Responsiveness of Hypercalciuria to Thiazide in Dent’s Disease
Khalid A Raja*,
Scott Schurman,
Richard G. D’Mello*,
Douglas Blowey,
Paul Goodyer¶,
Scott Van Why,
Robert J. Ploutz-Snyder*,
John Asplin# and
Steven J. Scheinman*
Departments of *Medicine and Pediatrics, SUNY Upstate Medical University, Syracuse, New York; Section of Pediatric Nephrology, The Children’s Mercy Hospital, Kansas City, Missouri; ¶Department of Pedatrics, McGill University, Montreal, Canada; Department of Pediatrics, Yale University School of Medicine, New Haven, Connecticut; and #Department of Medicine, University of Chicago Pritzker School of Medicine, Chicago, Illinois.
Correspondence to Dr. Steven J. Scheinman, Professor of Medicine, SUNY Upstate Medical University, 750 E. Adams Street, Syracuse, NY 13210. Phone 315-464-5290; Fax: 315-464-5295;E-mail: scheinms{at}upstate.edu
ABSTRACT. Hypercalciuria is the major risk factor promotingstone formation in Dent’s disease, also known as X-linkedrecessive nephrolithiasis, but the effects of diuretics on calciumexcretion and other stone risk factors in this disease are unknown.This study examined urine composition in eight male patientswith Dent’s disease, ages 6 to 49 yr, all of whom werehypercalciuric and had inactivating mutations of CLCN5. Eightmales, ages 7 to 34 yr, with idiopathic hypercalciuria (IH)served as controls. Patients were instructed to maintain a consistentintake of sodium, potassium, calcium, and protein. Two consecutive24-h urine collections were obtained after a baseline periodand after 2 wk of chlorthalidone (25 mg), amiloride (5 mg),and the two diuretics in combination, with a week off drug separatingthe treatment periods in a randomized crossover design. Doseswere reduced by half in boys under age 12 yr. Chlorthalidonealone (P < 0.002) and the combination of chlorthalidone andamiloride (P < 0.003) reduced calcium excretion significantlyin either patient group. With chlorthalidone, calcium excretionfell to normal (<4.0 mg/kg per d) in all but one patientin each group. Amiloride alone had no significant effect onurinary calcium excretion, in either patient group. In patientswith Dent’s disease during chlorthalidone therapy, thesupersaturation ratios for calcium oxalate and calcium phosphatefell by 25% and 35%, respectively. Mean citrate excretion wasreduced by chlorthalidone (P < .04) and by chlorthalidonein combination with amiloride (P < .02). There were no significantdifferences in the responses to these diuretics between thepatient groups in any of the urinary parameters. The intacthypocalciuric response to a thiazide diuretic indicates thatinactivation of the ClC-5 chloride channel does not impair calciumtransport in the distal convoluted tubule and indicates thatthiazides should be useful in reducing the risk of kidney stonerecurrence in patients with Dent’s disease.
Dent’s disease, also known as X-linked recessive nephrolithiasis,is an hereditary condition characterized by hypercalciuria,nephrocalcinosis, kidney stones, proteinuria, progressive renalfailure, and, in some patients, rickets. It is associated withmutations that inactivate the voltage-gated chloride channelClC-5 (1–5). This channel is expressed in intracellularmembranes of the cortical proximal tubule, medullary thick ascendinglimb, and -intercalated cells of the human nephron (6).
Nephrocalcinosis occurs in 75% and kidney stones in 50% of affectedmales with Dent’s disease (5,7). The major risk factorpromoting stone formation in this disease is hypercalciuria,which is present in most affected males until the onset of renalinsufficiency. Calcium excretion can exceed 10 to 12 mg/kg perday in young boys, but the range of calcium excretion in teenageand adult males with Dent’s disease (4 to 6 mg/kg perday) is similar to that seen in patients with idiopathic hypercalciuria(IH). Urinary excretion of oxalate, citrate, and uric acid isusually normal. Oral calcium loading in hypercalciuric patientswith Dent’s disease reveals an exaggerated postabsorptiverise in urinary calcium excretion; some of these (particularlychildren) have fasting hypercalciuria as well. This occurs inthe setting of suppressed serum levels of parathyroid hormoneand often elevated levels of 1,25-dihydroxyvitamin D (5,8).This pattern of calcium handling is also found in many patientswith IH.
