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Secretory-Defect Distal Renal Tubular Acidosis Is Associated with Transporter Defect in H⁺-ATPase and Anion Exchanger-1

Jin Suk Han^*, Gheun-Ho Kim, Jin Kim, Un Sil Jeon, Kwon Wook Joo^¶, Ki Young Na^*, Curie Ahn^*, Suhnggwon Kim^*, Sang Eun Lee^|| and Jung Sang Lee^*

*Department of Internal Medicine, Seoul National University, Clinical Research Institute of Seoul National University Hospital, Seoul, Korea; Department of Internal Medicine, Hallym University Hangang Sacred Heart Hospital, Seoul, Korea; Department of Anatomy, Catholic University, Seoul, Korea; Department of Internal Medicine, Gyeong-sang National University, Chinju, Korea; ^¶Department of Internal Medicine, Gachon Medical School, Incheon, Korea; ^||Department of Urology, Seoul National University, Seoul, Korea.

Correspondence to: Dr. Jung Sang Lee, Department of Internal Medicine, Seoul National University, Research Institute of Seoul National University Hospital, 28, Yongun-dong, Chongno-gu, Seoul, 110-744, South Korea. Phone: +82-2-760-2265; Fax : +82-2-742-9031; E-mail : jsleemd{at}plaza.snu.ac.kr

	Abstract

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ABSTRACT. Recent progress in molecular physiology has permitted us to understand pathophysiology of various channelopathies at a molecular level. The secretion of H⁺ from -intercalated cells is mediated by apical plasma membrane H⁺-ATPase and basolateral plasma membrane anion exchanger-1 (AE1). Studies have demonstrated the lack of H⁺-ATPase immunostaining in the intercalated cells in a few patients with distal renal tubular acidosis (dRTA). Mutations in H⁺-ATPase and AE1 gene have recently been reported to cause dRTA. This study extends the investigation of the role of transporter defect in dRTA by using immunohistochemical methods. Eleven patients with hyperchloremic metabolic acidosis were diagnosed functionally to have secretory-defect dRTA: urine pH >5.5 during acidemia, normokalemia or hypokalemia, and urine-to-blood pCO₂ <25 mmHg during bicarbonaturia. Renal biopsy tissue was obtained from each patient, and immunohistochemistry was carried out using antibodies to H⁺-ATPase and AE1. For comparison, renal tissues from the patients who had no evidences of distal acidification defect by functional studies were used: four with glomerulopathy or tubulointerstitial nephritis (disease controls) and three from nephrectomized kidneys for renal cell carcinoma (normal controls). The H⁺-ATPase immunoreactivity in -intercalated cells was almost absent in all of the 11 patients with secretory-defect dRTA. In addition, 7 of 11 patients with secretory-defect dRTA were accompanied by negative AE1 immunoreactivity. In both disease controls and normal controls, the immunoreactivity of H⁺-ATPase and AE1 was strong in -intercalated cells. In conclusion, significant defect in acid-base transporters is the major cause of secretory-defect dRTA.

	Introduction

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Renal tubular acidosis comprises a diverse group of tubular disorders that are characterized by an impairment of urinary acidification. Urinary acidification can be divided into proximal and distal categories on the basis of which nephron segment is involved in H⁺ secretion and HCO₃^- reabsorption. The proximal tubule is the major site for reabsorption of filtered HCO₃^-, and the distal nephron, primarily the collecting duct, is responsible for reabsorption of the remaining 10 to 20% of filtered HCO₃^- and for elimination of excess H⁺ (1).

