Effects of sodium intake, age, gender, blood sampling time on distribution of plasma aldosterone, renin activity, deoxycorticosterone, cortisol, cortisone, and 24 h urinary aldosterone levels in normotensive individuals based on LC-MS/MS.

PURPOSE: This study aims to analyze the distribution of plasma aldosterone, renin activity, deoxycorticosterone (DOC), cortisol, cortisone, and 24 h urinary aldosterone (24 h-uAld) levels based on liquid chromatography-tandem mass spectrometry (LC-MS/MS) method. MATERIALS AND METHODS: Plasma and 24 h urine were collected from 129 healthy volunteers in Northeast China. The effect of sodium intake, age, gender, blood sampling time on plasma aldosterone concentration (PAC), plasma renin activity (PRA), PAC to PRA ratio (ARR), DOC, cortisol, cortisone, cortisol to cortisone ratio, and 24 h-uAld were investigated by nonparametric test, multiple linear regression and Harris-Boyd's standard deviate test. RESULTS: There was no significant difference observed in 24 h-uAld, PAC (AM), PRA(AM), ARR (AM), DOC (AM), cortisol (AM), cortisone (AM), and cortisol to cortisone (AM) between high and low sodium intake group. Significant differences were observed between morning and afternoon sampling groups in terms of PAC, ARR, DOC, cortisol, and cortisone. Reference intervals (RIs) of 24 h-uAld, PAC (AM) were recommended to be partitioned by gender. RI of PRA was recommended age stratification. CONCLUSION: We recommend that the same reference interval could be used regardless of sodium intake. Gender is the main influence factor for 24 h-uAld, PAC, and ARR. Age is key influence factor for PRA.

A LC-MS/MS method for the simultaneous quantitative determination of aldosterone, its precursor 18-hydroxycorticosterone and its metabolite tetrahydroaldosterone in human urine.

Aldosterone (ALD), its precursor 18-hydroxycorticosterone (18-OHB) and its metabolite tetrahydroaldosterone (TH-ALD) are important biomarkers for the diagnosis of primary aldosteronism (PA). Liquid chromatography-tandem mass spectrometry (LC-MS/MS) is increasingly utilized in the detection of small molecules of hormones because it has advantages in terms of specificity and sensitivity. The objective of this study is to develop a new LC-MS/MS method for the simultaneous quantification of ALD (free), 18-OHB, and TH-ALD in human urine and attempt to diagnose primary aldosteronism using different indicators. The urine samples were treated with a solid-phase extraction pretreatment technique and the three analytes were separated on a reversed-phase column and detected on a triple quadrupole mass spectrometer. The established method was validated according to CLSI C62-A standard guidelines. The calibration ranges from 25 pg/mL to 5000 pg/mL for aldosterone (free), 18-hydroxycorticosterone and tetrahydroaldosterone, and the lower limit of quantification for these three analytes was 25 pg/mL. The matrix effects and recoveries of these three analytes ranged from 85.1 % to 115 % and from 86.3 % to 114 %, respectively. The intra-day and inter-day precision ranged from 1.29 % to 6.78 % and from 1.77 % to 8.64 %, respectively. The performance of the method met the requirements of the guidelines. 40 clinical urine samples including 22 PA patients and 18 non-PA patients were detected, and the ROC curves of three diagnostic indicators were established. The area under the curve (AUC) of ALD (free) is the biggest, so ALD (free) was the best compound to be used as a diagnostic indicator in this study. When the cut-off point was taken as 141 ng/24-h, the sensitivity was 72.7 % and the specificity was 88.9 %. We developed and validated an LC-MS/MS method for the simultaneous quantification of ALD (free), 18-OHB and TH-ALD in human urine. Our study provides a reference for the use of new biomarkers for the diagnosis of primary aldosteronism.

Reference intervals for LC-MS /MS measurements of plasma renin activity, aldosterone, angiotensin II, and 24-hour urinary aldosterone in Northern Chinese Han population.

