 |
||||
| 2007 JASN IMPACT FACTOR 7.111 | HOME AUTHOR INFO EDITORIAL BOARD SUBSCRIBE FEEDBACK ALERTS HELP | |||
| CURRENT ISSUE | ARCHIVES | JASN Express | ONLINE SUBMISSION | |
|
||||
| 2007 JASN IMPACT FACTOR 7.111 | HOME AUTHOR INFO EDITORIAL BOARD SUBSCRIBE FEEDBACK ALERTS HELP | |||
| CURRENT ISSUE | ARCHIVES | JASN Express | ONLINE SUBMISSION | |
*Renal Section, Department of Medicine, Department of Pathology, and the Harry B. and Aileen Gordon Diabetes Research Laboratory, Molecular Diabetes and Metabolism Section, Department of Pediatrics, Baylor College of Medicine, Houston, Texas.
Correspondence to Dr. David Sheikh-Hamad, Renal Section, Department of Medicine, Baylor College of Medicine, 6535 Fannin, MS F505, Houston, TX 77030. Phone: (713) 790-4696; Fax: (713) 790-3666; E-mail: Sheikh{at}bcm.tmc.edu
 |
Abstract |
|---|
 Top Abstract IntroductionMaterials MethodsResultsDiscussionReferences |
|---|
|
Introduction |
|---|
|
TopAbstractIntroductionMaterials MethodsResultsDiscussionReferences |
|---|
In addition, hypertonicity induces a number of heat shock proteins (osmotic shock protein 94; heat shock protein 110 [HSP110]; heat shock protein 70 [HSP70]; and 
B-crystallin), which appear early in the adaptive response to hypertonicity and may thus protect macromolecules until the accumulation of organic osmolytes is accomplished (4–7). The accumulation of organic osmolytes and induction of HSP70 under hypertonic conditions are regulated predominantly at the transcriptional level (3,8–11) via osmotic response elements (ORE) (12), known also as tonicity-responsive enhancers (TonE) (9) and ORE-binding protein (OREBP) (13), an identical protein to TonE-binding protein (TonEBP) (9) and nuclear factor of activated T lymphocyte 5 (NFAT5) (14). The induction of these genes by hypertonicity is a general adaptive mechanism observed in a wide variety of mammalian cells (15).
Cyclosporine A (CsA) is used for immunosuppression after organ transplantation and in patients with autoimmune diseases. Its use has been associated with significant nephrotoxicity, with two major patterns developing in humans: a reversible acute renal failure attributable to constriction of afferent arterioles of the glomeruli with resultant ischemia, and a chronic nephrotoxicity characterized by tubular atrophy, interstitial fibrosis, and arteriolar degeneration (16,17). The chronic pattern is found predominantly in the kidney inner and outer medulla (18), where hypertonicity normally prevails. It is characterized by cell apoptosis (19) and is enhanced by a low-salt diet (20), a circumstance in which the concentrating mechanism is activated, leading to higher medullary tonicity (21). Combined, these observations suggest a maladaptive response to hypertonicity in the presence of CsA. Although CsA was initially thought to target T lymphocytes, it appears to exert a multitude of effects on other cells (22). CsA is retained in the kidney, where tissue levels may reach 10- to 15-fold higher concentrations than blood levels (23). Thus, the predominance of toxic effects in the kidney in CsA-treated patients and animals may relate to the high levels of CsA attained in this organ (23). CsA inhibits calcineurin, a Ca+-calmodulin–dependent phosphatase, which plays a regulatory role in the translocation of several transcription factors to the nucleus. Recent studies suggest that the adaptation of cells to hypertonicity involves various signaling cascades, which may require nuclear translocation of one or more transcription factors (8,9,13,24).
