TRPM7 deficiency exacerbates cardiovascular and renal damage induced by aldosterone-salt.

Hyperaldosteronism causes cardiovascular disease as well as hypomagnesemia. Mechanisms are ill-defined but dysregulation of TRPM7, a Mg2+-permeable channel/α-kinase, may be important. We examined the role of TRPM7 in aldosterone-dependent cardiovascular and renal injury by studying aldosterone-salt treated TRPM7-deficient (TRPM7+/Δkinase) mice. Plasma/tissue [Mg2+] and TRPM7 phosphorylation were reduced in vehicle-treated TRPM7+/Δkinase mice, effects recapitulated in aldosterone-salt-treated wild-type mice. Aldosterone-salt treatment exaggerated vascular dysfunction and amplified cardiovascular and renal fibrosis, with associated increased blood pressure in TRPM7+/Δkinase mice. Tissue expression of Mg2+-regulated phosphatases (PPM1A, PTEN) was downregulated and phosphorylation of Smad3, ERK1/2, and Stat1 was upregulated in aldosterone-salt TRPM7-deficient mice. Aldosterone-induced phosphorylation of pro-fibrotic signaling was increased in TRPM7+/Δkinase fibroblasts, effects ameliorated by Mg2+ supplementation. TRPM7 deficiency amplifies aldosterone-salt-induced cardiovascular remodeling and damage. We identify TRPM7 downregulation and associated hypomagnesemia as putative molecular mechanisms underlying deleterious cardiovascular and renal effects of hyperaldosteronism.

The establishment of a novel high-throughput screening system using RNA-guided genome editing to identify chemicals that suppress aldosterone synthase expression.

Aldosterone is synthesized in the adrenal by the aldosterone synthase CYP11B2. Although the control of CYP11B2 expression is important to maintain the mineral homeostasis, its overexpression induced by the depolarization-induced calcium (Ca2+) signaling activation has been reported to increase the synthesis of aldosterone in primary aldosteronism (PA). The drug against PA focused on the suppression of CYP11B2 expression has not yet been developed, since the molecular mechanism of CYP11B2 transcriptional regulation activated via Ca2+ signaling remains unclear. To address the issue, we attempted to reveal the mechanism of the transcriptional regulation of CYP11B2 using chemical screening. We generated a cell line by inserting Nanoluc gene as a reporter into CYP11B2 locus in H295R adrenocortical cells using the CRSPR/Cas9 system, and established the high-throughput screening system using the cell line. We then identified 9 compounds that inhibited the CYP11B2 expression induced by potassium-mediated depolarization from the validated compound library (3399 compounds). Particularly, tacrolimus, an inhibitor of phosphatase calcineurin, strongly suppressed the CYP11B2 expression even at 10 nM. These results suggest that the system is effective in identifying drugs that suppress the depolarization-induced CYP11B2 expression. Our screening system may therefore be a useful tool for the development of novel medicines against PA.

MicroRNA-21 ablation exacerbates aldosterone-mediated cardiac injury, remodeling, and dysfunction.

Primary aldosteronism is characterized by excess aldosterone secretion by the adrenal gland independent of the renin-angiotensin system and accounts for ~10% of hypertensive patients. Excess aldosterone causes cardiac hypertrophy, fibrosis, inflammation, and hypertension. The molecular mechanisms that trigger the onset and progression of aldosterone-mediated cardiac injury remain incompletely understood. MicroRNAs (miRNAs) are endogenous, small, noncoding RNAs that have been implicated in multiple cardiac pathologies; however, their regulation and role in aldosterone-mediated cardiac injury and dysfunction remains mostly unknown. We previously reported that microRNA-21 (miR-21) is the most upregulated miRNA by excess aldosterone in the left ventricle in a rat experimental model of primary aldosteronism. To elucidate the role of miR-21 in aldosterone-mediated cardiac injury and dysfunction, miR-21 knockout mice and their wild-type littermates were treated with aldosterone infusion and salt in the drinking water for 2 or 8 wk. miR-21 genetic ablation exacerbated aldosterone/salt-mediated cardiac hypertrophy and cardiomyocyte cross-sectional area. Furthermore, miR-21 genetic ablation increased the cardiac expression of fibrosis and inflammation markers and fetal gene program. miR-21 genetic ablation increased aldosterone/salt-mediated cardiac dysfunction but did not affect aldosterone/salt-mediated hypertension. miR-21 target gene Sprouty 2 may be implicated in the cardiac effects of miR-21 genetic ablation. Our study shows that miR-21 genetic ablation exacerbates aldosterone/salt-mediated cardiac hypertrophy, injury, and dysfunction blood pressure independently. These results suggest that miR-21 plays a protective role in the cardiac pathology triggered by excess aldosterone. Furthermore, miR-21 supplementation may be a novel therapeutic approach to abolish or mitigate excess aldosterone-mediated cardiovascular deleterious effects in primary aldosteronism.

