE3) mediates Na+ absorption in the intestine and reabsorption in the kidney, thereby playing a key role in fluid homeostasis and blood pressure regulation. NHE3 is expressed in the luminal membrane of the renal proximal tubule (PT), where the majority of renal Na+ reabsorption (~67%) occurs. In addition, NHE3 is expressed substantially in the thick ascending limb (TAL). Whole body NHE3 knockout mice exhibit hypovolemia, hypotension, diarrhea, metabolic acidosis and renal Na+ wasting. Studies in kidney‐specific (PT and TAL) NHE3 knockout mice showed a rather mild phenotype in terms of Na+ homeostasis and no acid‐base phenotype (Kidney International; 2017,92:397–414). To determine the physiological role of NHE3 in the TAL we generated a novel tamoxifen (Tam)‐inducible TAL‐specific NHE3 knockout (NHE3TAL‐KO) mouse model by crossing NHE3loxlox (Control, Con) with uromodulin Cre (UmodCreERT2) mice. After Tam administration (3 days, 67 mg/kg via oral gavage), TAL‐specific NHE3 knockout was confirmed by quantitative RT‐qPCR for NHE3 in microdissected inner medulla/inner stripe outer medulla (ISOM) and renal cortex and by immunofluorescent labeling with NHE3 (PT and TAL), NKCC2 (TAL marker) and lotus tetragonolobus lectin (LTL, PT marker). NHE3 mRNA levels in NHE3TAL‐KO mice (n=8) were reduced by 30% in the renal cortex and by 94% in the ISOM. Control mice showed colocalization of NHE3 with LTL and NKCC2; in contrast, no immunofluorescence was observed for NHE3 in the TAL of NHE3TAL‐KO mice. NHE3TAL‐KO mice were born at predicted Mendelian frequencies, appeared grossly indistinguishable from Con mice, and developed normally. Two weeks after Tam administration, NHE3TAL‐KO mice (n=11) showed a ~25% lower urine osmolality compared to Con mice (n=10) (2224±90 versus 1826±93 mOsm/kg, P&lt;0.05) associated with ~20% higher water intake (5.3±0.2 versus 6.3±0.3 mL/day, P&lt;0.05). Blood pH was slightly but significantly increased in NHE3TAL‐KO mice (n=20) versus Con mice (n=19) (7.39±0.01 versus 7.37±0.01, P&lt;0.05), which was associated with a tendency of higher blood HCO3− in NHE3TAL‐KO mice (26.1±0.4 versus 25.5±0.3 mmol, P=0.07). However, no differences were observed for urinary pH (6.1±0.1 vs 6.2±0.1, NS), urinary Na+/creatinine (37±5 vs 41±5 mmol/mmol, NS), K+/creatinine (81±6 vs 94±7 mmol/mmol, NS), plasma Na+ (147±1 versus 147±1 mmol, NS) or plasma K+ (4.2±0.1 vs 4.4±0.1 mmol, NS). In conclusion, we successfully generated TAL‐specific NHE3 knockout mouse and found that NHE3 in the TAL contributes to urinary concentrating ability and acid‐base regulation. This mouse model will further be useful to delineate the TAL‐specific role of NHE3 for renal function.Support or Funding InformationTR is supported by the National Institute of Diabetes and Digestive and Kidney Diseases (1R01DK110621) and American Heart Association Transformational Research Award (19TPA34850116), LT was supported by an American Heart Association Postdoctoral Fellowship (19POST34400026) and JX was supported by an American Heart Association Predoctoral Fellowship (18PRE33990236).

