Role of prostaglandins in the pathogenesis of Bartter's syndrome

The Drosophila melanogaster model for Cornelia de Lange syndrome: Implications for etiology and therapeutics

Discovery of genetic alterations that cause human birth defects provide key opportunities to improve the diagnosis, treatment, and family counseling. Frequently, however, these opportunities are limited by the lack of knowledge about the normal functions of the affected genes. In many cases, there is more information about the gene's orthologs in model organisms, including Drosophila melanogaster. Despite almost a billion years of evolutionary divergence, over three-quarters of genes linked to human diseases have Drosophila homologs. With a short generation time, a twenty-fold smaller genome, and unique genetic tools, the conserved functions of genes are often more easily elucidated in Drosophila than in other organisms. Here we present how this applies to Cornelia de Lange syndrome, as a model for how Drosophila can be used to increase understanding of genetic syndromes caused by mutations with broad effects on gene transcription and exploited to develop novel therapies. © 2016 Wiley Periodicals, Inc.

Bartter's syndrome without hyperplasia of the juxtaglomerular apparatus, treated with indomethacin

The present report describes a case of potassium-wasting nephropathy with the physiological and endocrinological findings that are typical for Bartter's syndrome (BS). However, the renal juxtaglomerular apparatus showed no hyperplasia at two renal biopsies two years apart. The short-term (9 days) effect of indomethacin in combination with spironolactone was a suppression of hyperreninemia and hyperaldosteronism and an increase in vascular sensitivity to angiotensin II associated with potassium and sodium retention. Subsequently, on indomethacin alone, potassium balance was obtained on a lower level with persistent hypokalemia and persistent renal potassium leakage. Hypokalemia persisted during long-term (9 months) treatment with indomethacin despite normalization of the activity of the renin-aldosterone system. The results indicate that indomethacin as long-term treatment may be ineffective in maintaining a normal potassium balance in BS.

On the pathogenetic role of prostaglandins in Bartter's syndrome

Two patients, one with Bartter's syndrome and one with severe abuse of diuretics, were investigated before and after indomethacin treatment. Before indomethacin the two patients showed a similar pattern of hypokalaemic alcalosis, secondary hyperaldosteronism, and increased urinary excretion of PGE2 and kallikrein. After a few days on peroral indomethacin medication the hypokalaemia was significantly improved, the plasma renin activity, and the urinary excretion of aldosterone, PGE2 and kallikrein were normalized in both patients. It is concluded that the beneficial effect of indomethacin cannot be used as a proof of prostaglandin overproduction as the primary defect in Bartter's syndrome.

Salt handling in the distal nephron: lessons learned from inherited human disorders

The molecular basis of inherited salt-losing tubular disorders with secondary hypokalemia has become much clearer in the past two decades. Two distinct segments along the nephron turned out to be affected, the thick ascending limb of Henle's loop and the distal convoluted tubule, accounting for two major clinical phenotypes, hyperprostaglandin E syndrome and Bartter-Gitelman syndrome. To date, inactivating mutations have been detected in six different genes encoding for proteins involved in renal transepithelial salt transport. Careful examination of genetically defined patients (“human knockouts”) allowed us to determine the individual role of a specific protein and its contribution to the overall process of renal salt reabsorption. The recent generation of several genetically engineered mouse models that are deficient in orthologous genes further enabled us to compare the human phenotype with the animal models, revealing some unexpected interspecies differences. As the first line treatment in hyperprostaglandin E syndrome includes cyclooxygenase inhibitors, we propose some hypotheses about the mysterious role of PGE2in the etiology of renal salt-losing disorders.

Inherited primary renal tubular hypokalemic alkalosis: a review of Gitelman and Bartter syndromes

Inherited hypokalemic metabolic alkalosis, or Bartter syndrome, comprises several closely related disorders of renal tubular electrolyte transport. Recent advances in the field of molecular genetics have demonstrated that there are four genetically distinct abnormalities, which result from mutations in renal electrolyte transporters and channels. Neonatal Bartter syndrome affects neonates and is characterized by polyhydramnios, premature delivery, severe electrolyte derangements, growth retardation, and hypercalciuria leading to nephrocalcinosis. It may be caused by a mutation in the gene encoding the Na-K-2Cl cotransporter (NKCC2) or the outwardly rectifying potassium channel (ROMK), a regulator of NKCC2. Classic Bartter syndrome is due to a mutation in the gene encoding the chloride channel (CLCNKB), also a regulator of NKCC2, and typically presents in infancy or early childhood with failure to thrive. Nephrocalcinosis is typically absent despite hypercalciuria. The hypocalciuric, hypomagnesemic variant of Bartter syndrome (Gitelman syndrome), presents in early adulthood with predominantly musculoskeletal symptoms and is due to mutations in the gene encoding the Na-Cl cotransporter (NCCT). Even though our understanding of these disorders has been greatly advanced by these discoveries, the pathophysiology remains to be completely defined. Genotype-phenotype correlations among the four disorders are quite variable and continue to be studied. A comprehensive review of Bartter and Gitelman syndromes will be provided here.