Galectin-3 blockade inhibits cardiac inflammation and fibrosis in experimental hyperaldosteronism and hypertension.

Hypertensive cardiac remodeling is accompanied by molecular inflammation and fibrosis, 2 mechanisms that finally affect cardiac function. At cardiac level, aldosterone promotes inflammation and fibrosis, although the precise mechanisms are still unclear. Galectin-3 (Gal-3), a ß-galactoside-binding lectin, is associated with inflammation and fibrosis in the cardiovascular system. We herein investigated whether Gal-3 inhibition could block aldosterone-induced cardiac inflammation and fibrosis and its potential role in cardiac damage associated with hypertension. Aldosterone-salt-treated rats presented hypertension, cardiac inflammation, and fibrosis that were prevented by the pharmacological inhibition of Gal-3 with modified citrus pectin. Cardiac inflammation and fibrosis presented in spontaneously hypertensive rats were prevented by modified citrus pectin treatment, whereas Gal-3 blockade did not modify blood pressure levels. In the absence of blood pressure modifications, Gal-3 knockout mice were resistant to aldosterone-induced cardiac inflammation. In human cardiac fibroblasts, aldosterone increased Gal-3 expression via its mineralocorticoid receptor. Gal-3 and aldosterone enhanced proinflammatory and profibrotic markers, as well as metalloproteinase activities in human cardiac fibroblasts, effects that were not observed in Gal-3-silenced cells treated with aldosterone. In experimental hyperaldosteronism, the increase in Gal-3 expression was associated with cardiac inflammation and fibrosis, alterations that were prevented by Gal-3 blockade independently of blood pressure levels. These data suggest that Gal-3 could be a new molecular mechanism linking cardiac inflammation and fibrosis in situations with high-aldosterone levels, such as hypertension.

Human interventions to characterize novel relationships between the renin-angiotensin-aldosterone system and parathyroid hormone.

Observational studies in primary hyperaldosteronism suggest a positive relationship between aldosterone and parathyroid hormone (PTH); however, interventions to better characterize the physiological relationship between the renin-angiotensin-aldosterone system (RAAS) and PTH are needed. We evaluated the effect of individual RAAS components on PTH using 4 interventions in humans without primary hyperaldosteronism. PTH was measured before and after study (1) low-dose angiotensin II (Ang II) infusion (1 ng/kg per minute) and captopril administration (25 mg×1); study (2) high-dose Ang II infusion (3 ng/kg per minute); study (3) blinded crossover randomization to aldosterone infusion (0.7 µg/kg per hour) and vehicle; and study (4) blinded randomization to spironolactone (50 mg/daily) or placebo for 6 weeks. Infusion of Ang II at 1 ng/kg per minute acutely increased aldosterone (+148%) and PTH (+10.3%), whereas Ang II at 3 ng/kg per minute induced larger incremental changes in aldosterone (+241%) and PTH (+36%; P<0.01). Captopril acutely decreased aldosterone (-12%) and PTH (-9.7%; P<0.01). In contrast, aldosterone infusion robustly raised serum aldosterone (+892%) without modifying PTH. However, spironolactone therapy during 6 weeks modestly lowered PTH when compared with placebo (P<0.05). In vitro studies revealed the presence of Ang II type I and mineralocorticoid receptor mRNA and protein expression in normal and adenomatous human parathyroid tissues. We observed novel pleiotropic relationships between RAAS components and the regulation of PTH in individuals without primary hyperaldosteronism: the acute modulation of PTH by the RAAS seems to be mediated by Ang II, whereas the long-term influence of the RAAS on PTH may involve aldosterone. Future studies to evaluate the impact of RAAS inhibitors in treating PTH-mediated disorders are warranted.

Aldosterone receptor antagonists: current perspectives and therapies.