Cisplatin Decreases ENaC Activity Contributing to Renal Sodium Wasting

Cisplatin (CDDP) is a platinum‐containing compound that has antineoplastic effects due to its ability to bind DNA and inhibit replication. While an important chemotherapy drug, CDDP results in a renal salt and water‐wasting syndrome and is nephrotoxic. The origin of the renal salt and water‐wasting caused by CDDP is obscure; though, some evidence suggests that broad inhibition of the Na+/K+‐ATPase by CDDP results in generalized decreases in tubular reabsorption causing increases in sodium and water excretion. The effects of CDDP on the epithelial Na+ channel (ENaC), which is the final arbiter of renal Na+ excretion, are unknown. We test here if CDDP affects the activity of ENaC to influence renal salt and water excretion. These studies focus on understanding the cellular mechanism by which CDDP may affect ENaC. For these studies, C57Bl/6 male mice were randomly divided into 3 groups, as follow: 1) Saline, 2) CDDP and 3) Benzamil (BZM) treated. For metabolic cages experiments, C57Bl/6 male mice received a Na+ load (100 μL of a 0.9% NaCl solution) and were treated with CDDP (25 mg/kg, i.p.) or BZM (1.4 mg/kg, i.p.). Then, water consumption, Na+ intake, urine volume, urinary Na+ and creatine excretion were evaluated every 2 h over a 10 h period. To directly quantify ENaC activity in these animals, principal cells were patch‐clamped in split‐open tubules using the cell‐attached configuration. After recording baseline ENaC activity for 5 min in these tubules, they were treated with CDDP (0.5 to 1.5 μM) with ENaC activity quantified in the presence of this drug over the next 5 min. Preliminary results show that CDDP increases excretion of a Na+ load, increases fractional excretion of sodium (FeNa) and decreases ENaC activity in isolated tubules. Importantly, our studies show that, unlike ouabain, CDDP does not affect channel conductance in cell‐attached patches. Such observations are most consistent with CDDP not affecting the electrochemical forces driving Na+ transport across principal cells, which would change in response to changes in pump activity, but rather decreasing ENaC activity through direct effects on the channel or a channel regulator. In conclusion, these observations are consistent with CDDP actions on ENaC, independent of effects on the pump, contributing to the renal salt and water wasting caused by this chemotherapy drug.Support or Funding InformationThis research was supported by NIH/NIDDK grants R01DK113816 and R01DK117909.

Renomedullary Interstitial Cell Endothelin A Receptors Regulated Blood Pressure and Renal Function

Renomedullary interstitial cells (RMIC) may modulate blood pressure (BP) and renal function through release of natriuretic factors and through direct effects on medullary blood flow (RMIC encircle vasa recta). Endothelin‐1 (ET‐1) modulates RMIC vasoactive factor release and contraction via ETA receptors (ETAR) in vitro. Consequently, we tested the hypothesis that knockout of ETAR in RMIC regulates renal function and BP in vivo. We bred ETARf/f mice containing loxP‐flanked exons 6–8 of the EDNRA gene with tamoxifen‐inducible tenascin‐C‐CreER2 knockin mice. Tenascin‐C‐CreER2:ETARf/f mice were injected with tamoxifen (160 mg/kg IP) for 5 consecutive days at 3 months of age to obtain RMIC ETAR KO. Littermates of the same genotype without injection served as controls. EDNRA gene recombination occurred in inner medulla, but not cortex. Inner medulla ETAR mRNA content fell by 80%, while ETBR mRNA levels were unaffected. ETRA KO did not affect BP in mice on normal (0.3% Na+) or low (0.03% Na+) salt diets. In contrast, ETAR KO reduced salt‐sensitive systolic BP elevation in mice on a high (3.2% Na+) salt diet (ETAR KO 127±3 vs. control 134±2 mmHg, n=13, 15, p&lt;0.05). Urine volume and urinary Na+ and K+ excretion were higher in high‐salt diet‐treated ETAR KO mice compared with controls during the first 3 days of high salt intake. Urinary ET‐1, nitrite/nitrate, and prostaglandin E2 excretion were increased in high salt diet‐treated ETAR KO mice vs. controls. No significant differences were found in GFR, vasopressin, aldosterone, or renin levels between high salt fed ETAR KO and control mice. Inner medullary protein and mRNA levels of total NKCC2 and ENaC‐α and ‐β were decreased, and inner medullary cyclooxygenase‐2 (COX‐2), but not COX‐1, protein levels were increased, in high salt fed ETAR KO vs. control mice (n=8). Exogenous ET‐1 did not detectably alter RMIC intracellular Ca2+ concentration or cause RMIC contraction as assessed by ex vivo inner medulla confocal imaging. We conclude that disruption of RMIC ETAR reduces salt‐sensitive hypertension and this is associated with reductions in NKCC2 and ENaC together with elevations in several autocrine and paracrine natriuretic factors. These effects of RMIC ETAR, at least based on ex vivo studies, may not involve RMIC contraction. While further study is required, our data suggest a novel regulatory pathway for maintaining water/electrolyte homeostasis.Support or Funding InformationNHLBI P01 HL136267