In this study, we show that CsA prevents the nuclear translocation of NFAT5 (TonEBP-OREBP) and inhibits the expression of ORE-mediated luciferase expression in transiently transfected cells. In addition, the expression of BGT1 and HSP70 mRNA is decreased in CsA-treated and hypertonically stressed MDCK (Madin Darby canine kidney) cells. Similarly, the induction of AR, BGT1, and HSP70 mRNA in the medulla of CsA-treated rats is attenuated. We further observed that CsA inhibits proliferation in cultured MDCK cells under isotonic conditions and aggravates hypertonicity-induced apoptosis. In animal studies, histologic examination of the kidneys of CsA-treated rats shows a marked increase in apoptosis in the renal medulla where hypertonicity normally prevails. Our data are consistent with calcineurin-mediated induction of hypertonic stress-response genes. CsA nephrotoxicity may in part result from inhibition of the adaptive responses to hypertonicity, which occurs during the urinary concentrating mechanism.
|
Materials Methods |
|---|
|
TopAbstractIntroductionMaterials MethodsResultsDiscussionReferences |
|---|
Cell Culture and Transfections
Human hepatoblastoma cells (HepG2; American Type Culture Collection [ATCC], Rockville, MD) were grown in Dulbecco modified Eagle medium low-glucose medium (Life Technologies BRL, Rockville, MD) supplemented with 10% fetal calf serum, 2 mM glutamine, and 1% penicillin-streptomycin. Cells (0.25 x 106) within passages 30 to 40 were seeded into 24-well plates (16-mm well diameter) and grown for 24 h. The cells were transfected with 2 µg DNA/well of the various ORE-containing pGL3 constructs. To control for transfection efficiency, cells were cotransfected with pRLTK plasmid (0.2 µg DNA/well; Promega), which expresses the renilla luciferase, and dual luciferase assay was performed. Transfections were carried out via the calcium phosphate precipitation method. The cells were shocked after 6 h with 15% glycerol and allowed to recover for 24 h in isotonic media (315 mosmol/kg H2O). Cells were then exposed to isotonic or hypertonic media (brought to 515 mosmol/kg H2O by the addition of NaCl) for 16 h in the presence of various concentrations of CsA (Calbiochem, San Diego, CA). Cells were harvested, and dual luciferase assay was performed as described previously (8).
MDCK cells (ATCC), within passages 63 to 68, were grown to confluence in isotonic (315 mosmol/kg H2O), serum-free, defined medium (25). Hypertonic conditions were generated by the addition of NaCl or raffinose to isotonic (315 mosmol/kg H2O), inositol- and choline-depleted basic media, bringing the final osmolality to 515 mosmol/kg H2O. Cells were exposed to hypertonic media for 16 h in the presence of various concentrations of CsA (Calbiochem; dissolved in ethanol), rapamycin (Calbiochem; dissolved in DMSO), or the corresponding solvent. All cultures were maintained in 5% CO2/95% air at 37°C.
Northern Blot Hybridization
Total RNA was isolated with RNAzol (Tel-Test Inc., Friendswood, TX). Poly A+ RNA was purified with oligo(dT) columns (Life Technologies BRL), as described previously (26). Equal amounts of RNA per lane were loaded onto 1% agarose–2.2 M formaldehyde gel. The gel was electrophoresed and transferred to GeenScreen membrane (New England Nuclear, Boston, MA). Human AR (27), human HSP70 (ATCC), canine BGT1 (28), and human glyceraldehyde-3-phosphate dehydrogenase (GAPDH; a gift from Dr. W. Zhang, M. D. Anderson Cancer Research Center, Houston, TX) cDNA were labeled with [-32P]dexoycytosine triphosphate (Random Primed DNA Labeling Kit, Boehringer Mannheim, Indianapolis, IN) for use as probes. Probes were hybridized to the blots as described previously (8). Relative band intensities were normalized to GAPDH.