Therapies to reduce stone risk in Dent’s disease havenot been evaluated formally. Thiazide diuretics have been shownto be effective in correcting hypercalciuria and reducing therate of stone recurrence in patients with IH (9–11). However,thiazides promote hypokalemia, which can lower urinary citrateexcretion. Citrate reduces stone risk by lowering ionized calciumin the urine and inhibiting crystallization of calcium oxalate(12). Hypokalemia occurs spontaneously in about one third ofpatients with Dent’s disease (5,7). Amiloride also increasesdistal tubular calcium reabsorption and has been used as a therapyfor idiopathic hypercalciuria. Although amiloride alone appearsto be less effective than thiazide in reducing calcium excretion,amiloride may potentiate the beneficial effect of thiazideson hypercalciuria and reduce the risk of hypokalemia and alkalosis(13,14).
We studied the effects of thiazide, amiloride, and the combination,on the urinary stone risk profile in patients with Dent’sdisease and in a similar group of patients with IH.
Subjects
We studied eight male patients with Dent’s disease andeight male patients with IH. Baseline data on these individualsare given in Table 1. The diagnosis of Dent’s diseasewas based on the presence of low–molecular weight proteinuria,hypercalciuria, and microscopic hematuria in a patient witha documented mutation in the CLCN5 gene. We excluded patientswhose GFR (measured by clearance of creatinine or iothalamate)was below 80% of the mean of normal for age. Patients with IHwere found to be hypercalciuric on evaluation for kidney stones.All subjects were documented to have hypercalciuria (>300mg/d or >4 mg/kg per d) on multiple 24-h urine collectionswhile ingesting a random diet. All patients had normal serumcalcium levels. Subjects were excluded if they had any othercondition that could cause hypercalciuria such as hyperparathyroidism,inflammatory disease, cancer, thyrotoxicosis, Paget disease,Addison disease, or other such conditions. Patients were excludedif they had any contraindication to therapy with either chlorthalidoneor amiloride, such as a prior untoward reaction or allergy tothese drugs. Any diuretics were discontinued, and no subjectwas taking any medications other than as specified in the protocolduring the 10 wk of the study. The study was approved by theInstitutional Review Board for the Protection of Human Subjectsof the Upstate Medical University, as well as those of the otherparticipating institutions, and informed consent was obtained.
Table 1. Patient characteristics on entry into studya
Study Protocol
Patients were instructed to follow a diet containing a moderateamount of sodium (2 to 4 g) and calcium (800 mg) similar tothat used in our previous study of calcium excretion in X-linkednephrolithiasis (8). After a baseline evaluation consistingof a review of available data regarding eligibility (see InclusionCriteria), a medical examination, and measurement of serum electrolytesand calcium levels, patients were observed through a baselineperiod of 2 wk on no treatment followed by three treatment phasesof 2 wk each in which they received 25 mg of chlorthalidonedaily, 5 mg of amiloride daily, and the combination of 25 mgof chlorthalidone plus 5 mg of amiloride daily. Diuretic doseswere reduced by 50% in boys 11 yr old. Patients were randomizedat entry to receive one of six potential protocols with differentsequences for these three treatment periods. At the end of thebaseline period and each treatment period, two successive 24-hurine collections were obtained. Treatment periods were separatedby a 1-wk washout period off diuretics (Figure 1).
Figure 1. Summary of study protocol. DQ, dietary questionnaire.