The Role of AT1a Receptors in Angiotensin II‐induced Hypertension: No Clear Sex Differences in The Pressor Response to Angiotensin II in Male and Female Wild‐type and Proximal Tubule‐specific AT1a Receptor Knockout Mice

Hypertension is the most important risk factor for cardiovascular, stroke, and end‐stage kidney diseases, but the mechanisms of hypertension remain incompletely understood. We reason that inappropriate activation or dysregulation of the intratubular renin‐angiotensin system in the kidney may be one of key factors in hypertension. In the present study, we generated mutant mice with proximal tubule‐specific knockout of angiotensin II (Ang II) AT1a receptors (PT‐Agtr1a−/−) in the kidney to determine whether there are significant sex differences in the pressor and natriuretic responses to Ang II. Six groups (n=8 per group) of adult male and female wild‐type and PT‐Agtr1a−/− mice were infused with Ang II via osmotic minipump for 2 weeks (40 ng/min, i.p.), and concurrently treated with or without the AT1 receptor blocker losartan (20 mg/kg/day, p.o.) to study the roles of extrarenal and proximal tubule AT1a receptors. Basal systolic blood pressure was approximately13 ± 3 mmHg lower in male and female PT‐Agtr1a−/− mice than wild‐type controls (P&lt;0.01). Basal 24 h urinary Na+ (UNaV), K+ (UKV), and Cl− excretion (UCl−V) were all significantly higher in male and female PT‐Agtr1a−/− mice than wild‐type controls (P&lt;0.01). In response to Ang II infusion, both male and female wild‐type and PT‐Agtr1a−/− mice developed time‐dependent hypertension, and the magnitudes of the pressor response were similar between wild‐type male (Δ43 ± 3 mmHg, P&lt;0.01) and female (Δ44 ± 3 mmHg, P&lt;0.01), and between male (Δ43 ± 3 mmHg, P&lt;0.01) and female PT‐Agtr1a−/− mice (Δ39 ± 5 mmHg, P&lt;0.01). In male wild‐type mice, 24 h UNaV increased from 139.3 ± 22.3 μmol/24 h in the time‐control group to 196.4 ± 29.6 μmol/24 h in the Ang II‐infused group (P&lt;0.05). In female wild‐type mice, 24 h UNaV increased from 102.3 ± 12.3 μmol/24 h in the time‐control group to 173.2 ± 19.1 μmol/24 h in the Ang II‐infused group (P&lt;0.05), respectively. In male PT‐Agtr1a−/− mice, 24 h UNaV increased from 172.0 ± 10.2 μmol/24 h in the time‐control group to 264.7 ± 35.4 μmol/24 h in the Ang II‐infused group (P&lt;0.05). In female PT‐Agtr1a−/− mice, 24 h UNaV increased from 106.5 ± 15.0 μmol/24 h in the time‐control group to 169.1 ± 21.9 μmol/24 h in the Ang II‐infused group (P&lt;0.05), respectively. The pressor responses to Ang II was attenuated, while the natriuretic response was promoted by concurrent treatment with losartan in male and female wild‐type and PT‐Agtr1a−/− mice (P&lt;0.05). Taken together, we demonstrate that intratubular Ang II and AT1a receptors in the proximal tubules play a key role in maintaining normal blood pressure homeostasis and body salt and fluid balance, and that there are no significant sex differences in the pressor and natriuretic responses to Ang II in wild‐type and PT‐Agtr1a−/− mice.Support or Funding InformationThis work was supported by NIDDK grants, 2R01DK067299‐10A1 and 2R01DK102429‐03A1 to Dr. Zhuo.