Kinase Assays
The cells were exposed to hypertonic conditions as described above in the presence or absence of CsA, scraped into the experimental medium, and harvested by centrifugation. Cells were lysed in Triton lysis buffer (20 mM Tris, pH 7.4, 137 mM NaCl, 2 mM ethylenediaminetetraacetate, 1% Triton X-100, 25 mM ß-glycerophosphate, 1 mM Na orthovanadate, 2 mM Na pyrophosphate, 10% glycerol, 1 mM phenylmethylsulfonylfluoride, 1 µg/ml leupeptin), and the activities of extracellular regulated kinases (ERK) ERK1 and ERK2, as well as p38 ( and ß) and Jun N-terminal kinase-1 (JNK1), were determined as previously described (8).
Sodium Dodecyl Sulfate–Polyacrylamide Gel Electrophoresis
The sodium dodecyl sulfate–polyacrylamide gel electrophoresis method we used is based on that of Laemmli (29), with slight modifications. Briefly, equal amounts of protein were run on 12% nonreducing gels. Proteins were transferred overnight (4°C, 40 V) onto Hybond-ECL membrane (Amersham, Arlington Heights, IL) in Laemmli buffer (25 mM Tris, 52 mM glycine, pH 8.3), containing 10% methanol. Blots were then blocked for 1 h at room temperature (RT) in PBST (50 mM NaPO4, pH 7.5, 100 mM NaCl, 0.05% Tween-20) containing 5% dried milk. This was followed by a 1-h incubation at RT with monoclonal anti-HSP70 antibody (Stress Gen, Victoria, BC) diluted (1:500) in PBST containing 5% milk. After a 15-min wash in PBST, blots were incubated for 1 h at RT with peroxidase-conjugated secondary antibody diluted (1:500) in PBST containing 5% milk. Blots were then washed for 15 min in PBST, and protein bands were visualized via the ECL-Plus detection system (Amersham Life Sciences, Little Chalfont, Buckinghamshire, England) as per the manufacturer’s instructions.
Cell Proliferation
Rats received intraperitoneal injections of 5-bromo-2'-deoxyuridine (brdU; 10 ml/kg of stock solution; Zymed Laboratories, Inc., South San Francisco, CA) 2 h before tissue harvest. Animals were killed by lethal injection of pentobarbital, and kidney sections (2 to 3 mm) were fixed in buffered formaldehyde (2% formaldehyde, 0.22 M mercuric chloride, 0.1 M sodium acetate; Poly Scientific, Bay Shore, NY) and embedded in paraffin. Detection of brdU incorporation was carried out with biotinylated monoclonal anti-brdU and streptavidin-peroxidase (Zymed). Cultured MDCK cells were incubated for 1 h in brdU (1:100 dilution of stock solution in experimental media). The cells were then scraped and harvested by centrifugation. Cell suspension (107/ml) was spread onto poly-L-lysine–coated slides, dried, fixed in 70% ethanol, washed in phosphate-buffered saline (PBS), and immunolabeled for brdU as above.
Cell Apoptosis
Cultured cell suspension was prepared as described for brdU labeling and was subjected to end-labeling protocol used for kidney tissue. In situ end labeling of fragmented DNA was carried out as described previously (30). Briefly, 3-mm tissue sections were fixed in 2% paraformaldehyde and embedded in paraffin. Three-micron sections were incubated with biotinylated–deoxyuridine triphospate (dUTP) (Boehringer Mannheim) in terminal deoxynucleotidyl transferase buffer (30 mM Tris, pH 7.2, 140 mM sodium cacodylate, 1 mM cobalt chloride). The tissue was then washed in termination buffer (0.3 M NaCl, 0.03 M sodium citrate) and blocked in 2% bovine serum albumin in PBS. After incubation with avidin-peroxidase complex (Vector Laboratories, Burlingame, CA), UTP incorporation was visualized with diaminobenzidine-H2O2. Negative controls were incubated in terminal deoxynucleotidyl transferase buffer without deoxyuridine. Positive controls were treated with DNase for 10 min at RT (1 µg/ml of DNase; Sigma Chemical Co., St. Louis, MO) in buffer containing 30 mM Tris, pH 7.2, 140 mM sodium cacodylate, and 4 mM MgCl2].