BACKGROUND: Examination of aldosterone to Renin Ratio (ARR) and plasma aldosterone concentration (PAC) or 24-h urinary aldosterone excretion (24-h UALD) was the necessary tests in confirmatory tests for primary aldosteronism (PA). We developed a combined liquid chromatography-tandem mass spectrometry method (LC-MS/MS) for plasma renin activity (PRA), PAC, and angiotensin II (Ang II) and investigated their reference intervals (RIs) in northern Chinese Han population. The RIs of 24-h UALD excretion were also studied using LC-MS/MS. METHODS: A total of 309 healthy volunteers were recruited in 3 cities in China. PRA, PAC, Ang II, and 24-h UALD were measured using the laboratory-developed LC-MS/MS. Multiple linear regression and the variance component model were applied to determine if the RI needed to be split. The RIs of PRA, PAC, and Ang II were determined using the nonparametric percentile method. RESULTS: The laboratory-developed LC-MS/MS method was verified and showed good performance. Standard deviation ratio (SDR) sex for PAC and SDR region for Ang II are 0.466 and 0.407, respectively, indicating that the RIs of PAC and Ang II must be divided by sex and region, respectively. In addition, the SDR 24hUK for 24-h UALD is 0.579, indicating that the RI of 24-h UALD must be partitioned by urine potassium. CONCLUSION: RIs were established for tests related to the renin-angiotensin-aldosterone system in the apparently healthy northern Chinese Han population by the LC-MS/MS method.

Renin-angiotensin-aldosterone system function in the pig-to-baboon kidney xenotransplantation model.

After pig-to-baboon kidney transplantation, episodes of hypovolemia and hypotension from an unexplained mechanism have been reported. This study evaluated the renin-angiotensin-aldosterone system post-kidney xenotransplantation. Kidneys from genetically-engineered pigs were transplanted into 5 immunosuppressed baboons after the excision of the native kidneys. Immunosuppressive therapy was based on the blockade of the CD40/CD154 costimulation pathway. Plasma renin, angiotensinogen (AGT), angiotensin II (Ang II), aldosterone levels, and urine osmolality and electrolytes were measured in healthy pigs, healthy nonimmunosuppressed baboons, and immunosuppressed baboons with life-supporting pig kidney grafts. After pig kidney transplantation, plasma renin and Ang II levels were not significantly different, although Ang II trended lower, even though plasma AGT and potassium were increased. Plasma aldosterone levels were unchanged. Urine osmolality and sodium concentration were decreased. Even in the presence of increasing AGT and potassium levels, lower plasma Ang II concentrations may be because of reduced, albeit not absent, the reactivity of pig renin to cleave baboon AGT, suggesting an impaired response of the renin-angiotensin-aldosterone system to hypovolemic and hypotensive episodes. The maintenance of aldosterone may be protective. The reduced urine osmolality and sodium concentration reflect the decreased ability of the pig kidney to concentrate urine. These considerations should not prohibit successful clinical pig kidney xenotransplantation.

Urinary tetrahydroaldosterone is associated with circulating FGF23 in kidney stone formers.

The spectrum of diseases with overactive renin-angiotensin-aldosterone system (RAS) or elevated circulating FGF23 overlaps, but the relationship between aldosterone and FGF23 remains unclarified. Here, we report that systemic RAS activation sensitively assessed by urinary tetrahydroaldosterone excretion is associated with circulating C-terminal FGF23. We performed a retrospective analysis in the Bern Kidney Stone Registry, a single-center observational cohort of kidney stone formers. Urinary excretion of the main aldosterone metabolite tetrahydroaldosterone was measured by gas chromatography-mass spectrometry. Plasma FGF23 concentrations were measured using a C-terminal assay. Regression models were calculated to assess the association of plasma FGF23 with 24 h urinary tetrahydroaldosterone excretion. We included 625 participants in the analysis. Mean age was 47 ± 14 years and 71% were male. Mean estimated GFR was 94 ml/min per 1.73 m2. In unadjusted analyses, we found a positive association between plasma FGF23 and 24 h urinary tetrahydroaldosterone excretion (ß: 0.0027; p = 4.2 × 10-7). In multivariable regression models adjusting for age, sex, body mass index and GFR, this association remained robust (ß: 0.0022; p = 2.1 × 10-5). Mineralotropic hormones, 24 h urinary sodium and potassium excretion as surrogates for sodium and potassium intake or antihypertensive drugs did not affect this association. Our data reveal a robust association of RAS activity with circulating FGF23 levels in kidney stone formers. These findings are in line with previous studies in rodents and suggest a physiological link between RAS system activation and FGF23 secretion.