Sodium and Potassium Intakes and Their Ratio in Adults (18-90 y): Findings from the Irish National Adult Nutrition Survey.

An individual’s sodium to potassium intake ratio (Na:K) has been shown to be an important predictor of hypertension. The aim of this study was to estimate the mean 24 h urinary Na, K and Na:K of Irish adults and to identify the foods that determine Na:K in a nationally representative sample of Irish adults. This study was based on data from the Irish National Adult Nutrition Survey (2008–2010) (NANS), which collected spot urine samples and dietary data in a nationally representative sample of Irish adults aged 18+ years. The mean urinary molar Na:K of Irish men and women was 1.90 and 2.15, respectively, which exceed target molar ratios of ≤1.0 and ≤2.0. The mean estimated 24-h urinary excretion of Na was 4631 mg for men and 3525 mg for women, which exceed target maximum population intakes for all gender and age groups. The mean estimated 24-h urinary excretion of K was 3894 mg for men and 2686 mg for women, with intakes in women of all ages and older men (65+ years) below current recommendations. The key foods positively associated with a lower Na:K were fruits, vegetables, potatoes, breakfast cereals, milk, yogurt and fresh meat, while the foods negatively associated with a lower Na:K were breads, cured and processed meats and butters and fat spreads. Strategies to reduce sodium and increase potassium intakes are necessary to lower population Na:K, which may help to reduce the burden of hypertension-related diseases in the Irish population.

Increased Aortic Characteristic Impedance Explains Relations Between Urinary Na+/K+ and Pulse or Systolic Blood Pressure.

Alterations in sodium (Na+) relative to potassium (K+) intake increase systolic blood pressure, effects in-part attributed to enhanced pulsatile loads (pulse pressure) beyond steady-state pressures (mean arterial pressure). Whether this effect is through reversible changes (increases in blood volume and hence aortic flow [Q] or wave reflection [Pb]), or potentially irreversible structural changes in the proximal aorta, is unknown. In 581 black South Africans, we determined 24-hour urinary Na+ and K+ excretion and aortic function from central aortic pressure (radial pulse wave analysis [SphygmoCor software]), velocity, and diameter measurements. Proximal aortic function was assessed from characteristic impedance (Zc). Beyond mean arterial pressure and additional confounders, urinary Na+/K+ was independently associated with Zc (P<0.005) but not peak aortic Q (P=0.30) or alternative aspects of Q or ejection volume. Although age was strongly associated with proximal aortic diameter, no independent relations between urinary Na+/K+ and aortic diameter were noted (P=0.17). Relations between urinary Na+/K+ and Zc translated into independent relations with early systolic compression wave pressures (QxZc [PQxZc]) and aortic forward wave pressures but not Pb. Moreover, neither reflected wave magnitude (P=0.92) nor aortic pulse wave velocity were independently associated with urinary Na+/K+. In product of coefficient mediation analysis, the independent relations between urinary Na+/K+ and peak aortic or brachial pulse pressure or systolic blood pressure were accounted for by Zc and PQxZc. In conclusion, abnormalities in Na+/K+ intake determine pulse pressure or systolic blood pressure beyond mean arterial pressure mainly through potentially irreversible impacts on proximal aortic impedance rather than readily modifiable increases in aortic flow (blood volume) or wave reflection.