The importance of the apical H⁺-ATPase and basolateral anion exchanger-1 (AE1) in distal acidification is well established (2). There is evidence that -intercalated cells also have an apical H⁺-K⁺-ATPase (3) that may account for a significant fraction of HCO₃^- transport (4). Functionally, normal distal acidification requires an impermeant luminal membrane that is capable of sustaining large pH gradients, a lumen-negative potential difference in the cortical collecting duct supporting both H⁺ and K⁺ secretion in this segment, and a rate of H⁺ secretion by the -intercalated cells of the cortical and medullary collecting ducts (5). Therefore, distal renal tubular acidosis (dRTA) has been functionally classified into gradient (backleak), voltage-dependent, and secretory-defect on the basis of the deranged physiologic mechanisms of urinary acidification (6). In principle, the secretory-defect dRTA should be caused by an impairment of distal H⁺ secretion, which may arise from reduction in the number of intercalated cells, reduction in the quantity of H⁺-ATPase and/or H⁺-K⁺-ATPase in the intercalated cells, or an abnormal distribution of proton pump(s) with a reduced quantity at the apical membrane (5).

We and others have demonstrated the lack of H⁺-ATPase immunostaining in the intercalated cells in a few patients with secretory-defect dRTA (7–10). Mutations in H⁺-ATPase (11) and AE1 gene (12–16) have recently been reported to cause dRTA. Here, we extend our investigation on the role of acid-base transporter defect in the patients with secretory-defect dRTA by using immunohistochemical methods. This study suggests that reduction in the quantity of H⁺-ATPase and AE1 may be the major cause of functionally diagnosed secretory-defect dRTA.

	Materials and Methods

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Patients
Diagnosis and classification of renal tubular acidosis were done by the functional tests described below. Eleven patients were enrolled in the group of secretory-defect dRTA. The causes of dRTA were idiopathic, tubulointerstitial nephropathies, and autoimmune disorders such as Sjogren’s syndrome. Four patients with intrinsic renal diseases but without any defect in urinary acidification were enrolled in disease controls. Three patients who underwent surgical nephrectomy due to renal cell carcinoma served as normal controls. For immunohistochemistry, percutaneous renal biopsy specimens were obtained from the group of secretory-defect dRTA and disease controls. Normal tissue fractions of the nephrectomized kidneys were also examined from normal controls.

Physiologic Tests for Urinary Acidification
To evaluate urinary acidification, we performed short-term ammonium chloride loading, furosemide test, and sodium bicarbonate loading (17), as described below. The ammonium chloride loading test was omitted in cases of overt acidemia (plasma HCO₃^- <18 mmol/L). Urine pH was measured using a pH meter (Beckman, Fullerton, CA), and urine and blood pCO₂ were measured by a blood gas analyzer (Nova, Waltham, MA). Serum and urine electrolytes and creatinine were measured on an autoanalyzer (Beckman, Fullerton, CA). Urine ammonium was determined by the enzymatic method (18).

In the short-term ammonium chloride loading test, urine was collected under mineral oil at 2-h intervals from 4 to 8 h after the administration of NH₄Cl at a dose of 0.2 g/kg body wt. Blood samples were also taken at the end of each 2-h urine collection to ensure that plasma the bicarbonate level decreased to 20 mmol/L or less. For the furosemide test, urine was collected at 2-h intervals from 4 to 6 h after an oral dose (1 mg/kg body weight) of furosemide. To increase the sensitivity of the test by ensuring a state of sodium avidity, 1 mg of fludrocortisone was administered orally the evening before the testing. In the bicarbonate loading test, 2.75% NaHCO₃ solution was infused intravenously at a rate of 4 ml/kg per h. Urine and blood samples were taken at 2-h intervals until plasma bicarbonate concentration reached 26 mmol/L. The values of urine-to-blood pCO₂ gradient and fractional excretion of bicarbonate were calculated when urine pH was raised to 7.5.