Hepatocellular carcinoma induces body mass loss in parallel with osmolyte and water retention in rats.

AIMS: The number of cancer survivors with cardiovascular disease is increasing. However, the effect of cancer on body fluid regulation remains to be clarified. In this study, we evaluated body osmolyte and water imbalance in rats with hepatocellular carcinoma. MAIN METHODS: Wistar rats were administered diethylnitrosamine, a carcinogenic drug, to establish liver cancer. We analyzed tissue osmolyte and water content, and their associations with aldosterone secretion. KEY FINDINGS: Hepatocellular carcinoma rats had significantly reduced body mass and the amount of total body sodium, potassium, and water. However, these rats had significantly increased relative tissue sodium, potassium, and water content per tissue dry weight. Furthermore, these changes in sodium and water balance in hepatocellular carcinoma rats were significantly associated with increased 24-h urinary aldosterone excretion. Supplementation with 0.25% salt in drinking water improved body weight reduction associated with sodium and water retention in hepatocellular carcinoma rats, which was suppressed by treatment with spironolactone, a mineralocorticoid receptor antagonist. Additionally, the urea-driven water conservation system was activated in hepatocellular carcinoma rats. SIGNIFICANCE: These findings suggest that hepatocellular carcinoma induces body mass loss in parallel with activation of the water conservation system including aldosterone secretion and urea accumulation to retain osmolyte and water. The osmolyte and water retention at the tissue level may be a causative factor for ascites and edema formation in liver failure rats.

Aldosterone suppresses cardiac mitochondria.

Elevated serum aldosterone promotes arterial hypertension, cardiac hypertrophy, and diastolic dysfunction. However, the effect of elevated aldosterone levels on cardiac mitochondria remains unclear. We used primary cultures of mouse cardiomyocytes to determine whether aldosterone has direct effects on cardiomyocyte mitochondria, and aldosterone-infused mice as a preclinical model to evaluate the impact of aldosterone in vivo. We show that aldosterone suppressed mtDNA copy number and SOD2 expression via the mineralocorticoid receptor (MR)-dependent regulation of NADPH oxidase 2 (NOX2) and generation of reactive oxygen species (ROS) in primary mouse cardiomyocytes. Aldosterone suppressed cardiac mitochondria adenosine triphosphate production, which was rescued by N-acetylcysteine. Aldosterone infusion for 4 weeks in mice suppressed the number of cardiac mitochondria, mtDNA copy number, and SOD2 protein expression. MR blockade by eplerenone or the administration of N-acetylcysteine prevented aldosterone-induced cardiac mitochondrial damage in vivo. Similarly, patients with primary aldosteronism had a lower plasma leukocyte mtDNA copy number. Plasma leukocyte mtDNA copy number was positively correlated with 24-hour urinary aldosterone level and left ventricular mass index. In conclusion, aldosterone suppresses cardiac mitochondria in vivo and directly via MR activation of ROS pathways.

First-in-Human Study of MANP: A Novel ANP (Atrial Natriuretic Peptide) Analog in Human Hypertension.

[Figure: see text].

Clinical Utility of the Ratio of Urinary Free Cortisol to Aldosterone as an Index for Inflammatory and Metabolic Dysregulation.