Aldosterone is a downstream effector of angiotensin II in the renin-angiotensin-aldosterone system and binds to the mineralocorticoid receptor. The classical view of aldosterone primarily acting at the level of the kidneys to regulate plasma potassium and intravascular volume status is being supplemented by evidence of new "off-target" effects of aldosterone in other organ systems. The genomic effects of aldosterone are well known, but there is also evidence for non-genomic effects and these recently identified effects of aldosterone have required a revision in the traditional view of aldosterone's role in human health and disease. The aim of this article is to review the biological action of aldosterone and the mineralocorticoid receptor leading to subsequent physiologic and pathophysiologic effects involving the vasculature, central nervous system, heart, and kidneys. Furthermore, we outline current evidence evaluating the use of mineralocorticoid receptor antagonists in the treatment of primary aldosteronism, primary hypertension, resistant hypertension, obstructive sleep apnea, heart failure, and chronic kidney disease.

Congestive heart failure: where homeostasis begets dyshomeostasis.

Despite today's standard of care, aimed at preventing homeostatic neurohormonal activation, one in every five patients recently hospitalized with congestive heart failure (CHF) will be readmitted within 30 days of discharge because of a recurrence of their symptoms and signs. In light of recent pathophysiological insights, it is now propitious to revisit CHF with a view toward complementary and evolving management strategies. CHF is a progressive systemic illness. Its features include: oxidative stress in diverse tissues; an immunostimulatory state with circulating proinflammatory cytokines; a wasting of soft tissues; and a resorption of bone. Its origins are rooted in homeostatic mechanisms gone awry to beget dyshomeostasis. For example, marked excretory losses of Ca2+ and Mg2+ accompany renin-angiotensin-aldosterone system activation, causing ionized hypocalcemia and hypomagnesemia that lead to secondary hyperparathyroidism with consequent bone resorption and a propensity to atraumatic fractures. Parathyroid hormone accounts for paradoxical intracellular Ca2+ overloading in diverse tissues and consequent systemic induction of oxidative stress. In cardiac myocytes and mitochondria, these events orchestrate opening of the mitochondrial permeability transition pore with an ensuing osmotic-based destruction of these organelles and resultant cardiomyocyte necrosis with myocardial scarring. Contemporaneous with Ca2+ and Mg2+ dyshomeostasis is hypozincemia and hyposelenemia, which compromise metalloenzyme-based antioxidant defenses, whereas hypovitaminosis D threatens Ca2+ stores needed to prevent secondary hyperparathyroidism. An intrinsically coupled dyshomeostasis of intracellular Ca2+ and Zn2+, representing pro-oxidant and antioxidant, respectively, is integral to regulating the mitochondrial redox state; it can be uncoupled by a Zn2+ supplement in favor of antioxidant defenses. Hence, the complementary use of nutriceuticals to nullify dyshomeostatic responses involving macro- and micronutrients should be considered. Evolving strategies with mitochondria-targeted interventions interfering with their uptake of Ca2+ or serving as selective antioxidant or mitochondrial permeability transition pore inhibitor may also prove efficacious in the overall management of CHF.

An additional child case of an aldosterone-producing adenoma with an atypical presentation of peripheral paralysis due to hypokalemia.

Aldosterone-producing adenoma, which is characterized by hypertension, hypokalemia, and elevated aldosterone levels with suppressed plasma renin activity, is a rare condition during childhood and is also potentially curable. To the best of our knowledge, nearly 25 cases of childhood aldosterone-secreting adenoma have been reported in the literature to date. Here we describe a 13-yr-old girl with primary hyperaldosteronism secondary to aldosterone-secreting adenoma. The patient was admitted to our hospital with the neuromuscular complaints of muscle weakness and inability to walk due to hypokalemia. She had been misdiagnosed as having hypokalemic periodic paralysis 2 months before admission and her symptoms had radically improved with potassium supplementation. However, her blood pressure levels had increased and her symptoms reappeared 2 days prior to being observed during hospitalization in our institution. Laboratory examinations revealed hypokalemia (2.1 mEq/l), and increased serum aldosterone levels with suppressed plasma renin activity. Abdominal ultrasonography and abdominal magnetic resonance imaging revealed left adrenal mass. Laparoscopic adrenalectomy was performed and histopathological examinations showed benign adrenal adenoma. Serum aldosterone levels and blood pressure levels returned to normal after surgical intervention. This case demonstrates the importance of a systemic evaluation including blood pressure monitorization of children with hypokalemia as intermittent hypertension episodes may be seen; cases without hypertension may be misdiagnosed as rheumatological or neurological disorders such as hypokalemic periodic paralysis, as in our case.