Immunohistochemistry from Renal Tissues
The renal tissues from the dRTA patients, disease controls and normal controls were preserved in periodate-lysine-paraformaldehyde. The fixed tissues were dehydrated and embedded in polyester wax, and sections were cut to 4-µm thickness and mounted on gelatin-coated glass slides. The sections were dewaxed with xylene and ethanol and were treated with methanolic H₂O₂ for 30 min after rinsing under tap water. Before incubation with primary antibodies, the sections were permeabilized by incubation for 15 min in 0.5% Triton X-100 in phosphate-buffered saline (PBS), and then blocked with normal goat serum diluted 1:10 in PBS for 15 min. Subsequently, the sections were incubated overnight at 4°C with rabbit polyclonal antibodies to the 70-kd catalytic subunit of the vacuolar H⁺-ATPase (kindly provided by Dr. Dennis Stone, University of Texas Southwestern, Dallas, TX) and erythrocyte Cl^-/HCO₃^- exchanger, AE1 (kindly provided by Dr. Philip S. Low, Purdue University, West Lafayette, IL), a mouse monoclonal antibody (7C6) raised against chicken carbonic anhydrase II (kindly provided by Dr. Paul Linser, Whitney Marine Laboratory, University of Florida, Gainesville, FL), and a mouse monoclonal antibody to Na⁺-K⁺-ATPase 1 subunit (Upstate Biotechnology, Lake Placid, NY). The sections were rinsed in PBS and incubated with the biotinylated secondary antibody for 60 min and subsequently with the Vectastain ABC reagent for 60 min. After being rinsed with 0.1 M Tris buffer, the sections were incubated with a mixture of 0.05% 3.3'-diaminobenzidine and 0.033% H₂O₂ for 1 to 2 min at room temperature. After being rinsed with Tris buffer again, the sections were counterstained with hematoxylin and examined with light microscopy.

	Results

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Table 1 shows the results of urinary acidification tests from the patients and controls. In normal controls, as expected, urine pH was low with NH₄Cl loading and urine-to-blood pCO₂ gradient was large with NaHCO₃ loading. In disease controls, who had glomerulopathy or tubulointerstitial nephritis but without evidences of acidification defect, urine pH was below 5.3 during acidemia, which was induced by short-term NH₄Cl loading, indicating intact distal acidification.

Renal biopsy tissue was obtained from each patient, and immunohistochemistry was carried out using antibodies to H⁺-ATPase, AE1, carbonic anhydrase II, and Na⁺-K⁺-ATPase 1 subunit. Renal biopsy specimens from the disease controls were also used for comparison. We also examined three different normal tissue sections from nephrectomized kidneys for renal cell carcinoma (normal controls).

Figure 1 shows H⁺-ATPase immunohistochemistry in connecting tubule and cortical collecting duct from the normal controls, disease controls, and dRTA patients. In both normal controls and disease controls, the immunostaining of H⁺-ATPase was strongly positive on the apical membranes of -intercalated cells. However, the secretory-defect dRTA patients revealed absolute decrease in immunostaining of H⁺-ATPase along the connecting tubule and collecting duct.

View larger version (89K): [in this window] [in a new window] [as a PowerPoint slide]   Figure 1. Differential interference contrast (DIC) micrographs of renal cortex from normal controls (A and B), disease controls (C and D), and secretory-defect distal renal tubular acidosis (dRTA) patients (E and F) illustrating immunostaining for H+-ATPase. In normal controls, numerous intercalated cells with apical (arrows) and diffuse (open arrow) H+-ATPase immunoreactivity are observed in the connecting tubule (CNT) and cortical collecting duct (CCD). In disease controls, intercalated cells with strong H+-ATPase immunoreactivity (arrows) are seen in the CNT and CCD. In secretory-defect dRTA patients, H+-ATPase–labeled intercalated cells are decreased both in number and in intensity of immunoreactivity for H+-ATPase along the CNT and CCD. PT, proximal tubule. Magnification, x400.

View larger version (96K): [in this window] [in a new window] [as a PowerPoint slide]   Figure 2. DIC micrographs illustrating immunostaining for H+-ATPase in the PT from normal control (A), disease control (B), and a secretory-defect dRTA patient (C). Strong positive immunoreactivity of H+-ATPase in normal and disease controls is observed in the PT. In the secretory-defect dRTA patient, who has combined defect in proximal acidification, H+-ATPase immunoreactivity is decreased in the PT compared with controls. Magnification, x400.