NFAT5 Detection
MDCK cells were exposed to isotonic or hypertonic media containing 0 or 5 µg/ml CsA for 16 h. Cells were washed once with PBS and fixed in ice-cold formaldehyde (10% formaldehyde in PBS) for 10 min. Cells were then permeabilized by incubation in Tris-buffered saline (50 mM Tris, pH 8.0, 150 mM NaCl) containing 0.1% Triton X-100 for 5 min at RT. After two washes in PBS, cells were scraped and harvested by centrifugation. Cytocentrifuge smears were prepared from the cell suspensions. Immunostaining was performed via the avidin-biotin-peroxidase complex technique as per the manufacturer’s instructions (Vector Laboratories). Briefly, after blocking with 1% normal goat serum, smears were stained for 1 h at RT with a polyclonal rabbit anti-NFAT5 antibody (TonEBP (31); kindly provided by Dr. Moo Kwon, Johns Hopkins School of Medicine) at a dilution of 1:50 and 1:100. Smears were then incubated with secondary polyclonal goat anti-rabbit antibody at 1:50 dilution for 1 h at RT, followed by incubation with avidin-biotin-peroxidase solution (Vector Laboratories) and chromogen development with diaminobenzidine (1%) and counterstain with 2% methyl green. Negative control included omission of the primary antibody.
Experimental Animals
Male Sprague-Dawley rats (200 g initial weight; Harlan Bioproducts for Science Inc., Indianapolis, IN) were fed rat chow and allowed free access to tap water. Test animals received daily intraperitoneal injections of CsA (25 mg/kg in peanut oil) or rapamycin (Wyeth Laboratories, Philadelphia PA; 1 mg/kg, given by gastric gavage), whereas control animals received vehicle via injections or gavage, respectively. At the end of the experimental period, the animals were killed by lethal injection of pentobarbital. A urine sample was obtained for osmolality determination by direct aspiration from the bladder. After removal of the kidneys from the dead animals, the cortex and medulla were removed and stored at -70°C.
Statistical Analyses
Where indicated, data are presented as means ± SEM. For some of the experiments (indicated in the figure captions), paired or unpaired t test was used for comparison between two groups. All results are considered significant at P < 0.05.
|
Results |
|---|
|
TopAbstractIntroductionMaterials MethodsResultsDiscussionReferences |
|---|
Figure 1A shows that the expression of the 1.5-kb AR promoter–driven luciferase reporter construct in hypertonically stressed HepG2 cells is inhibited by CsA in a dose-dependent manner, whereas the baseline responses in isotonic media are not affected. CsA also inhibited the 132-bp ORE-mediated increase in SV40-driven reporter gene expression in HepG2 cells in a similar dose-dependent manner, thus localizing the effect of CsA to the ORE regulatory enhancer.
|
CsA Inhibits Induction of Stress and Osmoregulatory Genes in Cultured Cells
CsA inhibition of hypertonic induction of stress proteins (heat shock proteins) and genes involved in volume regulation was directly demonstrated in cultured MDCK cells. Heat shock proteins are regulated at the transcriptional level (35), and the abundance of HSP70 mRNA in MDCK cells correlates with that of the protein (Figure 2). Upon exposure to hypertonicity, these cells upregulate the expression of HSP70, BGT1, SMIT, and taurine transporter, but they lack discernible expression of AR gene. Exposure of MDCK cells to hypertonic media for 16 h induces 6- and 10-fold increases in HSP70 and BGT1 mRNA, respectively, compared with cells incubated in isotonic media. The induction of both mRNA is markedly inhibited by CsA at 5 µg/ml concentration (Figure 3A) with complete inhibition at 25 µg/ml (data not shown).