Oxidative stress in aldosteronism.

Congestive heart failure (CHF) is more than a failing heart and salt-avid state. Also present is a systemic illness which features oxidative stress in diverse tissues, a proinflammatory phenotype, and a wasting of soft tissue and bone. Reactive oxygen and nitrogen species contribute to this illness and the progressive nature of CHF. Aldosteronism, an integral component of the neurohormonal profile found in CHF, plays a permissive role in leading to an altered redox state. Because of augmented urinary and fecal excretion of Ca(2+) and Mg(2+) and consequent decline in plasma-ionized [Ca(2+)](o) and [Mg(2+)](o) that accompanies aldosteronism, parathyroid glands release parathyroid hormone (PTH) in an attempt to restore Ca(2+) and Mg(2+) homeostasis; this includes bone resorption. However, PTH-mediated intracellular Ca(2+) overloading, considered a Ca(2+) paradox, leads to oxidative stress. This can be prevented by: spironolactone, an aldosterone receptor antagonist that rescues urinary and fecal cation losses; parathyroidectomy; amlodipine, a Ca(2+) channel blocker; N-acetylcysteine, an antioxidant. In addition to the role played by aldosteronism in the appearance of secondary hyperparathyroidism is the chronic use of a loop diuretic, which further enhances urinary Ca(2+) and Mg(2+) excretion, and reduced Ca(2+) stores associated with hypovitaminosis D. This broader perspective of CHF and the ever increasing clinical relevance of divalent cations and oxidative stress raise the question of their potential management with macro- and micronutrients. An emerging body of evidence suggests the nutritional management of CHF offers an approach that will be complementary to today's pharmaceutical-based strategies.

Aldosteronism and a proinflammatory vascular phenotype: role of Mg2+, Ca2+, and H2O2 in peripheral blood mononuclear cells.

BACKGROUND: Chronic, inappropriate (relative to dietary Na+) elevations in circulating aldosterone, such as occur in congestive heart failure, are accompanied by a proinflammatory vascular phenotype involving the coronary and systemic vasculature. An immunostimulatory state with activated peripheral blood mononuclear cells (PBMCs) precedes this phenotype and is induced by a fall in cytosolic free [Mg2+]i and subsequent Ca2+ loading of these cells and transduced by oxidative/nitrosative stress. METHODS AND RESULTS: We sought to further validate this hypothesis in rats with aldosterone/1%NaCl treatment (ALDOST) by using several interventions as cotreatment: a Mg2+-supplemented diet; amlodipine, a CCB; and N-acetylcysteine, an antioxidant. Blood samples were obtained at weeks 1 to 4 of ALDOST to monitor [Mg2+]i, [Ca2+]I, and H2O2 production in PBMCs. Coronal ventricular sections were examined for invading inflammatory cells and 3-nitrotyrosine labeling, a marker of oxidative/nitrosative stress. In response to ALDOST and compared with untreated controls, we found an early and persistent reduction in [Mg2+]i with a subsequent rise in [Ca2+]i and H2O2 production, each of which was either attenuated or abrogated by the Mg2+-supplemented diet and by N-acetylcysteine, whereas amlodipine prevented Ca2+ loading and an altered redox state. Cotreatment with these interventions either markedly attenuated or prevented the appearance of the proinflammatory coronary vascular phenotype and the presence of 3-nitrotyrosine in invading inflammatory cells. CONCLUSIONS: We suggest that the immunostimulatory state that appears during aldosteronism and leads to a proinflammatory coronary vascular phenotype is induced by a fall in [Mg2+]i with Ca2+ loading of PBMCs and is transduced by H2O2 production in these cells.

A case of pseudoaldosteronism, accompanied with hypocalcemia and exaggerated ACTH response.