Impaired response to furosemide in hyperprostaglandin E syndrome: evidence for a tubular defect in the loop of Henle

In hyperprostaglandin E syndrome (HPS) renal wasting of electrolytes and water is consistently associated with enhanced synthesis of prostaglandin E2. In contrast to Bartter or Gitelman syndrome (BS/GS), HPS is characterized by its severe prenatal manifestation, leading to fetal polyuria, development of polyhydramnios, and premature birth. This disorder mimics furosemide treatment with hypokalemic alkalosis, hypochloremia, isosthenuria, and impaired renal conservation of both calcium and magnesium. Therefore the thick ascending limb of the loop of Henle seems to be involved in HPS. To characterize the tubular defect we investigated the response to furosemide (2 mg/kg) in HPS (n = 8) and BS/GS (n = 3) 1 week after discontinuation of long-term indomethacin treatment. Sensitivity to furosemide was completely maintained in patients with BS/GS. The diuretic, saluretic, and hormonal responses were similar to those of a control group of healthy children (n = 13), indicating an intact function of the thick ascending limb of the loop of Henle in BS/GS. In contrast, patients with HPS had a marked resistance to this loop diuretic. Furosemide treatment increased urine output by 7.5 +/- 0.7 ml/kg per hour in healthy control subjects but only by 4.4 +/- 1.2 ml/kg per hour (p < 0.5) in children with HPS. In parallel, the latter also had a markedly impaired saluretic response (delta Cl(urine) 0.14 +/- 0.04 mmol/kg per hour vs 0.85 +/- 0.09 mmol/kg per hour, p < 0.001; delta Na(urine) 0.23 +/- 0.06 mmol/kg per hour vs 0.77 +/- 0.09 mmol/kg per hour, p < 0.001). Furosemide therapy further enhanced prostaglandin E2 excretion in patients with HPS (54 +/- 17 to 107 +/- 28 ng/hr per 1.73 m2, p < 0.05), whereas no significant effect was observed in healthy children (20 +/- 3 to 12 +/- 3 ng/hr per 1.73 m2). We conclude that a defect of electrolyte reabsorption in the thick ascending limb of the loop of Henle plays a major role in HPS.

Bartter's syndrome: the unsolved puzzle

Bartter's syndrome is a congenital abnormality characterized by metabolic alkalosis [corrected], hyperreninemic hyperaldosteronism, and hypokalemia. Most patients present early in life with symptoms such as muscle weakness and polyuria, which may be attributed to potassium depletion. Despite the hyperaldosteronism, the patients tend to be normotensive, which is at least partially explained by vascular hyporesponsiveness to pressor hormones. Numerous studies have documented increased renal excretion of prostaglandins. Several different patterns of aberrant renal ion transport have been observed in patients with the syndrome, suggesting that it actually may represent a family of related but distinct tubular disorders. Therapeutic approaches to Bartter's syndrome include potassium supplementation, prostaglandin synthesis inhibitors (nonsteroidal anti-inflammatory agents), aldosterone antagonists, and converting enzyme inhibitors. During the first two decades following its initial description, Bartter's syndrome was the focus of widespread interest, based on the likelihood that its investigation might provide insight into the normal functioning of the renin-angiotensin-aldosterone and prostanoid hormone systems. During the past decade, however, little additional progress has been made in Bartter's syndrome, and its patho-physiology remains poorly understood.

Diseases of renal adenosine triphosphatase

Most renal transport is a primary or secondary result of the action of one of three membrane bound ion translocating ATPase pumps. The proximal tubule mechanisms for the reabsorption of salt, volume, organic compounds, phosphate, and most bicarbonate reabsorption depend upon the generation and maintenance of a low intracellular sodium concentration by the basolateral membrane Na-K-ATPase pump. The reabsorption of fluid and salt in the loop of Henle is similarly dependent on the energy provided by Na-K-ATPase activity. Some proximal tubule bicarbonate reabsorption and all distal nephron proton excretion is a product of one of two proton translocating ATPase pumps, either an electrogenic H-ATPase or an electroneutral H-K-ATPase. In this article, the authors review the biochemistry and physiology of pump activity and consider the pathophysiology of proximal and distal renal tubular acidosis, the Fanconi syndrome, and Bartter's syndrome as disorders of ATPase pump function.