Twenty-four–hour urine specimens were analyzed for a completestone panel, which includes measurement of calcium, phosphorus,oxalate, citrate, sodium, potassium, magnesium, uric acid, pH,ammonium, creatinine, and other measures, as well as calculationof supersaturation ratios for calcium oxalate, calcium phosphate,and uric acid. These measurements were made at the Kidney StoneResearch Laboratory at the University of Chicago (15). Valuesfor a given 24-h collection were excluded from analysis if thecreatinine excretion on that collection varied by more than15% or the sodium excretion varied by more than 25% from themean of values for other collections by that patient; thesecriteria were specified in advance of the study. Of the 128duplicate 24-h urine collections obtained from the 16 patientsincluded in four phases of this study, 14 were discounted becausethey failed to meet these criteria. In each case, a duplicatespecimen was available.
One patient with Dent’s disease discontinued the studybecause of inability to tolerate diuretic therapy, and anotherpatient with Dent’s disease was excluded from the studybecause urinary creatinine and sodium values revealed that hehad failed to follow instructions throughout the study. Thedata shown represent the remaining eight patients with Dent’sdisease.
Compliance with dietary instructions was also monitored throughdietary questionnaires administered at the end of each studyperiod. Dietary content of sodium, calcium, calories, and proteinwere estimated from the responses to these questionnaires, andintake was analyzed by ANOVA as described below. There wereno significant differences in these measures between patientgroups or across treatment periods.
Statistical Analyses
Patients served as their own control for this study, using theinitial period of observation on the study diet alone as a baseline.Treatment, therefore, represents a repeated-measures factorin our experimental design. Each data point for analysis representsthe subjects’ mean of measurements made on duplicate 24-hurine collections, except when one of the duplicates was excludedby virtue of the criteria described above.
The data were submitted to a two-factor, mixed-model ANOVA,setting = 0.05. Our design crossed four within-subjects treatments(baseline, chlorthalidone, amiloride, and chlorthalidone plusamiloride) with two between-subjects conditions (Dent’sdisease and IH). This design enabled us to examine overall treatmenteffects regardless of condition, overall condition effects regardlessof treatment, and the potential for an interaction of conditionand treatment whereby patterns of responses to the three treatments(relative to control) were different in patients with IH andDent’s disease. Because we were specifically interestedin evaluating chlorthalidone, amiloride, and the combinationof both diuretics in comparison with baseline measures, we alsoincluded a priori contrasts in the analysis comparing each levelsof treatment to baseline control.
Baseline Measurements
Data obtained from the baseline period, on the study diet andwithout diuretics, are summarized in Table 2. Using an independentmeasures t test, the only significant differences between thepatients with Dent’s disease and those with IH in anyof these measures during the baseline period was in urine pHand uric acid supersaturation. Urine pH was significantly higherin patients with Dent’s disease than in those with IH(P < 0.03), and supersaturation for uric acid was consequentlylower (P < 0.03). There was no difference between the twogroups in uric acid excretion.
Table 2. Baseline clinical measures in patients with Dent’s disease and IH after 2-wk observation of study diet with no medications
Urinary supersaturation for calcium oxalate was significantlyhigher in the patients with IH (P = 0.05; Table 2), reflectingsmall differences in urinary oxalate, citrate, and volume thatindividually were NS. Two patients with Dent’s disease(patients 6 and 8) and three patients with IH (patients 12,13, and 16) were hyperoxaluric. Patient 9 (with IH) but noneof the patients with Dent’s disease had hypocitraturiaat baseline.
Effects of Treatment on Calcium Excretion
The analysis revealed a significant main effect for treatmenton calcium excretion, no significant effects for group, andno interaction effect. A priori contrasts comparing each drugintervention to baseline revealed a significant lowering ofcalcium excretion (mg/kg per 24 h) relative to baseline aftertreatment with chlorthalidone alone both for patients with Dent’sdisease and those with IH (P < 0.002). With chlorthalidone,calcium excretion fell to normal (<4.0 mg/kg per 24 h) inall but one patient in each group. However, the a priori contrastsrevealed no change in calcium excretion with amiloride alonerelative to baseline. With the combination of amiloride pluschlorthalidone (P < 0.003), the reduction in calcium excretionwas similar to that with chlorthalidone alone.