OBJECTIVE: Urinary free cortisol (UFC) is a reliable marker to avoid cortisol fluctuation and the effects of binding proteins. However, UFC levels are affected by fluid intake and urine volume, and the normal levels range widely. METHODS: To discover the utility of the ratio of urinary cortisol to aldosterone excretions, 246 patients in whom daily excretions of UFC and aldosterone (UAC) were measured were retrospectively analyzed. RESULTS: The UFC/UAC ratio showed significant positive and negative correlations with the levels of serum cortisol (R=0.287) and aldosterone (R=-0.762), respectively. The UFC/UAC ratio increased with aging in female patients, while it was not altered by the level of BMI in either gender. Markers for metabolic and inflammatory status, including hemoglobin A1c (R=0.327), albumin (R=-0.331), C-reactive protein (R=0.317), ferritin (R=0.473), and D-dimer (R=0.569), showed correlations with the ratio of UFC/UAC that were more significant than the correlations with the serum level of cortisol or UFC alone. Of note, the UFC/UAC ratio was shown to be an indicator for the risk of diabetes (AUC: 0.765), hypoalbuminemia (0.839), hyper-CRPemia (0.748), and thrombophilia (0.824), in which the cut-off levels of the UFC/UAC ratio were around 12. CONCLUSION: The UFC/UAC ratio is a variable for detecting metabolic and inflammatory complications related to adrenocortical dysfunction.

Factors affecting the urinary aldosterone-to-creatinine ratio in healthy dogs and dogs with naturally occurring myxomatous mitral valve disease.

BACKGROUND: Chronic renin-angiotensin-aldosterone system (RAAS) activation in course of heart diseases contributes to cardiac remodeling and heart failure. Myxomatous mitral valve disease (MMVD) is characterized by different stages of severity and trend of RAAS activity during the course of the disease is still uncertain. The urinary aldosterone-to-creatinine ratio (UAldo:C) has been proven to reflect RAAS activation in dogs and might be a useful marker in monitoring therapy and disease progression, but data about this parameter need to be expanded. The objective of this study was to evaluate the UAldo:C in healthy dogs and dogs with naturally occurring MMVD, and to investigate the relationships between this parameter and clinical, echocardiographic and laboratory variables. RESULTS: The study population consisted of 149 dogs: 49 healthy and 100 MMVD dogs (45 stage B1, 13 stage B2 and 42 stage C). Urinary aldosterone-to-creatinine ratio was not significantly different among healthy and MMVD dogs of any stages. Breed, sex and age showed a significant impact on UAldo:C. In particular, Chihuahua and Cavalier King Charles spaniel showed significantly higher UAldo:C than other breeds, as well as intact females than other genders. In stage C dogs, UAldo:C appeared to be increased by spironolactone and was positively associated with furosemide dose (P = 0.024). Aldosterone breakthrough (ABT) appeared to occur in 36% (8/22) of stage C dogs not receiving spironolactone. A significant positive association between UAldo:C and left atrium-to-aortic root ratio (LA/Ao) was found. CONCLUSIONS: Individual factors such as breed, sex and age appeared to influence UAldo:C, and therapy seemed to add further variability. In the light of these results, comparing the UAldo:C of a single patient with a population-based reference value might lead to wrong interpretations and an individual monitoring should be considered. The prevalence of ABT in the present study (36%) was in line with those previously reported. However, due to the high individual variability of UAldo:C found in the study, even this result should be re-evaluated in the setting of an individual longitudinal approach. The positive association between UAldo:C and LA/Ao supports the mutual relationship between RAAS and cardiac remodeling.

Paradoxical Increase of 24-Hour Urinary Aldosterone Levels in Obese Patients With Resistant Hypertension on a High Salt Diet.

BACKGROUND: Having previously reported that aldosterone levels increase progressively with body mass index (BMI), the current analysis was done to determine to what extent this association is related to dietary high salt intake. We anticipated that aldosterone levels would decrease with higher sodium status consistent with classical suppression of aldosterone release secondary to progressive fluid retention induced by high dietary sodium intake. METHODS: Cross-sectional analysis of a large diverse cohort of 2,705 patients with resistant hypertension (HTN) seen in a referral HTN Clinic. Dietary sodium intake was indexed by 24-hour (h) urinary sodium (UNa), aldosterone status was determined by plasma aldosterone concentration, plasma renin activity, and 24 h urinary aldosterone (UAldo). Patients with normal weight served as control. RESULTS: In this study, 1,572 individuals with complete 24 h urine collections were analyzed. Mean BMI was 32.5 ± 7.1 kg/m2 and ranged from 24.6 ± 2.4 kg/m2 (first quartile) to 41.0 ± 4.2 kg/m2 (fourth quartile). BMI was positively associated with 24 h UNa and UAldo levels (P < 0.0001), 24 h UNa and UAldo. There was a positively stronger correlation in obese (r = 0.273, P < 0.0001) compared with normal weight individuals (r = 0.108, P = 0.0342) independent of number and classes of antihypertensive medications. CONCLUSIONS: Our analysis shows that there is an altered regulation of aldosterone in obese patients in the setting of high dietary salt intake.