Prostanoids in paediatric kidney diseases

Prostanoids belong to the growing family of eicosanoids, which are all derived from arachidonic acid. Prostanoids act as modulators and mediators in a large spectrum of physiological and pathophysiological processes within the kidney. On the one hand, the potent vasoconstrictor and platelet-aggregating thromboxane (TX) A2 is involved in the pathophysiology of a variety of glomerular diseases, such as haemolytic-uraemic syndrome and immune-mediated glomerulopathies. Prostaglandin (PG) E2, on the other hand, interferes with tubular electrolyte and water handling. Clinical data support the hypothesis that this member of the prostanoid family contributes to the pathophysiology of Bartter's syndrome, hyperprostaglandin E syndrome, idiopathic hypercalciuria and renal diabetes insipidus. Both prostanoids, TXA2 and PGE2, are involved in the pathophysiology of obstructive uropathies. The physiological and protective role of renal vasodilator prostanoids (PGI2 and PGE2) has been studied during treatment with non-steroidal anti-inflammatory drugs. Part of the pharmacological effects of frusemide and converting enzyme inhibitors is mediated by PGI2 and PGE2. The role of renal prostanoids in cyclosporine toxicity is still equivocal. Future investigations on the physiological and pathophysiological role of renal prostanoids will have to consider the multiple interactions between prostanoids on the one hand, and classical hormones and other mediators (e.g. cytokines) on the other hand.

Evidence that circulating 6keto prostaglandin E1 causes the platelet defect of Bartter's syndrome

Bartter's syndrome is associated with activation of prostaglandin metabolism. In the present study we provide several lines of evidence that a circulating metabolite of prostacyclin, 6ketoPGE1 is responsible for a defect in platelet function present in patients with Bartter's syndrome. In platelet aggregometry studies, plasma from patients contained platelet inhibitory activity which was fully neutralized by coincubation with antibody directed against 6ketoPGE1. Fractionation of lipophilic extracts of plasma by high pressure liquid chromatography yielded a platelet inhibitory fraction which comigrated with authentic 6ketoPGE1 and was neutralized by anti 6ketoPGE1 antibody. Lastly, direct measure of the plasma concentration of 6ketoPGE1 by specific radioimmunoassay indicates a 2-fold increase in patients with Bartter's syndrome (133 +/- 9.1 vs 60.7 +/- 12.3 picograms/ml; p less than 025). These studies provide firm evidence that the platelet dysfunction present in patients with Bartter's syndrome is attributable to an increase in the plasma concentration of 6ketoPGE1. In addition, these data provide further evidence in support of the centrality of activation of prostaglandin metabolism in the pathophysiology of Bartter's syndrome.

Bartter's syndrome and diabetes mellitus

We here report a case of Bartter's syndrome occurring in association with diabetes mellitus. The patient, an insulin-dependent diabetic, presented with hypokalaemia, inappropriate kaliuresis and metabolic alkalosis. He had high plasma renin activity, relatively low plasma aldosterone, and resistance to infused angiotensin II. A high potassium diet raised total body potassium and serum potassium, did not affect plasma renin activity, but raised plasma aldosterone significantly and did not alter the resistance to angiotensin II. Indomethacin administered acutely reduced urinary potassium and kallikrein excretion and, on chronic administration, lowered plasma renin activity, urinary chloride excretion, and raised serum potassium. Salt restriction resulted in a prompt and significant reduction in urinary sodium and chloride excretion. Urinary kallikrein excretion was very high throughout, increased with sodium restriction, and decreased with sodium loading. Oral potassium supplementation partially corrected the hypokalaemia, but did not affect blood sugar control. In this patient the primary defect appears to have been primary urinary potassium wasting, rather than sodium or chloride wasting. The striking effects of indomethacin suggest that prostaglandins may play a fundamental role in the genesis of the syndrome.

Exogenous prostaglandin administration and pseudo-Bartter syndrome

Biological abnormalities simulating Bartter syndrome were observed in a preterm neonate with complex cyanotic congenital heart disease, for which ductus arteriosus was maintained open by high doses of prostaglandin (PG) until a Blalock shunt could be performed. These abnormalities spontaneously disappeared after cessation of PG administration. We postulate that the natriuretic effect of exogenous administered PG could further increase sodium wasting already induced by the cardiopathy thus leading to pseudo-Bartter syndrome.

Bartter's syndrome. A review of 28 patients followed for 10 years

Twenty-eight patients with Bartter's syndrome diagnosed during the years 1964-86 and followed for an average of 9.9 years have been reviewed. Their mean age at the time of diagnosis was 32.9 years. As a group they were shorter than normal subjects. In 19 patients hypokalaemia was detected incidentally. Neuromuscular symptoms, usually minor, had occurred in 19 subjects. Pregnancies and deliveries were unremarkable. One patient has died from malignant lymphoma, the others are alive. Of these, one patient has developed renal failure and received a renal transplant. The other patients have preserved a normal renal function and the majority have been healthy and working full time. Treatment rarely resulted in normokalaemia. The annual incidence of the syndrome has been estimated at 1.2 per million people.