|
|
CsA Augments Hypertonicity-Induced Apoptosis in Cultured Cells
Because CsA nephrotoxicity is characterized by cell apoptosis (19), and because hypertonicity induces cell cycle arrest in cultured cells (37), we examined the effects of hypertonicity on proliferation and apoptosis in cultured MDCK cells and the effect of CsA on these processes. Treatment of cells with either hypertonicity or CsA alone inhibits cell proliferation to the same extent. Apoptosis, on the other hand, is not induced by CsA alone and is only mildly increased by hypertonicity. However, apoptosis is markedly increased by combined exposure of the cells to hypertonicity and CsA (Figure 4). These data suggest that CsA inhibits certain compensatory stress mechanisms in renal cells, thus resulting in cellular injury.
|
|
CsA Induces Apoptosis in the Kidney Medulla
In the following set of experiments, we investigated the effects of long-term CsA treatment, given to rats at a dosage of 25 mg/kg per day for 28 d, on cell proliferation and apoptosis. Long-term treatment of Sprague-Dawley rats with CsA was shown to result in regions of striped fibrosis in the cortex and medulla (39), which are characteristic of chronic CsA nephrotoxicity in humans (16,17). We used immunostaining for brdU to assess cell proliferation and in situ end labeling of fragmented DNA (with biotinylated-dUTP) to detect apoptosis. Notably, although apoptotic cells were observed throughout the kidney, they were most prevalent in the hypertonic renal medulla, which manifested an 18-fold increase in cell apoptosis and a slight increase (1.7-fold) in cell proliferation (Figure 6, 1).
|
|
Cross Talk between JNK1 and a CsA Target
Our findings suggest think that inhibition of osmoprotective genes by CsA is mediated by ORE. We have recently shown that ORE-mediated gene expression in hypertonically stressed cells is dependent on mitogen-activated extracellular regulated kinase kinase and p38 kinase (8,24). To determine whether the effects of CsA were mediated by mitogen-activated protein kinase, we examined the activities of various mitogen-activated protein kinases in hypertonically stressed and CsA-treated MDCK cells. CsA does not affect the activities of ERK1 and ERK2, or of p38 kinase and ß (Figure 7). However, CsA increases JNK1 activity under isotonic conditions, an effect that is magnified by hypertonicity. The observed increase in JNK1 in CsA-treated cells is similar to the previously reported increase in JNK1 after p38 kinase inhibition using SB203580 (24). Because p38 kinase activity was not affected by CsA treatment, the data suggest a cross talk between JNK1 and a shared p38 kinase–CsA target. We conclude that inhibition of osmoprotective genes by CsA is not mediated by downregulation of p38 kinase pathway. Recent data suggest the involvement of JNK1 pathway in ultraviolet light–, 
irradiation–, and ischemia-induced apoptosis (41,42). Hence, the activation of JNK1 in CsA-treated cells may partially explain the observed increase in apoptosis.
|
|
Discussion |
|---|
|
TopAbstractIntroductionMaterials MethodsResultsDiscussionReferences |
|---|
CsA is known to inhibit calcineurin, a protein phosphatase, which mediates the translocation of some NFAT family members to the nucleus (34). Thus, inhibition of ORE-mediated gene expression by CsA may result from an arrest in the translocation of NFAT5 to the nucleus. Because NFAT5 was reported to reside constitutively in the nucleus by one group of investigators (14), whereas two other groups reported its translocation to the nucleus after osmotic stress (9,13), it is likely that NFAT5 regulation may be cell specific (e.g., kidney cells) or stimulus specific (e.g., hypertonicity). Alternatively, CsA may interfere with the activity of factors required for NFAT5 activation or translocation to the nucleus. Interestingly, a recent report suggested that calcineurin may be activated directly by HSP70 (43). Because HSP70 protein is downregulated in CsA-treated cells, a component of calcineurin inhibition may be related to downregulation of HSP70 protein.