These results were consistent for calcium excretion expressedas mg/kg per 24 h, mg/24 h, or mg/g creatinine. Compared withthe baseline period, calcium excretion was significantly reducedduring treatment with chlorthalidone in patients with Dent’sdisease or IH whether expressed as mg/kg per 24 h, mg/24 h,or mg/g creatinine (P < 0.003, P < 0.001, P < 0.002,respectively). Similarly, chlorthalidone plus amiloride reducedcalcium excretion relative to baseline by any of the three measures,regardless of patient group (P < 0.002, P < 0.004, P <0.004, respectively). Amiloride alone had no effect on calciumexcretion relative to baseline by any of the three measures.Figure 2 illustrates the results expressed as mg/kg per 24 h.
Figure 2. Calcium excretion expressed as mg/kg per 24 h during the four study periods in the two patient groups. Results are shown as mean ± SE for patients with Dent’s disease (solid squares) and IH (open circles). Significant a priori contrasts indicating differences from the control (baseline) period are indicated by asterisks (*P < 0.01).
Effects of Treatment on Supersaturation Ratios
The a priori contrasts comparing mean supersaturation ratiosfor calcium oxalate with each treatment relative to baselineshowed a reduction when treated with chlorthalidone alone orin combination with amiloride, but the reduction reached traditionallevels of statistical significance for the combination treatmentonly (Figure 3A, P < 0.02). This effect was similar in patientswith Dent’s disease and IH. Mean supersaturation ratiosfor calcium phosphate in patients with Dent’s diseasewere lower during treatment with chlorthalidone (1.56 ±0.17) than at baseline (2.40 ± 0.29), but this did notreach statistical significance (Figure 3B, P = 0.074).
Figure 3. Supersaturation ratios for calcium oxalate (A), calcium phosphate (B), and uric acid (C) during the four study periods in the two patient groups. Results are shown as mean ± SE for patients with Dent’s disease (solid squares) and IH (open circles). (A) The reduction in calcium oxalate supersaturation with chlorthalidone was only significant with combination with amiloride (P < 0.02 a priori contrast comparing treatment to baseline, regardless of patient group). (B) Differences in supersaturation for calcium phosphate during treatment compared with baseline did not reach traditional levels of significance. (C) The fall in uric acid supersaturation was greater in patients with IH than those with Dent’s disease during treatment with chlorthalidone relative to baseline (P < 0.03).
The analysis of supersaturation ratio for uric acid revealeda significant a priori interaction contrast comparing the responseto chlorthalidone relative to baseline for patients with IHand Dent’s disease (P < 0.03). Patients with IH showeda more dramatic decrease in their supersaturation ratios foruric acid than those with Dent’s disease during treatmentwith chlorthalidone. All of the supersaturation ratios for uricacid are well below the upper limit of normal (1.0); thereforethese patients are not at risk for uric acid stones.
Other Effects on Urine Composition
Some comparisons revealed statistically significant effectsof treatment on excretion of citrate and uric acid, and thesedata are shown on Table 3. There was a significant decline inmean citrate excretion relative to baseline, regardless of patientgroup, with chlorthalidone alone, (P < 0.039). Contrary toexpectations, the addition of amiloride to chlorthalidone wasalso associated with a significant decline in mean citrate excretion(P < 0.02). Mean uric acid excretion was somewhat lower thanbaseline with all treatment periods, but this was only significantfor treatment with amiloride (P < 0.03). Mean excretion ofphosphate was generally lower during treatment periods thanat baseline, but the difference was only significant for treatmentwith chlorthalidone (P < 0.02). There were no differencesin oxalate excretion with any of the treatment periods, norwere there differences between patients with Dent’s diseaseand IH in oxalate excretion.