Glycyrrhizic acid (GA) inhibits the activity of 11beta-hydroxysteroid dehydrogenase type 2 in the kidney, with the resulting increase in intrarenal cortisol concentration leading to hypertension and suppression of the renin-aldosterone system. In this paper we describe an interesting case of pseudoaldosteronism, associated with hypocalcemia and an exaggerated ACTH response. A 72-year-old woman was referred to our department for further evaluation of hypokalemia and hypocalcemia. The patient had been taking GA (150 mg/day) for the previous year for treatment of liver damage. Plasma renin activity and aldosterone concentration were both within lower normal limits. Urinary excretion of potassium and calcium was within the upper limit of the normal range and increased with administration of supplements. Plasma ACTH levels increased markedly in response to an intravenous injection of CRH. Cessation of GA and the potassium and calcium supplements on admission, led to a gradual normalization of serum potassium and calcium levels and blood pressure. The hypocalcaemia in our patient was related to decreased tubular reabsorption of calcium as a consequence of renal corticoid excess. It is possible that an increase in the number of CRH receptors in the pituitary following GA treatment caused the exaggerated ACTH response in association with pseudoaldosteronism. The existence of hypocalcemia and an exaggerated ACTH response should be observed carefully when managing pseudoaldosteronism.

[Effect of insulin in hypertension with high and low levels of renin]. / Pusobení inzulinu u vysokoreninových a nízkoreninových hypertenzí.

BACKGROUND: Setback in insulin resistance has been described in patients with essential hypertension. The aim of our study was to verify at the receptor and postreceptor levels the presence of insulin resistance in patients with high or low renin activity. METHODS AND RESULTS: Six patients with the renal artery stenosis (20 to 65 years, average age was 51 +/- 12 years, BMI: 27 +/- 2.0 kg.m2) and six patients with primary hyperaldosteronism (28 to 61 years, average age was 50 +/- 13 years, BMI: 26.9 +/- 3.2 kg.m2) were investigated. Their diagnose was confirmed by laboratory examination, computer tomography, and duplex sonography. Blood pressure was monitored for 24 hours with Spacelab tonometer (SBP: 161 +/- 29 mmHg, DBP: 98 +/- 12 mmHg versus SBP: 168 +/- 21 mmHg, DBP: 103 +/- 9 mmHg; plasma renin activity was 8.1 +/- 5.6 versus 0.3 +/- 0.4 ng.ml-1.h-1, p < 0.001; recumbent plasma aldosterone level was 98 +/- 31 versus 358 +/- 103 pg.ml-1, p < 0.001, normal value till 150 pg/ml, serum potassium was 3.9 +/- 0.4 and 3.5 +/- 0.6 mmol/l). All patients had normal course of the oral glucose tolerance test. Six volunteers of corresponding age and BMI formed the control group. Patients had normal values of the basal morning glycemia (4.9 +/- 0.5 and 5.0 +/- 0.6 versus 4.9 +/- 0.6 mmol/l), basal insulinemia level was 28.8 +/- 12.4 and 21.0 +/- 10.2 versus 15.9 +/- 8.8 mU.l-1 in healthy controls. Insulin effect was tested using isoglycemic hyperinsulinemic clamp method on Biostator with insulin infusion of 1 mU.kg.min-1. Plasma potassium concentration was kept at constant physiological levels using linear infusion pump (in patients with primary hyperaldosteronism after the prior supplementation). In patients with high-renin or low-renin hypertension, the glucose consumption during clamping was lower than that of healthy controls (M, glucose disposal rate: 23.7 +/- 4.8 and 19.5 +/- 3.4 versus 33.0 +/- 5.7 mumol.kg.-1.min-1, p < 0.001), increase of the metabolic glucose clearance (MCRG: 5.1 +/- 1.5 and 3.9 +/- 0.7 versus 7.9 +/- 1.4 ml.kg-1.min-1, p < 0.001) and tissue insulin sensitivity index (M/I: 24.3 +/- 10.1 and 26.4 +/- 8.3 versus 38.4 +/- 10.1 mumol.kg-1.min-1 to mU.l-1 x 100, p < 0.001). CONCLUSIONS: Patients with high-renin and low-renin hypertension have the insulin effectiveness significantly impaired. Such insulin resistance probably does not depend on the renin activity, plasma aldosterone concentration or on serum potassium level. The ethiopathogenesis of the described changes will be the aim of our next study.

[The effect of insulin in primary hyperaldosteronism]. / Pusobení inzulinu u primárního hyperaldosteronismu.