View larger version (115K): [in this window] [in a new window] [as a PowerPoint slide]   Figure 3. DIC micrographs of renal cortex from normal control (A), disease control (B), and secretory-defect dRTA patients (C and D) illustrating immunostaining for anion exchanger-1 (AE1). In normal and disease controls, a lot of intercalated cells (arrows) with basolateral immunostaining for AE1 are seen in the CNT and CCD. In secretory-defect dRTA patients, only a few intercalated cells weakly labeled with AE1 are seen in the connecting tubule and collecting ducts. Magnification, x400.

View larger version (84K): [in this window] [in a new window] [as a PowerPoint slide]   Figure 4. DIC micrographs of renal cortex from normal control (A and B), disease control (C and D), and a secretory-defect dRTA patient (E and F) illustrating immunostaining for carbonic anhydrase II (CA II) in the CNT (A, C, and E) and CCD (B, D, and F). In normal and disease control, intercalated cells (arrows) in both the CNT and CCD exhibit strong immunoreactivity. In the secretory-defect dRTA patient, however, immunostaining for CA II both in CNT and CCD is markedly decreased in intensity. Magnification, x400.

View larger version (95K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 5. DIC micrographs of renal cortex from normal control (A), disease control (B), and a secretory-defect dRTA patient (C) illustrating immunostaining for Na-K-ATPase 1 subunit. Positive immunoreactivity of Na-K-ATPase in normal and disease controls is observed in the distal convoluted tubules and thick ascending limbs (*). The secretory-defect dRTA patient also shows strong immunostaining for Na-K-ATPase in both nephron segments. Magnification, x400.

	Discussion

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The existence of secretory-defect dRTA has been reasonably well characterized in patients with different diseases causing acquired dRTA (22). Derangements of collecting duct function determined genetically (e.g., hereditary dRTA), associated with structural abnormalities (e.g., medullary sponge kidney), or immunologically mediated (e.g., Sjogren’s syndrome) could all interfere with the integrity of the proton pump secretory apparatus (22). Our dRTA patients were functionally diagnosed on the basis of the following results to have a secretory defect. First, urine pH was not lowered below 5.5, not only during acidemia, but also after stimulation of sodium-dependent distal acidification by the administration of furosemide. Second, the urine pCO₂ measured after bicarbonate loading did not increase normally, reflecting that the rate of collecting duct H⁺ secretion is reduced.

In the collecting duct, H⁺-ATPase is likely responsible for much of the H⁺ secretion that takes place in this segment (23). Therefore, the secretory-defect dRTA could be due to any alterations causing an impairment of the collecting duct acidification by primarily interfering with the H⁺-ATPase. Cohen et al. (7) first demonstrated absence of H⁺-ATPase staining in collecting duct cells from a renal biopsy specimen from a patient with secretory-defect dRTA and Sjogren’s syndrome. They found the presence on electron microscopy of cells with typical ultrastructural features of intercalated cells, and they suggested that the distal acidification defect was due to the absence of intact H⁺-ATPase rather than the selective loss of -intercalated cells. We have also reported that a patient with idiopathic hypokalemic dRTA (Albright’s disease) had absence of H⁺-ATPase staining in the intercalated cells (10). Taken together with the results from our current study, it is strongly indicated that lack of H⁺-ATPase in the intercalated cells of the collecting duct may be the chief cellular mechanism responsible for the secretory-defect dRTA.

We found that not only H⁺-ATPase but also AE1 immunostaining were absent in the -intercalated cells in the majority of our secretory-defect dRTA patients, suggesting failure of -intercalated cells to express both the H⁺-ATPase and AE1 proteins. Although the reason is unclear, few -intercalated cells were noted in our biopsy tissue. Therefore, we could not describe any changes in the -intercalated cells. In addition, the immunoreactivity for both H⁺-ATPase and AE1 was so weak in the secretory-defect dRTA patients that we could not analyze further on subtype defects in the intercalated cells.