Table 3. Other measurements in which significant effects involving treatment were observed
Twenty-four–hour urinary pH was significantly higher atbaseline in patients with Dent’s disease than in thosewith IH (Table 2; P < 0.03). Urine pH rose significantlyduring treatment with chlorthalidone alone (P < 0.01) andchlorthalidone plus amiloride (P < 0.05) regardless of patientgroup (Table 3). It is possible that this reflects an effectof the thiazide to inhibit carbonic anhydrase (19) or perhapsan effect of hypokalemia (if it occurred) to suppress aldosteroneproduction and thereby reduce the stimulation by aldosteroneof the H+-ATPase in the collecting duct (20).
Analysis of urine volume revealed a main effect for condition,with urine volumes consistently higher in the patients withDent’s disease (P < 0.03). This is consistent withthe common observation of a urinary concentrating defect inDent’s disease (5,8,17). There were no significant differencesin urinary ammonium excretion.
At baseline on a controlled diet, patients with Dent’sdisease had degrees of hypercalciuria comparable to those withIH. Anecdotal reports had indicated that urinary excretion ofcitrate is normal in patients with Dent’s disease andthat excretion of oxalate is usually normal (8,16,17). Our baselinemeasurements indicate that excretion of citrate and oxalatewere similar in Dent’s disease and IH, that hyperoxaluriawas seen no more frequently in the patients with Dent’sdisease than in those with IH, and that none of the patientswith Dent’s disease was hypocitraturic. Occasional casesof hyperuricosuria have been reported in Dent’s disease(16,17), though hypouricemia has not been described. In thisstudy, urinary excretion of uric acid in patients with Dent’sdisease was very similar to that in patients with IH.
The significantly lower supersaturation ratio for uric acidin patients with Dent’s disease at baseline was accountedfor by the significantly higher urinary pH. That uric acid supersaturationfell somewhat more in patients with IH than those with Dent’sdisease during treatment with chlorthalidone is consistent withthe fact that the baseline urinary pH in patients with IH (6.14)was lower than that in patients with Dent’s disease (6.58)and thus closer to the pK for uric acid (5.5). The ClC-5 chloridechannel that is inactivated by mutations in these patients isexpressed in the -intercalated cells of the collecting duct,although most patients with Dent’s disease can acidifythe urine normally when challenged (16,17). Our observationdoes not reflect abnormal buffer excretion, because excretionof ammonium and phosphate were similar in the two groups.
Phosphate excretion was slightly lower during all treatmentperiods, and this was significant for treatment with chlorthalidone.Since these patients should have been at steady state duringthese measurements, it seems unlikely that this would reflectdiuretic-induced changes in blood volume. It is possible thata small rise in serum calcium could have suppressed serum levelsof PTH or 1,25-dihydroxyvitamin D, leading to a reduction inbone resorption or intestinal absorption of phosphate, but wecannot answer this question without measurements of serum levels.
Urinary calcium excretion was reduced to virtually identicaldegrees in the patients with Dent’s disease and thosewith IH. This is not surprising, given that the ClC-5 chloridechannel is not expressed in the thiazide-sensitive distal convolutedtubule (6). Amiloride was ineffective either alone or in combinationwith chlorthalidone. This was not a consequence of ClC-5 inactivation,because it was as ineffective in patients with IH as in thosewith Dent’s disease. Other reports on the effectivenessof amiloride on urinary calcium excretion in humans, using dosessimilar to those in this study, have described a reduction incalcium excretion in only a minority of calcium stone-formers(13), and only a modest effect to augment the hypocalciuriceffect of thiazides (14). Costanzo and Weiner (18) have shownin dogs that the anticalciuretic effect of maximal doses ofamiloride is much smaller than that of chlorothiazide, althoughthe effects of the two diuretics are additive. In clinical practice,the major practical value of adding amiloride to a thiazidein a hypercalciuric stone-forming patient is to ameliorate hypokalemia.Even this effect, however, is not necessarily associated witha moderation of hypocitraturia, as demonstrated by Leppla etal. (13) and by our data (Table 3).