Growth from birth to adulthood in a patient with the neonatal form of Bartter syndrome

Growth from birth to the age of 19 years was studied in a patient with the neonatal form of Bartter syndrome. The initial modes of therapy (extra fluid, potassium supplements and triamterene) resulted in satisfactory but not optimal growth. Treatment with spironolactone together with potassium led to impressive catch-up growth. When the patient reached the age of 9 years, indomethacin therapy was started, which resulted in a second growth acceleration and was also accompanied by a significant reduction of both polyuria and hypercalciuria. Puberty developed normally, menarche occurred at 12 years 4 months and a normal adult height of 162 cm was reached at the age of 14 years. Treatment with prostaglandin synthetase inhibitors seems to be the best therapy for children with the neonatal form of Bartter syndrome.

[Secondary gout and pseudo-Bartter syndrome in females with laxative abuse]

Four females (27-54 y), presenting with a history of long-term laxative abuse, were admitted to the Medizinische Poliklinik for evaluation of generalized weakness. Laboratory findings revealed signs of Bartter's syndrome, including hypokalemia, systemic alkalosis and normal blood pressure. Three of the four females showed impaired renal function and elevated serum uric acid levels, two of them suffered from recurrent gouty attacks. In our patients the incidence of hyperuricemia and impaired renal function, as a consequence of chronic hypokalemia, was much higher than known from patients with Bartter's syndrome. Hyperuricemia is related to some pathophysiological features of Pseudo-Bartter's syndrome, (e.g. systemic alkalosis, elevated angiotensin) and combined with additional factors (e.g. catabolism, reduced plasma volume) may lead to gouty attacks. Gallstones were found in two of the four females. Long term surreptitious laxative ingestion frequently is observed in females. Hypokalemia, induced by the laxatives, causes reduced intestinal motility and leads to augmented laxative intake. These patients are prone to develop Pseudo-Bartter's syndrome, causing eventually a hyperuricemia and gouty attacks.

Role of prostaglandins in hyperprostaglandin E syndrome and in selected renal tubular disorders

Renal and systemic prostanoid activity was assessed in various renal tubular disorders, using mass spectrometric determination of urinary excretion rates of primary prostaglandins (PGE2, PGF2 alpha, PGI2, and TXA2) and their systemically produced index metabolites. Only PGE2 levels (normal range: 2.0-16.4 ng/h per 1.73 m2) are elevated in Bartter syndrome (median: 43.4, range: 6.7-166.3), nephrogenic diabetes insipidus (46.2, 12.1-1290), Fanconi syndrome (96.6, 19.3-135.5), and in a complex tubular disorder in premature infants (40.7, 22.3-132.1), for which the term hyperprostaglandin E syndrome has been introduced. In this disorder with a Bartter-syndrome-like tubulopathy, the systemic features of the disease such as fever, diarrhoea and osteopenia with hypercalciuria were associated with increased systemic PGE2 activity. In most patients the urinary excretion rate of the systemic index metabolite of PGE2 (PGE-M) was markedly elevated (1028, 285-4709; normal range: 104-664 ng/h per 1.73 m2). Hypercalciuria per se was associated neither with increased renal nor with systemic PGE2 hyperactivity. Most problems in infants with hyperprostaglandin E syndrome could be controlled by long-term indomethacin treatment in contrast to the moderate and partial effect of this treatment in patients with Fanconi syndrome. Thus increased PGE2 synthesis plays a major role in the pathogenesis of hyperprostaglandin E syndrome, while in Fanconi syndrome PGE2 hyperactivity in the kidney is a secondary event and only aggravates the water and electrolyte wastage.

A Bartter's-like syndrome from capreomycin, and a similar gentamicin tubulopathy

Marked renal potassium and magnesium wasting, alkalosis, and a progressive increase in plasma renin and eventual hyperaldosteronemia developed during a 15-month course of in-hospital capreomycin therapy that was necessary for drug-resistant pulmonary tuberculosis. A prominent feature of the present case was renal chloride wasting, a feature of the capreomycin syndrome that has previously received little attention. Similar potentially life-threatening metabolic abnormalities, which resemble those found in Bartter's syndrome, can occur during prolonged therapy with the antibiotic gentamicin. In the present case, electrolyte abnormalities were unaffected by three days of indomethacin therapy but were partially corrected by large doses of spironolactone. Capreomycin, viomycin (an antibiotic closely related to capreomycin), and gentamicin are highly basic polypeptide antibiotics that may induce strikingly similar and potentially fatal syndromes of renal tubular dysfunction that can feature multiple electrolyte abnormalities.