Bastani and associates (8,9) previously examined kidney biopsies from two patients with Sjogren’s syndrome, and neither patient showed any immunostaining of intercalated cells with the antibodies against H⁺-ATPase and AE1. The ultrastructural presence of intercalated cells and the absence of discernible staining for H⁺-ATPase and AE1 suggest that the defect in proton secretion may represent a defect involving the assembly of at least two of the ion transport pumps that are essential for the normal maintenance of acid-base homeostasis by the intercalated cells (8). Consistent with this view, we found that CA II immunostaining in the intercalated cells of the connecting tubule and cortical collecting duct was markedly decreased in the secretory-defect dRTA patients. The parallel decrease in H⁺-ATPase and CA II expression might be explained by the fact that the H⁺-secreting process is accelerated by cytosolic or membrane-associated carbonic anhydrase in most H⁺-secreting cells (24).

Deficiency of CA II is an autosomal recessive disorder producing a distinctive syndrome of renal tubular acidosis, osteopetrosis, cerebral calcification, and mental retardation (25), and most patients with CA II deficiency syndrome have both proximal and distal components to the renal tubular acidosis (26). Three patients from our current study were diagnosed on the basis of high fractional excretion of bicarbonate to have combined proximal and distal acidification defect. However, we could not find any clinical evidence for CA II deficiency syndrome in these patients. Our immunostaining for CA II in the proximal tubule was weakly positive in both the patients and controls. Although we found negative or trace H⁺-ATPase immunostaining in proximal tubule cells in three dRTA patients, there was no clear association between the lack of proximal tubule H⁺-ATPase immunoreactivity and the presence of combined proximal acidification defect.

The Na⁺-K⁺-ATPase, located in the basolateral membranes of renal tubular epithelial cells, also has a role in pathophysiology of urinary acidification defects (27), because H⁺-ATPase activity can be secondarily affected if Na⁺-K⁺-ATPase is altered (28). In this study, intercalated cells did not show enough Na⁺-K⁺-ATPase immunostaining to compare the patients with the controls. The distal tubules, on the other hand, showed strong Na⁺-K⁺-ATPase immunoreactivity in both the patients and the controls. These findings seemed compatible with the results of Na⁺-K⁺-ATPase activity measured in individual segments of the nephron (29). We believe that intrinsic failure of H⁺-ATPase would be associated with features of dRTA.

The pathogenic mechanisms causing the absence of immunostaining for H⁺-ATPase and/or AE1 remain elusive. Although the nature of the defects is unknown, point mutations producing abnormal acid-base transporters may underlie primary dRTA in adults. A variety of tubulointerstitial disease may produce secondary dRTA. Conceivably, the inflammatory process prevents the normal assembly and/or insertion of H⁺-ATPase into the apical plasma membrane. However, the renal tissue from our dRTA patients revealed only occasional findings of interstitial infiltration, and thus it appears that other mechanisms may play a role in the development of the acidification defect. We postulate existence of as-yet-unknown renal molecules that may affect synthesis, trafficking, or degradation of acid-base transporter protein.

Finally, most of our dRTA patients were hypokalemic. Hypokalemia is presumably due to increased distal potassium secretion, possibly mediated by secondary hyperaldosteronism and increased distal delivery of sodium or a defect in H⁺-K⁺-ATPase (6,30). Unfortunately, the lack of antibodies prevented us from testing the possible role of a deficiency of H⁺-K⁺-ATPase as the mechanism underlying hypokalemic dRTA. Further studies are needed to elucidate a role for H⁺-K⁺-ATPase in the pathogenesis of hypokalemic dRTA.

	Acknowledgments

 
This work is supported by the Grant 97-N1–02-04-A-05 from Ministry of Science and Technology of Korea and by the Brain Korea 21 Project from Korea Research Foundation. The authors are indebted to Young-Hee Kim and So-Young Kim for technical assistance.