Despite the significant correction of hypercalciuria by chlorthalidonein both patient groups, the fall in supersaturation ratios forcalcium oxalate was less impressive, primarily because of agenerally lower mean citrate excretion. Nevertheless, in patientswith Dent’s disease, supersaturation ratio for calciumphosphate fell by 35% — despite a rise in urinary pH —and supersaturation ratio for calcium oxalate fell by 25%. Stonesin patients with Dent’s disease are composed of calciumoxalate, calcium phosphate, or a combination of the two (5,16,17).Thiazides have been shown to reduce the rate of calcium stonerecurrence in patients with IH (10,11), and we now show thatthe effects on urinary measures of stone risk are similar inpatients with Dent’s disease. Thus, it seems justifiedto treat hypercalciuric patients with Dent’s disease witha thiazide diuretic if they have had recurrent stones. It isnot clear whether hypercalciuria is the cause of renal failurein patients with Dent’s disease, and thus we do not yetknow whether therapy to reduce calcium excretion would be ofany benefit in protecting renal function in these patients.
Acknowledgments
The authors are grateful to Drs. Fred Coe and Craig Langmanfor helpful advice on the design of the study and to Ms. NancyNewman for assistance with the statistical analyses. This studywas supported by an award from the NIDDK (RO1 DK46838) to SJS.A preliminary report of these results was presented at the 31stAnnual Meeting of the American Society of Nephrology, October27, 1998, in Philadelphia, PA.
Hoopes RR, Hueber PA, Reid RJ, Braden GL, Goodyer PR, Melnyk AR, Midgley JP, Moel DI, Neu AM, VanWhy SK Scheinman SJ: CLCN5 chloride-channel mutations in six new North American families with X-linked nephrolithiasis: Kidney International 54: 698–705, 1998[CrossRef][Medline]
Lloyd SE, Pearce SHS, Fisher SE, Steinmeyer K, Schwappach B, Scheinman SJ, Harding B, Bolino A, Devoto M, Goodyer P, Rigden SPA, Wrong O, Jentsch TJ, Craig IW Thakker RV: A common molecular basis for three inherited kidney stone diseases. Nature 379: 445–449, 1996[CrossRef][Medline]
Raja K, Hoopes RR, Jr., Blowey D, Haas S, Katz A Somers MJG, Scheinman SJ: Mutation analysis of CLCN5 in X-linked nephrolithiasis (Dent’s disease). Journal of the American Society of Nephrology (Abstract), 1999
Lloyd SE, Gunther W, Pearce SHS, Thomson A, Bianchi ML, Bosio M, Craig IW, Fisher SE, Scheinman SJ, Wrong O, Jentsch TJ Thakker RV: Characterisation of renal chloride channel, CLCN5, mutations in hypercalciuric nephrolithiasis (kidney stones) disorders. Human Molecular Genetics 6: 1233–1239, 1997[Abstract/Free Full Text]
Scheinman SJ: X-linked hypercalciuric nephrolithiasis: Clinical syndromes and chloride channel mutations. Kidney International 53: 3–17, 1998[CrossRef][Medline]
Devuyst O, Christie PT, Courtoy PJ, Beauwens R Thakker RV: Intra-renal and subcellular distribution of the human chloride channel. CLC-5 reveals a pathophysiological basis for Dent’s disease. Human Molecular Genetics 8: 247–257, 1999[Abstract/Free Full Text]
Scheinman SJ, Thakker RV: X-linked nephrolithiasis/Dent’s disease and mutations in the ClC-5 chloride channel, in: Genetic Aspects of Osteoporosis and Metabolic Bone Disease (vol in press), edited by MJ Econs, Totowa NJ, Humana Press, 1999
Reinhart SC, Norden AGW, Lapsley M, Thakker RV, Pang J, Moses AM, Frymoyer PA, Favus MJ, Hoepner JA Scheinman SJ: Characterization of carrier females and affected males with X-linked recessive nephrolithiasis. J Am Soc Nephrol 5: 1451–1461, 1995[Abstract]