Effect of prostaglandins on renal salt and water excretion

There are several important mechanisms by which renal prostaglandins modulate renal salt and water excretion. The role of endogenous renal prostaglandins in facilitating urinary sodium excretion and the individual nephron segments that are affected by renal prostaglandins are reviewed. The role of the administration of nonsteroidal anti-inflammatory agents on the kidney's ability to excrete salt and water both physiologically and clinically is summarized. The potential role for endogenous prostaglandins to antagonize the effect of antidiuretic hormone and to alter renal water excretion is also described. The clinical consequences of taking nonsteroidal anti-inflammatory drugs in terms of hyperkalemia, sodium retention with associated edema, and possible hyponatremia are all discussed. Although these clinical consequences are quite uncommon statistically, there are certain subsets of patients for whom additional concern is important.

Congenital hypokalemia with hypercalciuria in preterm infants: a hyperprostaglandinuric tubular syndrome different from Bartter syndrome

A congenital hypokalemic tubular disorder is described with many features resembling Bartter syndrome. Additional features include prenatal onset with polyhydramnios and premature labor; failure to thrive; episodes of fever, vomiting, diarrhea, and renal electrolyte and water wastage; hypercalciuria; nephrocalcinosis; and osteopenia. Unlike Bartter syndrome, there is no defect in tubular reabsorption of chloride. Urinary levels of prostaglandin E2 and 7 alpha-hydroxy-5,11-diketotetranorprosta-1,16-dioic acid are selectively elevated, indicating marked stimulation of renal and systemic PGE2 production. Chronic suppression of PGE2 activity by indomethacin corrects most of the abnormalities, and there is an immediate decompensation of the disease on indomethacin withdrawal. We conclude that these preterm infants have a distinct variety of hypokalemic tubular disorders rather than a variant of Bartter syndrome, because renal and systemic hyperprostaglandinism ranks high in the pathogenic chain of events, and the suppression of PGE2 hyperactivity is associated with significant improvement in the development (and probably in the prognosis) of the affected children.

Inhibition of the kallikrein-kinin system and vascular reactivity in Bartter's syndrome

To study the significance of the increased activity of the kallikrein-kinin system described in patients with Bartter's syndrome, we investigated the pressor response to infused angiotensin II in four patients with the syndrome receiving no treatment and during the administration of aprotinin and of indomethacin. Five normal subjects served as controls. Aprotinin is a proteolytic enzyme that inhibits the formation of kinins by inhibiting plasma and glandular kallikrein. Indomethacin, a prostaglandin-synthesis inhibitor, can also inhibit the kallikrein-kinin system and normalizes vascular responsiveness to angiotensin II in Bartter's syndrome. All patients had increased urinary kallikrein and prostaglandin E2 concentrations. Aprotinin significantly decreased the dose of infused angiotensin II required to induce a 20 mm Hg increase in diastolic blood pressure, from 11 +/- 4 ng/kg/min to 7.0 +/- 2.0 ng/kg/min (mean +/- SD; p less than 0.05) in normal subjects and from 135 +/- 57 ng/kg/min to 70 +/- 26 ng/kg/min (p less than 0.05) in the patients with Bartter's syndrome, without significantly changing plasma renin activity, mean control blood pressure, or urinary prostaglandin E2 concentration. Indomethacin normalized the pressor response to angiotensin II in three patients who had been pretreated for 4 days (pressor dose, 10 ng/kg/min) but not in one patient who received a single oral dose of indomethacin 5 hours before the test. Our results suggest that inhibition of the kallikrein-kinin system alone accounts for approximately a 50% decrease in vascular resistance to the pressor effect of angiotensin II in Bartter's syndrome, while additional suppression of prostaglandins entirely normalizes the vascular response to angiotensin II.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood to interstitial fluid volume ratio in chronic hypokalaemic states

The distribution of extracellular fluid over the intra- and extravascular spaces was determined in hypokalaemic and normokalaemic patients. In six patients with Bartter's syndrome, four with pseudo-Bartter's syndrome, and twenty with essential hypertension (EH) chronically treated with chlorthalidone, serum potassium (serum K+) and extracellular fluid volume (ECFV) were decreased, while plasma volume (PV) and blood volume (BV) were normal (see Table 1 for means, standard deviations, and levels of significance). Consequently, the ratio of BV to interstitial fluid volume (IFV) was increased. In ten patients with EH on long-term combined enalapril chlorthalidone therapy, eight EH patients on long-term spironolactone treatment, and twenty-three EH patients treated by short-term sodium restriction, PV, BV, and ECFV were decreased, but serum K+ and BV/IFV were normal. In six patients with primary hyperaldosteronism (PHA) serum K+ was decreased, while PV, BV, and BV/IFV were elevated. Significant negative correlations between sK and BV/IFV were found in the Bartter patients (r = -0.88) and the pooled data of all patients (r = -0.50). These findings suggest an association between chronic hypokalaemia and a fluid shift from the extra- into the intravascular space. The hypothesis that this phenomenon is due to a decreased venous resistance as a consequence of chronic hypokalaemia is discussed.