	References

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1. Sabatini S, Kurtzman NA: Overall acid-base regulation by the kidney.In Seldin DW, Giebisch G, (eds.): Regulation of Acid-Base Balance. New York, Raven Press, 1989,pp 185–210
2. Gluck SL, Iyori M, Holliday LS, Kostrominova T, Lee BS: Distal urinary acidification from Homer Smith to the present. Kidney Int 49: 1660–1664, 1996[Medline]
3. Bastani B: Colocalization of H-ATPase and H, K-ATPase immunoreactivity in the rat kidney. J Am Soc Nephrol 5: 1476–1482, 1995[Abstract]
4. Gifford JD; Rome L; Galla JH: H⁺-K⁺-ATPase activity in rat collecting duct segments. Am J Physiol 262: 692–F695, 1992
5. Bastani B, Gluck SL: New insights into the pathogenesis of distal renal tubular acidosis. Miner Electrolyte Metab 22: 396–409, 1996[Medline]
6. Kurtzman NA: Disorders of distal acidification. Kidney Int 38: 720–727, 1990[Medline]
7. Cohen EP, Bastani B, Cohen MR, Kolner S, Hemken P, Gluck SL: Absence of H⁺-ATPase in cortical collecting tubules of a patient with Sjogren’s syndrome and distal renal tubular acidosis. J Am Soc Nephrol 3: 264–271, 1992[Abstract]
8. DeFranco PE, Haragsim L, Schmitz PG, Bastani B: Absence of vacuolar H⁺-ATPase pump in the collecting duct of a patient with hypokalemic distal renal tubular acidosis and Sjogren’s syndrome. J Am Soc Nephrol 6: 295–301, 1995[Abstract]
9. Bastani B, Haragsim L, Gluck S, Siamopoulos KC: Lack of H-ATPase in distal nephron causing hypokalaemic distal RTA in a patient with Sjogren’s syndrome (letter). Nephrol Dial Transplant 10: 908–909, 1995[Free Full Text]
10. Joo KW, Jeon US, Han JS, Ahn C, Kim S, Lee JS, Kim GH, Cho YS, Kim YH, Kim J: Absence of H⁺-ATPase in the intercalated cells of renal tissues in classic distal renal tubular acidosis. Clin Nephrol 49: 226–231, 1998[Medline]
11. Karet FE, Finberg KE, Nelson RD, Nayir A, Mocan H, Sanjad SA, Rodriguez-Soriano J, Santos F, Cremers CW, Di Pietro A, Hoffbrand BI, Winiarski J, Bakkaloglu A, Ozen S, Dusunsel R, Goodyer P, Hulton SA, Wu DK, Skvorak AB, Morton CC, Cunningham MJ, Jha V, Lifton RP: Mutations in the gene encoding B1 subunit of H⁺-ATPase cause renal tubular acidosis with sensorineural deafness. Nat Genet 21: 84–90, 1999[CrossRef][Medline]
12. Bruce LJ, Cope DL, Jones GK, Schofield AE, Burley M, Povey S, Unwin RJ, Wrong O, Tanner MJ: Familial distal renal tubular acidosis is associated with mutations in the red cell anion exchanger (Band 3, AE1) gene. J Clin Invest 100: 1693–1707, 1997[Medline]
13. Jarolim P, Shayakul C, Prabakaran D, Jiang L, Stuart-Tilley A, Rubin HL, Simova S, Zavadil J, Herrin JT, Brouillette J, Somers MJ, Seemanova E, Brugnara C, Guay-Woodford LM, Alper SL : Autosomal dominant distal renal tubular acidosis is associated in three families with heterozygosity for the R589H mutation in the AE1 (band 3) Cl^-/HCO₃^- exchanger. J Biol Chem 273: 6380–6388, 1998[Abstract/Free Full Text]
14. Karet FE, Gainza FJ, Gyory AZ, Unwin RJ, Wrong O, Tanner MJ, Nayir A, Alpay H, Santos F, Hulton SA, Bakkaloglu A, Ozen S, Cunningham MJ, di Pietro A, Walker WG, Lifton RP: Mutations in the chloride-bicarbonate exchanger gene AE1 cause autosomal dominant but not autosomal recessive distal renal tubular acidosis. Proc Natl Acad Sci U S A 95: 6337–6342, 1998[Abstract/Free Full Text]