BACKGROUND: Deteriorated insulin resistance was described in patients with essential hypertension. The objective of the present study was to test at the receptor and postreceptor level the presence of insulin resistance in hypertension with primary hyperaldosteronism. METHODS AND RESULTS: The diagnosis of primary hyperaldosteronism was assessed by means of biochemical and imaging methods in 123 hypertensive patients with a normal glucose tolerance (mean age 49.8 +/- 12.9 years, range 20-65 years, BMI 28.3 +/- 4.8 kg/m2). The blood pressure was monitored for 24 hours by a Spacelab tonometer (systolic BP 168 +/- 21 mm Hg, diastolic BP 103 +/- 9 mm Hg, plasma aldosterone in a recumbent position 426 +/- 472 pg/ml (normal values under 150 pg/ml), concentration of serum potassium 3.6 +/- 0.6 mmol/l. The control group was formed by seven volunteers matched for age and BMI. The patients had a normal basal blood sugar level in the morning (5.0 +/- 0.6 mmol/l), the basal insulinaemia was 19.5 +/- 10.2 mU/l. The insulin resistance was examined using the method of an euglycaemic hyperinsulinaemic clamp on Biostator at an insulin infusion rate of 1 mU/kg/min. Concurrently insulin receptors on red blood cells were assessed. The plasma potassium concentration was maintained by means of insulin receptors on erythrocytes. The potassium plasma concentration was maintained by means of a linear dosage device with potassium at constant physiological levels (after previous supplementation). In patients with primary hyperaldosteronism the authors observed, as compared with healthy controls, a lower glucose consumption during the clamping (glucose disposal rate 18.7 +/- 4.8 vs 29.3 +/- 3.7 mumol/kg/min, p < 0.01), a rise of the metabolic glucose clearance (3.8 +/- 1.5 vs. 7.0 +/- 1.1 ml/kg/min, p < 0.01 and an index of tissue sensitivity for insulin) 23.7 +/- 9.8 vs. 37.5 +/- 11.6 mumol/kg/min per mU/l x 100, p < 0.02). The characteristics of insulin receptors in patients with primary hyperaldosteronism did not differ from normal values. No correlation was found between the plasma concentration of aldosterone and the index of tissue sensitivity for insulin (r = 0.011, NS). CONCLUSIONS: It may be stated that primary hyperaldosteronism is associated with insulin resistance at the postreceptor level. Its pathogenesis has not been elucidated so far and will be the object of future research.

Long-term treatment of mineralocorticoid excess syndromes.

Recognition of the pathogenesis of secondary forms of hypertension is often considered the key to appropriate choice of treatment. We here present the results of a prolonged clinical follow-up (from 1 to 20 years) of a large number of patients with mineralocorticoid excess syndromes (MES), including over 100 patients with primary aldosteronism (PA), 3 cases with dexamethasone-suppressible aldosteronism (DSA), 3 cases of apparent mineralocorticoid excess (AME) Type II, and 4 patients with 17-hydroxylase deficiency (17OHDS). The patients with PA have been divided in two subgroups, one of 69 cases followed between 1973 and 1982, and the second of 37 patients studied between 1983 and 1992; 33 further cases were not evaluated due to poor compliance. In group I, 26 patients underwent surgery (23 unilateral adenoma, 1 primary hyperplasia, 2 bilateral nodular hyperplasia); at 5 years 50% had normal blood pressure, 25% had mild hypertension and 25% had moderate to severe hypertension. Forty-three patients with either adenoma (APA) or idiopathic aldosteronism (IHA) received long-term spironolactone treatment. Among them, 13 required the addition of thiazide and/or beta-blockers, while 13 were switched to an amiloride/thiazide combination (+/- beta blockers) due to side-effects to spironolactone (gynecomastia 6/20 males, menstrual upset or breast pain in 7/23 females). In group II, 12 patients underwent surgery (11 adenoma, 1 primary hyperplasia) with a similar outcome at 3 years as in group I; 25 patients were put on either K canrenoate (11) or Ca++ channel blockers (14) with or without KCl supplementation; in 8 cases these two drugs were combined according to blood pressure levels achieved during the follow-up.(ABSTRACT TRUNCATED AT 250 WORDS)

Mass spectrometry in the diagnosis of steroid-related disorders and in hypertension research.

The use of GC/MS and microbore HPLC/electrospray mass spectrometry for clinical studies in hypertension and mineralocorticoid research is described. In particular, an automated GC/MS method allows nearly quantitative measurements of metabolites of major steroids of adrenal, placental and gonadal origin. This method is able to distinguish almost all steroid related disorders. Electrospray mass spectrometry in conjunction with microbore HPLC is the latest mass spectrometry technique applicable to biochemical investigations. It offers high sensitivity (15 pg) for measurement of intact steroid conjugates and related compounds.