Reversal of Bartter's syndrome by renal transplantation in a child with focal, segmental glomerular sclerosis

A four-year-old girl with growth failure and clinical and laboratory evidence of Bartter's syndrome responded to indomethacin treatment with decreased urinary prostaglandin excretion, symptomatic and chemical improvement, and accelerated growth. Large doses of aspirin produced a comparable decrease in prostaglandin excretion but no improvement in any other metabolic abnormality thus suggesting that abnormalities in prostaglandins were the result rather than the cause of the electrolyte abnormalities. Progressive renal insufficiency while on indomethacin prompted a renal biopsy, which revealed morphological changes of focal, segmental glomerular sclerosis. Subsequently, the child underwent renal transplantation with complete resolution of symptoms and abnormal metabolic findings. This observation suggests that extrarenal factors were not responsible for the development of Bartter's syndrome in this child.

Urinary prostaglandins in Bartter's and pseudo-Bartter's syndrome

Renal secretion of prostaglandins (PG) in Bartter's syndrome and in different forms of hypokalemic normotensive syndromes (pseudo-Bartter's syndrome) was measured to determine if it is possible to use the measurement of urinary prostaglandins for the discrimination of different etiologies. Prostaglandins E2, F2 alpha, 6-keto-PGF1 alpha and thromboxane B2 (TxB2) were measured after extraction and chromatography by radioimmunoassay in 19 patients and in 26 control healthy subjects. Bartter's syndrome may be characterized as primary renal hyperprostaglandinism with high urinary PGE2 excretion. It can be dissociated from pseudo-Bartter's syndrome because the urinary PGE2 excretion is always in the normal range in the pseudosyndrome. Abuse of loop diuretics may have effects that mimic Bartter's syndrome since these diuretics stimulate urinary prostaglandin excretion. Therefore, loop diuretics should always be excluded prior to the diagnosis of Bartter's syndrome.

Clinical syndromes associated with disorders of renal tubular chloride transport: excess and deficiency of a circulating factor?

Two contrasting patients are described, one with pseudo-Bartter's syndrome induced by frusemide abuse and the other a case of hyporeninaemic hypoaldosteronism. The clinical and biochemical features of these two conditions are the opposite of each other and, in the first patient, the effects of frusemide were antagonised by treatment with indomethacin while in the second frusemide itself corrected the syndrome. The decreased pressor sensitivity to infused angiotensin II seen in the patient with pseudo-Bartter's syndrome was corrected with indomethacin and the enhanced pressor sensitivity seen in hyporeninaemic hypoaldosteronism was reversed with frusemide. Frusemide, an agent which blocks chloride transport at the ascending limb of Henle's loop, was respectively thus the cause and the cure of these conditions. On the basis of this the suggestion is made that Bartter's syndrome and hyporeninaemic hypoaldosteronism represent respectively an excess and a deficiency of a circulating factor similar to frusemide capable of blocking renal tubular chloride transport.

The value of urinary chloride measurement in distinguishing surreptitious vomiting from Bartter's syndrome

Urinary chloride measurement is a simple and common procedure but its value in clinical practice is not extensive. This case report highlights a practical and important use of this test. A patient presented with most of the clinical and metabolic derangements of Bartter's syndrome but was found to have extremely low or absent urinary chloride excretion. Her ability to excrete chloride was, however, intact during a chloride load test. The finding of low urinary chloride excretion did not support the diagnosis of Bartter's syndrome and suggested an extrarenal loss of chloride. This was confirmed when she eventually admitted to surreptitious vomiting.

Comparison of prostaglandin production of skin fibroblasts grown from patients with Bartter's syndrome and from age and sex matched controls

Basal and bradykinin stimulated release of prostaglandins (6-oxo-PGF1 alpha, PGF2 alpha, PGE2) and of arachidonic acid (C20:4) from skin fibroblast cultures of two patients with Bartter's Syndrome were compared with age and sex matched controls. PG-formation from 14C-C20:4 was studied, and for PGE2 a radioimmunoassay was also employed. The data show that in basal release, Bartter's Syndrome fibroblasts produce significantly less PGE2 than controls. Stimulated release of 6-oxo-PGF1 alpha was higher, that of PGE2 lower and that of C2O:4 higher in Bartter's Syndrome than in controls, all differences being significant. Despite equal culturing conditions the estimated intracellular potassium was higher in the patients fibroblasts than in controls. In skin fibroblasts from patients with Bartter's Syndrome stimulated prostaglandin production from C2O:4 is mostly depressed, with the exeption of prostacyclin which is enhanced. The permeability of cell membranes for potassium might play a pathogenetic role.