Masked Uncontrolled Hypertension Is Accompanied by Increased Out-of-Clinic Aldosterone Secretion.

Masked uncontrolled hypertension (MUCH) in treated patients is defined as controlled office blood pressure (BP) but uncontrolled out-of-clinic ambulatory BP. Previously, we have shown that patients with MUCH have evidence of heightened out-of-clinic sympathetic nervous system activity. The aim is to test the hypothesis that MUCH patients have higher aldosterone secretion compared with patients with true controlled hypertension. Two hundred twenty-two patients were recruited after having controlled office BP readings at ≥3 clinic visits. Patients taking MR (mineralocorticoid receptor) antagonists and epithelial sodium channel blockers were excluded. All patients were evaluated by clinic automated office BP and morning serum aldosterone and plasma renin activity. Out-of-clinic ambulatory BP monitoring and 24-hour urinary aldosterone, catecholamines, and metanephrines were also measured. Sixty-four patients had MUCH, and the remaining 48 patients had true controlled hypertension. MUCH patients had significantly higher out-of-clinic levels of 24-hour urinary aldosterone, catecholamines, and metanephrines compared with true controlled hypertension. The 2 groups did not differ in serum aldosterone, plasma renin activity, or aldosterone-renin ratio collected in clinic. In addition, 32.8% of MUCH patients had high out-of-clinic 24-hour urinary aldosterone (≥12 µg) but normal clinic serum aldosterone (<15 ng/dL) and aldosterone-renin ratio (<20). Further, in correlation matrix analysis, higher 24-hour urinary catecholamines and metanephrines were associated with higher 24-hour urinary aldosterone and plasma renin activity levels in MUCH patients. Patients with MUCH have higher out-of-clinic urinary aldosterone levels compared with patients with true controlled hypertension. This study suggests that patients with MUCH likely have higher out-of-clinic sympathetic nervous system tone increases aldosterone secretion mediated by increased renin release that may contribute to their higher out-of-clinic BP.

Effects of Menstrual Cycle Phase on Fluid Regulation during Walking Exercise.

To elucidate the fluid regulation in different menstrual cycle phases during exercise. Sex hormones affect fluid regulation in different ways. Moreover, the renin angiotensin-aldosterone system is activated in the luteal phase in rest. However, there are limited studies on fluid regulation affected by such hormone excretion in the menstrual cycle during exercise, especially during a light walking exercise. A non-invasive method using urine samples to determine menstrual cycle phases was used, and the follicular and luteal phases were successfully confirmed in 10 participants (age, 21 ± 1 years; body mass index, 20.5 ± 2.1 kg/m2). The experimental exercise sessions consisted of 5-min standing and 15-min walking at 2 km/h on 15% slope (approximately 8.3°) on a treadmill. Each participant carried a backpack weighing 5% of her own weight, and performed three sessions of walking exercise. Urine aldosterone excretion was significantly higher in the luteal than in the follicular phase before and after walking (p < 0.05). Urinary excretion of aldosterone was five times higher in the luteal than in the follicular phase before and after walking exercise. Heart rates during walking, after rest, and after recovery were all significantly higher in the luteal than in the follicular phase (p < 0.05). The participants' ratings of perceived exertion during the first and third session of walking in the luteal phase was not higher than that at the follicular phase. The results of our study suggested that increased activity of the renin-angiotensin-aldosterone system in the luteal phase of the menstrual cycle might be further activated during exercise. This may increase the circulatory load, which is reflected as increased heart rate. These results suggested that premenopausal women may better take into account a possibility of an increased circulatory load in the luteal phase even when they perform light exercise.

Impact of mineralocorticoid receptor blockade with direct renin inhibition in angiotensin II-dependent hypertensive mice.