Suppressed diluting segment reabsorption in Bartter's syndrome: studies in 1 patient and synthesis of literature data.

We analyzed renal sodium handling in a patient with Bartter's syndrome after equilibration on diets containing 200 and 700 mmol NaCl/day. No potassium supplements were given. Clearance studies were performed during maximal water diuresis, maximal free water clearance was taken as measure of diluting segment sodium reabsorption. A normal reference frame of diluting segment NaCl reabsorption at varying delivery rates to that segment was drawn from data collected in similarly studied normal subjects after equilibration on low (20 and 200 mmol/day) or very high (916-1,224 mmol/day) sodium intakes. The results were compatible with a defect in diluting segment reabsorption in the patient, which appeared more pronounced during the high sodium intake. Recent reports do not agree with the existence of such a defect in Bartter's syndrome. One of the reasons of this difference may be the lack of a proper reference frame in previously published studies. We, therefore, compared clearance data in adults with Bartter's syndrome published by others with our studies in normals. Our analysis showed that in Bartter's syndrome (1) a moderate diluting segment NaCl reabsorption defect is often present, and (2) the proximal reabsorption is frequently elevated relative to sodium intake. Severely suppressed diluting segment reabsorption and relatively low proximal reabsorption may also occur, particularly in association with salt loading or reduced glomerular filtration. It seems, therefore, that much of the continuing controversy on renal sodium handling in Bartter's syndrome may be solved by using the proper frame of reference.

Pseudohyperaldosteronism (Liddle's syndrome): a case report.

A 22-year-old man was hospitalized because of hypertension, hypokalemic alkalosis and suppressed plasma renin activity. Although these findings were similar to hyperaldosteronism, plasma aldosterone concentration and urinary aldosterone excretion were lower than the normal range. Adrenocortical function also was normal except for aldosterone. Treatment with spironolactone, salt restriction and potassium supplementation improved the hypokalemia but not the hypertension. Blood pressure decreased markedly after administration of triamterene.

Disposition of glycyrrhetic acid and its glycosides in healthy subjects and patients with pseudoaldosteronism.

As a first step to elucidate the disposition of traditional Chinese formulations which contain licorice, the disposition of plain licorice was investigated in humans. Glycyrrhetic acid (GLA) was measured by an enzyme immuno-antibody technique. Glycyrrhetic glycosides (GLA-GS), such as glycyrrhizin, were measured after acid hydrolysis to GLA by the enzyme immuno-antibody assay. Five normal subjects were orally administered a decoction of licorice containing 133 mg of glycyrrhizin. It was found that the time required for maximum serum concentration of GLA-GS was less than 4 h after the administration. Although there were large individual differences, it was found that GLA-GS was eliminated from the blood for the most part within 72 h. On the other hand, GLA reached maximum serum concentration at about 24 h after administration and in two of the five cases it was still detected in the blood even after 96 h. Urinary excretion of GLA was about 2% of the total dose of glycyrrhizin administered. This suggested that there were great differences among the subjects in the absorption and urinary excretion of GLA-GS. The serum GLA levels in two clinical cases who presented pseudoaldosteronism by licorice containing formulations were as high as 70-80 ng/ml, with GLA-GS levels being very low. This fact suggests that pseudoaldosteronism develops in association with GLA rather than with GLA-GS.

Aldosterone and other mineralocorticoids in Bartter's syndrome.

Plasma levels of aldosterone and other mineralocorticoids were determined in six patients with Bartter's syndrome. In spite of a remarkable elevation of plasma renin activity, the plasma aldosterone and 18-hydroxycorticosterone levels varied in each patient. These levels were slightly increased in three of the six patients, almost normal in two patients, and slightly reduced in one patient. The plasma deoxycorticosterone and corticosterone levels were within the normal range in all patients. The responses of plasma aldosterone to infusion of angiotensin II were reduced in all patients. Plasma aldosterone and 18-hydroxycorticosterone significantly increased with supplement of potassium, and the responses of plasma aldosterone to infusion of angiotensin II were also improved after supplement of potassium. Our results suggest that plasma aldosterone in Bartter's syndrome is dependent on potassium balance, even though plasma renin activity is remarkably increased, and that hyperaldosteronism is not an inevitable finding in Bartter's syndrome.