It is of particular interest that inhibition of inositol uptake by a specific inhibitor of inositol transporter (SMIT) leads to necrotic medullary injury within 2 d (38). This finding is intriguing because renal cells accumulate a larger quantity of available organic solutes to compensate for the deficiency in others (44). However, the medullary injury reported by Kitamura et al. (38) can be overcome when betaine is given as a substitute organic solute for inositol. On the basis of our data, we think that medullary necrosis does not develop after 5 d of CsA treatment in spite of significant decline in the abundance of AR and BGT1 mRNA. Because no residual inositol transport activity is expected with the metabolic inhibitor, whereas downregulation of the mRNA in our experiments is not complete, we speculate that residual gene products may be sufficient to maintain adequate organic osmolytes levels, at least initially. As a result, the renal injury after CsA treatment may be cumulative and thus assume a chronic nature.
CsA-induced apoptosis has been reported in renal cells in vivo as well as in vitro (19,45–47). Investigation of apoptosis in experimental animals treated with CsA reveals activation of apoptosis-promoting molecules and downregulation of apoptosis-inhibiting molecules, such as bcl-2 (45). In addition, activation of the nitric oxide system (46), transforming growth factor beta (48), and precipitation of tissue ischemia (19) have been suggested to play a role in CsA-mediated renal injury. However, the signaling mechanisms leading to these changes and the overall contribution of each mediator to CsA nephrotoxicity remain to be determined. Our data suggest that inhibition of osmoprotective genes may contribute to CsA nephrotoxicity; downregulation of osmoprotective genes in hypertonically stressed MDCK cells parallels the development of apoptosis. Similarly, downregulation of osmoprotective genes in the medulla of CsA-treated animals precedes the development of apoptosis. Thus, the same mechanism may be responsible for tubular cell death in CsA-treated animals, leading eventually to tissue injury and fibrosis. Most of the apoptotic cells in CsA-treated animals were tubular in origin, whereas most of the proliferating cells were nontubular (located outside of the tubular basement membrane), and morphologically, they appeared inflammatory or fibroblastic in origin, suggesting tubular cell susceptibility to the injurious effects of CsA.
Last, our data, and those reported by Lally et al. (47), suggest that CsA inhibits cell proliferation in tissue culture under isotonic conditions. Similarly, proliferation of cells in the isotonic cortex of CsA-treated animals or humans may be inhibited as well. Thus, cells in the renal cortex may have decreased reserves to sustain or respond to toxic or ischemic injury. Therefore, in the renal cortex, CsA may aggravate renal injury that is sustained by other stresses or cytokines, an effect that may account for some of the cortical changes seen after CsA treatment.
In summary, our findings suggest the involvement of calcineurin in the regulation of stress response genes and offer a plausible mechanism for CsA nephrotoxicity. CsA inhibits two major adaptive responses that facilitate the survival of kidney cells under hypertonic conditions: the induction of osmoprotective genes that lead to the accumulation of organic osmolytes; and heat shock proteins that protect macromolecules from the acute harmful effects of hypertonicity. These CsA effects are particularly important because they attenuate the renal adaptive responses to hypertonicity in vivo. In addition, CsA causes significant alterations in the cell cycle—namely, inhibition of cell proliferation under isotonic conditions and induction of apoptosis under hypertonic conditions. This general mechanism may have a hitherto unappreciated role in the development of other toxic effects of CsA, such as neurotoxicity (49).