Independent roles of prostaglandins and the renin-angiotensin system in abnormal vascular reactivity in Bartter's syndrome

To clarify the independent roles of prostaglandins and the renin-angiotensin system in the pressor resistance to angiotensin II in Bartter's syndrome, the pressor responsiveness to exogenous angiotensin II was investigated in three patients with the syndrome during the administration of indomethacin synthesis, and captopril is an angiotensin-converting enzyme inhibitor. All the patients showed high plasma renin activity, increased urinary excretion of prostaglandin E, and pressor resistance of angiotensin II. An analogue of angiotensin II that had weak agonistic properties induced a marked fall in blood pressure. Pretreatment with indomethacin (150 mg/day) decreased baseline plasma renin activity and reversed the hypotensive effect of the analogue of angiotensin II. Apparently, our data support the concept that pressor resistance ultimately results from the increase in the concentration of endogenous angiotensin II. However, the augmentation of indomethacin was significantly (p less than 0.01) greater in magnitude than the response obtained with captopril, although the concentration of plasma angiotensin II prior to each infusion of angiotensin II was the same. This observation could be explained by the finding that indomethacin suppressed both systems, but captopril inhibited only the renin-angiotensin system. Evidence presented herein suggests that the abnormalities in the vascular reactivity to angiotensin II may result from, not only the decreased number of receptor sites as a results of the increased concentration of endogenous angiotensin II, but also from the alteration of the end-organ sensitivity to angiotensin II via overproduction of prostaglandins.

Surreptitious diuretic ingestion and pseudo-Bartter's syndrome

A patient with profound hypokalemia satisfied the criteria for Bartter's syndrome, including hyperreninemia, aldosteronism, normal blood pressure, and hyperplasia of the juxtaglomerular apparatus. Two screening tests of urine and one of plasma for diuretic agents gave negative results. A third urinary sample gave negative results for thiazide but positive for furosemide; the fourth and fifth samples gave negative results for furosemide but positive for thiazide. Urinary prostaglandin excretion was normal. We conclude that this apparent case of Bartter's syndrome was caused by long term surreptitious diuretic ingestion and suggest this may occur more frequently than is generally appreciated.

Familial Bartter's syndrome and the effect of indomethacin in one family member

A Japanese family in which a father, daughter and son had hypokalemia and hyperreninemia was investigated. Both father and daughter had reduced vascular sensitivity to angiotensin II; in addition, the daughter had juxtaglomerular cell hyperplasia and dwarf glomeruli. These features are consistent with Bartter's syndrome occurring in 2 successive generations in 1 family. The 12-year-old girl had growth retardation in spite of normal growth hormone secretion. No chromosomal abnormalities were found. Indomethacin administration to this patient in doses sufficient to reduce urinary prostaglandin excretion resulted in a marked improvement of polydipsia and polyuria, and an increase in serum sodium, potassium and chloride concentrations. Even though plasma aldosterone concentrations were reduced to within the normal range, serum potassium concentrations remained low, and plasma renin activity (PRA) remained elevated. Thus it is not likely that hypokalemia is induced only by aldosteronism. These results suggest that prostaglandins are the major determinant of polydipsia, polyuria and high plasma aldosterone levels and contribute to the hypokalemia observed in this patient. However, the failure of complete correction of the hypokalemia and the persistence of the raised PRA with a significant reduction of the prostaglandins suggest the possibility that additional factors are involved in the pathogenesis of Bartter's syndrome.

Arachidonic acid metabolism, prostaglandins and the kidney

Renal prostaglandins are gaining increasing recognition as important modulators of hemodynamics and excretory function in the mammalian kidney. Synthesis of these unsaturated fatty acids from arachidonate precursors is closely regulated by intrarenal factors, and circulating angiotensin II, catecholamines, arginine vasopressin and bradykinin. Endogenous prostaglandins exert little influence on renal blood flow and glomerular filtration rate in the basal state, but inhibition of arachidonate metabolism when renal perfusion is impaired causes marked alterations in these parameters. Renal salt and water excretion is modified by the effects of prostaglandins on glomerular filtration rate, proximal tubule fluid reabsorption, medullary solute gradients, and the intrinsic water and ion reabsorptive properties of distal nephron segments. Prostaglandins also mediate renin release under basal conditions and in response to intravascular volume depletion. Abnormalities of renal prostaglandins are evident in various clinical disorders of renal function including hypertension, ureteral obstruction, Bartter syndrome, hypokalemic nephropathy and drug-induced disorders of water metabolism. Appropriate clinical use of nonsteroidal anti-inflammatory agents requires consideration of the potential renal consequences of inhibiting prostaglandin biosynthesis.