It has been suggested that aldosterone breakthrough during treatment with a type 1 angiotensin II receptor (AT1R) blocker (ARB) may be an important risk factor for the progression of renal and cardiovascular disease. We examined whether the direct renin inhibitor, aliskiren caused aldosterone breakthrough in angiotensin II (Ang II)-dependent hypertensive mice. The effect of combination therapy with aliskiren and eplerenone was compared with that of therapy using renin-angiotensin system (RAS) blockade. Tsukuba hypertensive mice were treated for 12 weeks with aliskiren (30 mg/kg/day, i.p), candesartan (5 mg/kg/day, p.o), eplerenone (100 mg/kg/day, p.o) aliskiren and candesartan, aliskiren and eplerenone or candesartan and eplerenone. Blood pressure, urinary aldosterone and angiotensinogen (AGTN) excretion; plasma endothelin-1 concentration; kidney weight; urinary albumin excretion (UAE); glomerular injury; and renal messenger RNA (mRNA) levels for transforming growth factor (TGF)-ß1, plasminogen activator inhibitor (PAI)-1, angiotensin-converting enzyme (ACE) and AT1R were measured. Combination therapy with aliskiren and candesartan caused a further decrease in blood pressure (p < 0.05) compared with either agent alone. Urinary aldosterone excretion was decreased significantly by 4 weeks of treatment with aliskiren or candesartan (p < 0.05). However, it was increased again by treatment with candesartan or aliskiren for 12 weeks. Combination therapy with aliskiren and eplerenone significantly decreased UAE, the glomerulosclerosis index, and PAI-1 and TGF-ß1 mRNA levels compared with all other therapies (p < 0.05). Treatment with aliskiren decreased urinary aldosterone excretion at 4 weeks and increased it at 12 weeks. Combination therapy with a direct renin inhibitor and a mineralocorticoid receptor blocker may be effective for the prevention of renal injury in Ang II-dependent hypertension.

The Unrecognized Prevalence of Primary Aldosteronism: A Cross-sectional Study.

BACKGROUND: Primary aldosteronism is a nonsuppressible renin-independent aldosterone production that causes hypertension and cardiovascular disease. OBJECTIVE: To characterize the prevalence of nonsuppressible renin-independent aldosterone production, as well as biochemically overt primary aldosteronism, in relation to blood pressure. DESIGN: Cross-sectional study. SETTING: 4 U.S. academic medical centers. PARTICIPANTS: Participants with normotension (n = 289), stage 1 hypertension (n = 115), stage 2 hypertension (n = 203), and resistant hypertension (n = 408). MEASUREMENTS: Participants completed an oral sodium suppression test, regardless of aldosterone or renin levels, as a confirmatory diagnostic for primary aldosteronism and to quantify the magnitude of renin-independent aldosterone production. Urinary aldosterone was measured in participants in high sodium balance with suppressed renin activity. Biochemically overt primary aldosteronism was diagnosed when urinary aldosterone levels were higher than 12 µg/24 h. RESULTS: Every blood pressure category had a continuum of renin-independent aldosterone production, where greater severity of production was associated with higher blood pressure, kaliuresis, and lower serum potassium levels. Mean adjusted levels of urinary aldosterone were 6.5 µg/24 h (95% CI, 5.2 to 7.7 µg/24 h) in normotension, 7.3 µg/24 h (CI, 5.6 to 8.9 µg/24 h) in stage 1 hypertension, 9.5 µg/24 h (CI, 8.2 to 10.8 µg/24 h) in stage 2 hypertension, and 14.6 µg/24 h (CI, 12.9 to 16.2 µg/24 h) in resistant hypertension; corresponding adjusted prevalence estimates for biochemically overt primary aldosteronism were 11.3% (CI, 5.9% to 16.8%), 15.7% (CI, 8.6% to 22.9%), 21.6% (CI, 16.1% to 27.0%), and 22.0% (CI, 17.2% to 26.8%). The aldosterone-renin ratio had poor sensitivity and negative predictive value for detecting biochemically overt primary aldosteronism. LIMITATION: Prevalence estimates rely on arbitrary and conventional thresholds, and the study population may not represent nationwide demographics. CONCLUSION: The prevalence of primary aldosteronism is high and largely unrecognized. Beyond this categorical definition of primary aldosteronism, there is a prevalent continuum of renin-independent aldosterone production that parallels the severity of hypertension. These findings redefine the primary aldosteronism syndrome and implicate it in the pathogenesis of "essential" hypertension. PRIMARY FUNDING SOURCE: National Institutes of Health.