15. Tanphaichitr VS, Sumboonnanonda A, Ideguchi H, Shayakul C, Brugnara C, Takao M, Veerakul G, Alper SL: Novel AE1 mutations in recessive distal renal tubular acidosis. Loss-of-function is rescued by glycophorin A. J Clin Invest 102 21732179, 1998[Medline]
16. Vasuvattakul S, Yenchitsomanus PT, Vachuanichsanong P, Thuwajit P, Kaitwatcharachai C, Laosombat V, Malasit P, Wilairat P, Nimmannit S: Autosomal recessive distal renal tubular acidosis associated with Southeast Asian ovalocytosis. Kidney Int 56: 1674–1682, 1999[CrossRef][Medline]
17. Lash JP, Arruda JAL: Laboratory evaluation of renal tubular acidosis. Clin Lab Med 13: 117–129, 1993[Medline]
18. Mondaz A, Ehrlich GE, Seegmiller JE: An enzymatic determination of ammonia in biological fluids. J Lab Clin Med 66: 526–531, 1965[Medline]
19. Batlle DC, Hizon M, Cohen E, Gutterman C, Gupta R: The use of the urinary anion gap in the diagnosis of hyperchloremic metabolic acidosis. N Engl J Med 318: 594–599, 1988[Abstract]
20. Kim GH, Han JS, Kim YS, Joo KW, Kim S, Lee JS: Evaluation of urine acidification by urine anion gap and urine osmolal gap in chronic metabolic acidosis. Am J Kidney Dis 27: 42–47, 1996[Medline]
21. Batlle DC: Segmental characterization of defects in collecting tubule acidification. Kidney Int 30: 546–54, 1986[Medline]
22. Batlle D, Flores G: Underlying defects in distal renal tubular acidosis: new understandings. Am J Kidney Dis 27: 896–915, 1996[Medline]
23. Kleinman JG: Proton ATPases and urinary acidification. J Am Soc Nephrol 5: S6–11, 1994[Abstract]
24. Hamm LL, Alpern RJ: Cellular mechanisms of renal tubular acidification.In: The Kidney. Physiology & Pathophysiology, 3^rd ed., edited by Seldin DW, and Giebisch G, Philadelphia, Lippincott Williams & Wilkins, 2000,pp 1935–1979
25. Roth DE, Venta PJ, Tashian RE, Sly WS: Molecular basis of human carbonic anhydrase II deficiency. Proc Natl Acad Sci USA 89: 1804–1808, 1992[Abstract/Free Full Text]
26. Sly WS, Whyte MP, Sundaram V, Tashian RE, Hewett-Emmett D, Guibaud P, Vainsel M, Baluarte HJ, Gruskin A, Al-Mosawi M: Carbonic anhydrase II deficiency in 12 families with the autosomal recessive syndrome of osteopetrosis with renal tubular acidosis and cerebral calcification. N Engl J Med 313: 139–145, 1985[Abstract]
27. Mujais SK: Transport enzymes and renal tubular acidosis. Semin Nephrol 18: 74–82, 1998[Medline]
28. Sabatini S: Experimental studies in distal urinary acidification: bringing the bedside to the bench. Semin Nephrol 19: 188–194, 1999[Medline]
29. Garg LC, Knepper MA, Burg MB: Mineralocorticoid effects on Na-K-ATPase in individual nephron segments. Am J Physiol 240: F536–544, 1981[Abstract/Free Full Text]
30. Smulders YM, Frissen PHJ, Slaats EH, Silberbusch J: Renal tubular acidosis. Pathophysiology and diagnosis. Arch Intern Med 156: 1629–1636, 1996

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This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Han, J. S. Articles by Lee, J. S. Search for Related Content PubMed PubMed Citation Articles by Han, J. S. Articles by Lee, J. S.