Coe FL, Parks JH, Bushinsky DA, Langman CB Favus MJ: Chlorthalidone promotes mineral retention in patients with idiopathic hypercalciuria. Kidney Int 33: 1140–1146, 1988[Medline]
Coe FL: Treated and untreated recurrent calcium nephrolithiasis in patients with idiopathic hypercalciuria, hyperuricosuria, or no metabolic disorder. Ann Intern Med 87: 404–410, 1977
Ettinger B, Citron JT, Livermore B Dolman LI: Chlorthalidone reduces calcium oxalate calculous recurrence but magnesium hydroxide does not. J Urol 139: 679–684, 1988[Medline]
Nicar MJ, Hill K Pak CY: Inhibition by citrate of spontaneous precipitation of calcium oxalate in vitro. J Bone Miner Res 2: 215–220, 1987[Medline]
Leppla D, Browne R, Hill K Pak CY: Effect of amiloride with or without hydrochlorothiazide on urinary calcium and saturation of calcium salts. J Clin Endocrinol Metab 57: 920–924, 1983[Abstract]
Alon U, Costanzo LS Chan JC: Additive hypocalciuric effects of amiloride and hydrochlorothiazide in patients treated with calcitriol. Miner Electrolyte Metab 10: 379–386, 1984[Medline]
Asplin JR, Bushinsky DA, Singharetnam W, Riordon D, Parks JH Coe FL: Relationship between supersaturation and crystal inhibition in hypercalciuric rats. Kidney International 51: 640–645, 1997[Medline]
Frymoyer PA, Scheinman SJ, Dunham PB, Jones DB, Hueber P Schroeder ET: X-linked recessive nephrolithiasis with renal failure: N Engl J Med 325: 681–686, 1991[Abstract]
Wrong O, Norden AGW Feest TG: Dent’s disease: a familial proximal renal tubular syndrome with low-molecular-weight proteinuria, hypercalciuria, nephrocalcinosis, metabolic bone disease, progressive renal failure, and a marked male predominance. Quarterly Journal of Medicine 87: 473–493, 1994[Abstract/Free Full Text]
Costanzo LS, Weiner IM: Relationship between clearances of Ca and Na: effect of distal diuretics and PTH. Am J Physiol230: 67–73, 1976
Martinez-Maldonado M, Cordova HR: Cellular and molecular aspects of the renal effects of diuretic agents. Kidney International 38: 632–41, 1990[Medline]
O’Neil RG, Hayhurst RA: Sodium-dependent modulation of the renal Na-K-ATPase: influence of mineralocorticoids on the cortical collecting duct. J Membr Biol 85: 169–79, 1985[CrossRef][Medline]
Received for publication September 17, 2001.
Accepted for publication July 29, 2002.
This article has been cited by other articles:
M. Ludwig, B. Utsch, and L. A. H. Monnens Recent advances in understanding the clinical and genetic heterogeneity of Dent's disease
Nephrol. Dial. Transplant.,
October 1, 2006;
21(10):
2708 - 2717.
[Full Text][PDF]
N. Besbas, F. Ozaltin, N. Jeck, H. Seyberth, and M. Ludwig CLCN5 mutation (R347X) associated with hypokalaemic metabolic alkalosis in a Turkish child: an unusual presentation of Dent's disease
Nephrol. Dial. Transplant.,
July 1, 2005;
20(7):
1476 - 1479.
[Full Text][PDF]
Department of Pediatrics, Yale University School of Medicine, New Haven, Connecticut; and #Department of Medicine, University of Chicago Pritzker School of Medicine, Chicago, Illinois.
Top
Abstract
Introduction
-intercalated cells of the human nephron (6). 
11 yr old. Patients were randomized at entry to receive one of six potential protocols with different sequences for these three treatment periods. At the end of the baseline period and each treatment period, two successive 24-h urine collections were obtained. Treatment periods were separated by a 1-wk washout period off diuretics (Figure 1). 