Loss of circadian gene Bmal1 in the collecting duct lowers blood pressure in male, but not female, mice.

Kidney function follows a 24-h rhythm subject to regulation by circadian genes including the transcription factor Bmal1. A high-salt diet induces a phase shift in Bmal1 expression in the renal inner medulla that is dependent on endothelin type B (ETB) receptors. Furthermore, ETB receptor-mediated natriuresis is sex dependent. Therefore, experiments tested the hypothesis that collecting duct Bmal1 regulates blood pressure in a sex-dependent manner. We generated a mouse model that lacks Bmal1 expression in the collecting duct, where ETB receptor abundance is highest. Male, but not female, collecting duct Bmal1 knockout (CDBmal1KO) mice had significantly lower 24-h mean arterial pressure (MAP) than flox controls (105 ± 2 vs. 112 ± 3 mmHg for male mice and 106 ± 1 vs. 108 ± 1 mmHg for female mice, by telemetry). After 6 days on a high-salt (4% NaCl) diet, MAP remained significantly lower in male CDBmal1KO mice than in male flox control mice (107 ± 2 vs. 113 ± 1 mmHg), with no significant differences between genotypes in female mice (108 ± 2 vs. 109 ± 1 mmHg). ETB receptor blockade for another 6 days increased MAP similarly in both male and female CDBmal1KO and flox control mice. However, MAP remained lower in male CDBmal1KO mice than in male flox control mice (124 ± 2 vs. 130 ± 2 mmHg). No significant differences were observed between female CDBmal1KO and flox mice during ETB blockade (130 ± 2 vs. 127 ± 2 mmHg). There were no significant genotype differences in amplitude or phase of MAP in either sex. These data suggest that collecting duct Bmal1 has no role in circadian MAP but plays an important role in overall blood pressure in male, but not female, mice.

NBCe1-A is required for the renal ammonia and K+ response to hypokalemia.

Hypokalemia increases ammonia excretion and decreases K+ excretion. The present study examined the role of the proximal tubule protein NBCe1-A in these responses. We studied mice with Na+-bicarbonate cotransporter electrogenic, isoform 1, splice variant A (NBCe1-A) deletion [knockout (KO) mice] and their wild-type (WT) littermates were provided either K+ control or K+-free diet. We also used tissue sections to determine the effect of extracellular ammonia on NaCl cotransporter (NCC) phosphorylation. The K+-free diet significantly increased proximal tubule NBCe1-A and ammonia excretion in WT mice, and NBCe1-A deletion blunted the ammonia excretion response. NBCe1-A deletion inhibited the ammoniagenic/ammonia recycling enzyme response in the cortical proximal tubule (PT), where NBCe1-A is present in WT mice. In the outer medulla, where NBCe1-A is not present, the PT ammonia metabolism response was accentuated by NBCe1-A deletion. KO mice developed more severe hypokalemia and had greater urinary K+ excretion during the K+-free diet than did WT mice. This was associated with blunting of the hypokalemia-induced change in NCC phosphorylation. NBCe1-A KO mice have systemic metabolic acidosis, but experimentally induced metabolic acidosis did not alter NCC phosphorylation. Although KO mice have impaired ammonia metabolism, experiments in tissue sections showed that lack of ammonia does impair NCC phosphorylation. Finally, urinary aldosterone was greater in KO mice than in WT mice, but neither expression of epithelial Na+ channel α-, ß-, and γ-subunits nor of H+-K+-ATPase α1- or α2-subunits correlated with changes in urinary K+. We conclude that NBCe1-A is critical for the effect of diet-induced hypokalemia to increase cortical proximal tubule ammonia generation and for the expected decrease in urinary K+ excretion.

Adherence to consensus guidelines for screening of primary aldosteronism in an urban healthcare system.