|
Acknowledgments |
|---|
|
References |
|---|
|
TopAbstractIntroductionMaterials MethodsResultsDiscussionReferences |
|---|
rgensen KA, Faber V, Flachs H: Ketoconazole and cyclosporine A: Combined effect on rat renal function and on serum and tissue cyclosporine A concentration. Clin Nephrol 25 [Suppl 1]: S137–S143, 1986
-aminobutyric acid transporter (BGT1) gene by hypertonicity. J Am Soc Nephrol 8: 54A, 1997
This article has been cited by other articles:
 |
|
 |
|
  M. B. Burg, J. D. Ferraris, and N. I. Dmitrieva Cellular Response to Hyperosmotic Stresses Physiol Rev, October 1, 2007; 87(4): 1441 - 1474. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 S.-Z. Li, B. W. McDill, P. A. Kovach, L. Ding, W. Y. Go, S. N. Ho, and F. Chen Calcineurin-NFATc signaling pathway regulates AQP2 expression in response to calcium signals and osmotic stress Am J Physiol Cell Physiol, May 1, 2007; 292(5): C1606 - C1616. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
U. Hasler Interplay between TonEBP and calcineurin-NFATc signaling pathways: a means of optimizing water reabsorption? Focus on "Calcineurin-NFATc signaling pathway regulates AQP2 expression in response to calcium signals and osmotic stress" Am J Physiol Cell Physiol, May 1, 2007; 292(5): C1581 - C1582. [Full Text] [PDF]
|
|
|
|
 |
|
 S. W. Lim, K. O. Ahn, M. R. Sheen, U. S. Jeon, J. Kim, C. W. Yang, and H. M. Kwon Downregulation of Renal Sodium Transporters and Tonicity-Responsive Enhancer Binding Protein by Long-Term Treatment with Cyclosporin A J. Am. Soc. Nephrol., February 1, 2007; 18(2): 421 - 429. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 E. H. Y. Tong, J.-J. Guo, A.-L. Huang, H. Liu, C.-D. Hu, S. S. M. Chung, and B. C. B. Ko Regulation of Nucleocytoplasmic Trafficking of Transcription Factor OREBP/TonEBP/NFAT5 J. Biol. Chem., August 18, 2006; 281(33): 23870 - 23879. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. Y. Yang, W. Y. Tam, S. Tam, H. Guo, X. Wu, G. Li, J. F. L. Chau, J. D. Klein, S. K. Chung, J. M. Sands, et al. Genetic restoration of aldose reductase to the collecting tubules restores maturation of the urine concentrating mechanism Am J Physiol Renal Physiol, July 1, 2006; 291(1): F186 - F195. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
G. W. Moeckel, L. Zhang, X. Chen, M. Rossini, R. Zent, and A. Pozzi Role of integrin {alpha}1{beta}1 in the regulation of renal medullary osmolyte concentration Am J Physiol Renal Physiol, January 1, 2006; 290(1): F223 - F231. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
Z. Zhang, J. D. Ferraris, C. E. Irarrazabal, N. I. Dmitrieva, J.-H. Park, and M. B. Burg Ataxia telangiectasia-mutated, a DNA damage-inducible kinase, contributes to high NaCl-induced nuclear localization of transcription factor TonEBP/OREBP Am J Physiol Renal Physiol, September 1, 2005; 289(3): F506 - F511. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. K. M. Lam, B. C. B. Ko, S. Tam, R. Morris, J. Y. Yang, S. K. Chung, and S. S. M. Chung Osmotic Response Element-binding Protein (OREBP) Is an Essential Regulator of the Urine Concentrating Mechanism J. Biol. Chem., November 12, 2004; 279(46): 48048 - 48054. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S.-W. Lim, C. Li, B.-K. Sun, K.-H. Han, W.-Y. Kim, Y.-W. Oh, J.-U. Lee, P. F. Kador, M. A. Knepper, J. M. Sands, et al. Long-term treatment with cyclosporine decreases aquaporins and urea transporters in the rat kidney Am J Physiol Renal Physiol, July 1, 2004; 287(1): F139 - F151. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 Q. Cai, N. I. Dmitrieva, L. F. Michea, G. Rocha, D. Ferguson, and M. B. Burg Toxicity of Acetaminophen, Salicylic Acid, and Caffeine for First-Passage Rat Renal Inner Medullary Collecting Duct Cells J. Pharmacol. Exp. Ther., July 1, 2003; 306(1): 35 - 42. [Abstract] [Full Text] [PDF]
|
|
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