The effect of vasopressin in water-loaded hypokalemic patients is prostaglandin-independent

Potassium-depleted subjects regularly excrete dilute urine with a high free-water clearance which cannot be suppressed either by solute loading or by water deprivation. In man, as in the dog and rat, potassium depletion impairs the ability of the kidney to achieve maximal urinary solute concentration and vasopressin is unsuccessful in overcoming this defect. In man and in the dog, potassium depletion induces a rise in urinary prostaglandin E2, an effect which can be reversed with indomethacin, a cyclo-oxygenase inhibitor. To evaluate the role of prostaglandins on the renal action of vasopressin in hypokalemia, six subjects with hypokalemia of various etiologies were studied in a control, drug-free condition and again after 3 to 6 days of indomethacin (100 mg/day). Renal clearance studies to measure the maximal free-water excretion in response to an intravenous water load (10 ml/min) and to a superimposed infusion of arginine vasopressin (40 mU/hr) were performed. The results in six patients are as follows: maximal free-water clearance (control) 8.03 +/- 0.8 ml/min (mean +/- S.E.), with the addition of vasopressin, .14 +/- 0.8; after 3 to 6 days of indomethacin, 8.55 +/- 1.33; with vasopressin 0.91 +/- 1.23 ml/min. There was no statistically significant difference between the maximal free water clearance with or without indomethacin. Vasopressin exerted an equally great response in both conditions and prostaglandins did not appear to play a role in free-water formation.

Factors influencing vascular hyporesponsiveness to angiotensin II

Bartter's syndrome is characterized, in part, by hyporesponsiveness to the pressor effect of exogenous angiotensin II (AII). This has been attributed to volume contraction, hypokalemia, and/or increased prostaglandin (PG) levels. In order to investigate factors responsible for a diminished response to the pressor effect of AII, rats were made hypokalemic or volume contracted and hypokalemic (VCHK) by dietary restriction. AII sensitivity was examined by determining the dose of AII required to raise the mean arterial pressure 20 mm Hg. When compared with control rats. VCHK and hypokalemic rats were significantly less sensitive to AII. VCHK rats were significantly less sensitive to AII than hypokalemic rats. Both experimental groups were similarly hypokalemic, but plasma renin activity (PRA) of VCHK only was greater than control values. In VCHK rats, acute K+ restoration partially corrected AII hyporesponsiveness, although plasma K+ increased to normal. In VCHK rats, acute volume expansion with normal saline similarly achieved only partial correction of AII hyporesponsiveness although PRA values fell to the control range. Simultaneous K+ restoration and volume expansion to VCHK rats successfully restored AII sensitivity to the control range. Dietary sodium, chloride, and potassium restriction did not increase urinary excretion to PGE2. Indomethacin (5 mg/kg, iv) given acutely to VCHK rats did not significantly after baseline hyporesponsiveness to AII. Norepinephrine vascular sensitivity was not affected by either volume contraction or hypokalemia. These data demonstrate that volume contraction and hypokalemia individually depress exogenous AII sensitivity in the rat and do so by separate and additive mechanisms. Furthermore, these mechanisms appear to be independent of PG.

Prostaglandins and steroidogenesis in isolated bovine adrenal cells. Effects of ACTH, prostaglandin-synthesis inhibitors, prostaglandins and prostaglandin analogs

In bovine adrenal cortex cells, dispersed without preferential loss of cells, we investigated (1) whether endogenous prostaglandins (PGs) are involved in ACTH-induced adrenal steroidogenesis, and (2) the steroidogenic effects of PGs and PG analogs. Free cells produced considerable amounts of PGE2, whereas only minute quantities of PGF2 alpha and PGA1 were synthesized. PGE2 synthesis, however, was not significantly increased when ACTH elicited a steroidogenic response in free cells. High concentrations of PG-synthesis inhibitors such as indomethacin affected both PG synthesis and steroidogenesis, whereas intermediate concentrations (10(-6) M) inhibited production of both PGE2 and aldosterone even after cAMP and cortisol response to ACTH had returned to normal values. It is concluded that endogenous PGE2 is not a link in the acute mechanism of action of trophic hormones in which cAMP is involved. Of the prostanoid structures, PGs of the E series were the most potent stimulating agents of cortisol production, although less active than ACTH. On the other hand, PGA1 induced an ACTH-like aldosterone synthesis. PGE2 was less active, and other prostanoid structures were without effect on aldosterone production. It is suggested that in pathological circumstances, PGA1 regulates aldosterone production and PGE2 increases both aldosterone and cortisol production.

Effect of indomethacin on urinary kallikrein excretion in Bartter's syndrome of the adult

An elevated urinary kallikrein excretion was found in 3 out of 4 adult patients with Bartter's syndrome. After prostaglandin synthesis inhibition by indomethacin, serum potassium levels rose, plasma renin activity and urinary aldosterone excretion decreased. Urinary kallikrein excretion was reduced to within normal range in all patients. The fall of urinary kallikrein excretion after indomethacin may be partly due to plasma potassium and aldosterone variations, but more likely it is dependent on the reduced prostaglandin synthesis. These results support the hypothesis that renal prostaglandins activate renal kallikrein-kinin system, hence inducing an increase of renal blood flow, diuresis and natriuresis.