BACKGROUND: Primary aldosteronism is a common cause of secondary hypertension. Treatment with adrenalectomy or mineralocorticoid receptor-blockers can prevent long-term adverse outcomes. This study aimed to determine primary aldosteronism screening rats in patients with hypertension in an underserved urban healthcare system. METHODS: We reviewed records of outpatient adults in an urban healthcare system from 2013 to 2017. Chart review along with International Statistical Classification of Diseases, 9th and 10th editions, diagnosis codes were used to identify patients meeting inclusion criteria for screening according to the 2016 Endocrine Society guidelines. The corresponding aldosterone, plasma renin activity, and 24-hour urine aldosterone values were identified. Multivariate logistic regression was performed to determine positive predictors of screening. RESULTS: Of 15,511 hypertensive patients seen, 6,809 (43.8%) met criteria for screening. Blacks were the most common racial group, and Medicare and Medicaid were the most frequent insurers. The aldosterone-to-renin ratio level was checked in 86 (1.3%) patients; 22 (25.6%) had an aldosterone-to-renin ratio >20. Of the 77 patients with hypertension and incidentaloma, 14 (18.2%) had an aldosterone-to-renin ratio checked. Additional positive predictors for being screened were hypertension and hypokalemia and sustained hypertension. CONCLUSION: Screening rates for primary aldosteronism in an underserved population are low. Proper identification of primary aldosteronism in those at risk could help ameliorate long-term effects of disease.

Aldosterone rapidly activates p-PKC delta and GPR30 but suppresses p-PKC epsilon protein levels in rat kidney.

OBJECTIVES: Aldosterone rapidly enhances protein kinase C (PKC) alpha and beta1 proteins in the rat kidney. The G protein-coupled receptor 30 (GPR30)-mediated PKC pathway is involved in the inhibition of the potassium channel in HEK-239 cells. GPR30 mediates rapid actions of aldosterone in vitro. There are no reports available regarding the aldosterone action on other PKC isoforms and GPR30 proteins in vivo. The aim of the present study was to examine rapid actions of aldosterone on protein levels of phosphorylated PKC (p-PKC) delta, p-PKC epsilon, and GPR30 simultaneously in the rat kidney. METHODS: Male Wistar rats were intraperitoneally injected with normal saline solution or aldosterone (150 µg/kg body weight). After 30 minutes, abundance and immunoreactivity of p-PKC delta, p-PKC epsilon, and GPR30 were determined by Western blot analysis and immunohisto-chemistry, respectively. RESULTS: Aldosterone administration significantly increased the renal protein abundance of p-PKC delta by 80% (p<0.01) and decreased p-PKC epsilon protein by 50% (p<0.05). Aldosterone injection enhanced protein immunoreactivity of p-PKC delta but suppressed p-PKC epsilon protein intensity in both kidney cortex and medulla. Protein abundance of GPR30 was elevated by aldosterone treatment (p<0.05), whereas the immunoreactivity was obviously changed in the kidney cortex and inner medulla. Aldosterone translocated p-PKC delta and GPR30 proteins to the brush border membrane of proximal convoluted tubules. CONCLUSIONS: This is the first in vivo study simultaneously demonstrating that aldosterone administration rapidly elevates protein abundance of p-PKC delta and GPR30, while p-PKC epsilon protein is suppressed in rat kidney. The stimulation of p-PKC delta protein levels by aldosterone may be involved in the activation of GPR30.

Solving a myth: Does boric acid stabilize aldosterone in urine at typical clinical laboratory storage conditions?

Aldosterone is produced by the adrenal gland and plays an important role in blood pressure regulation and electrolyte hemostasis. Clinically, measurement of urine aldosterone provides evidence for the diagnosis of hyper- and hypo-aldosteronism. Urine specimen that is collected in consecutive 24 h is preferred, which mitigates the risk of misdiagnosis due to large diurnal variation in aldosterone secretion. Preservatives such as boric acid are routinely added to the collection containers prior to urine collection. However, little is known of the effectiveness of these preservatives on stabilizing aldosterone in urine. In the current study, we examined the stability of urine aldosterone under typical clinical laboratory storage conditions with and without the supplementation of boric acid. Our result demonstrated that the addition of boric acid is unnecessary.