Nephrology and Hypertension Services, Hadassah University Hospital, Jerusalem 91120, Israel
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ABSTRACT |
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The
present study evaluated renal Na+-K+-ATPase
activity and mRNA in rats with diabetes mellitus. To localize the
segmental 1- and
1-mRNAs of
Na+-K+-ATPase 1 and 8 days after induction of
diabetes, we used the polymerase chain reaction after reverse
transcription of the mRNA in microdissected nephron segments.
Na+-K+-ATPase activity in the proximal
convoluted tubule (PCT) rose on days 1 and 8 by
42 and 23%, respectively. In the medullary thick ascending limb
(MTAL), it remained unchanged on day 1 and increased on
day 8 by 55%. In the cortical collecting duct (CCD), activity rose by 81 and 45% on days 1 and 8,
respectively. In parallel,
1-mRNA in the PCT increased
by 52 and 22% on days 1 and 8, respectively. In
the MTAL,
1-mRNA remained unchanged on day 1 and rose by 47% on day 8. In the CCD,
1-mRNA
increased by 140 and 110% on days 1 and 8,
respectively.
1-mRNA was unchanged in the PCT throughout
the study and was elevated in the MTAL and CCD on days 1 and
8. Thus there was a temporal dissociation between
1- and
1-subunit expression. There was a
highly significant linear correlation between
Na+-K+-ATPase activity and
1-mRNA in all nephron segments throughout the
experiment. It appears that microdissection of nephron tubules combined
with reverse transcription-polymerase chain reaction defines the
molecular identity of the amplified gene product and its segmental
distribution in the nephron. We propose that altered gene expression
may be the mechanism underlying enhanced Na+ pump activity
along the nephron in diabetic rats.
diabetes mellitus; streptozotocin; proximal convoluted tubule; medullary thick ascending limb; cortical collecting duct
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INTRODUCTION |
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PREVIOUS STUDIES from this laboratory have demonstrated an increase in renal tubular Na+-K+-ATPase activity in microdissected nephron segments from rats with diabetes mellitus (DM) induced by streptozotocin (STZ) (31, 32). In those studies, we proposed that the increase in Na+-K+-ATPase activity in the proximal convoluted tubule (PCT) and proximal straight tubule was related to augmented cotransport of glucose and Na+ in these segments. In the cortical and medullary thick ascending limbs of Henle's loop (MTAL), the increase in enzyme activity closely followed the rise in glomerular filtration rate (GFR) and, consequently, the augmented delivery of Na+ to the loop of Henle. There was a direct linear correlation between GFR and Na+-K+-ATPase activity in the MTAL. In the cortical collecting duct (CCD), the increase in Na+-K+-ATPase activity was aldosterone dependent. Accordingly, a very close correlation between plasma aldosterone concentration and Na+-K+-ATPase activity in the CCD was evident (32).
The increases in Na+-K+-ATPase activity are consistent with enhanced Na+ absorption in the diabetic kidney. These increases could consist of an increased number and/or enhanced insertion of Na+ pumps in the basolateral membrane.
The transporting enzyme Na+-K+-ATPase consists
of a heterodimer of an -subunit and a
-glycoprotein subunit
(25). The
-subunit is considered to be the catalytic
and transporting subunit, inasmuch as it contains binding sites for
ATP, Na+, K+, and cardiac glycosides (12,
25). Thus the
-subunit is responsible for ATP hydrolysis,
which drives the cation transport. The functional role of the
glycosylated
-subunit is much less defined. It has been suggested
that the
-subunit plays a role in the transfer of the
-subunit
from the
- and
-assembly line in the endoplasmic reticulum, via
the Golgi apparatus, to the cell membrane. Therefore, the
-subunit
appears to exert an accessory and modulatory effect on the active
enzyme (1, 8, 14, 17, 25).
There are three catalytic isoforms of
Na+-K+-ATPase (1,
2, and
3) and two
-isoforms
(
1 and
2), expressed and regulated differentially, depending on the type of tissue (12). In
the rat kidney,
1- and
1-mRNA are
coexpressed at a similar level, which varies along the renal tubule
according to the cell type (6, 7, 10).
The anatomic intricacy of the nephron has made evaluation of site-specific changes in gene expression of Na+-K+-ATPase at the mRNA level difficult. To overcome this difficulty, micromethods have been used by us (21) and others (5) to assess changes in Na+-K+-ATPase activity in response to various pathophysiological conditions.
It has been proposed that the glomerular hyperfiltration in diabetic kidneys may be due to resetting of tubular glomerular feedback (18, 27, 28). This has been attributed to enhanced Na+ reabsorption in the nephron, and it is reflected by increased Na+-K+- ATPase activity. The present study was undertaken to further investigate the mechanism(s) of Na+ hyperabsorption by exploring the changes in Na+-K+-ATPase at the molecular level and at defined tubular segments by means of microdissection.
We employed reverse transcription (RT) and semiquantitative polymerase
chain reaction (PCR) combined with microdissection of individual
nephrons in our experiments. To analyze the distribution of
Na+-K+-ATPase mRNA subunits along the nephron,
we carried out RT-PCR with specific primer pairs for
Na+-K+-ATPase 1- and
1-subunits on microdissected PCT, MTAL, and CCD.
We correlated the alterations of enzyme activity with the gene
expression of 1- and
1-subunits of
Na+-K+-ATPase in isolated nephron segments in
rats 1 and 8 days after induction of DM by administration of STZ.
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MATERIALS AND METHODS |
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Animal experiments were approved by the Institutional Animal Welfare Committee. Male rats of the Hebrew University strain, weighing 200-250 g, were used in all experiments. On day 1, the experimental rats were injected with STZ (55 mg/kg; Sigma, St. Louis, MO) in 0.01 M citrate buffer (pH 7.4), and the control rats received the vehicle only. At 24 h or 8 days after induction of DM, blood was drawn for determination of glucose and aldosterone levels. The rats were killed by dislocation of the neck, the kidneys were removed immediately, and the hilus was cut off and microdissected for Na+-K+-ATPase determination and RNA isolation in the nephron tubules.
To determine the direct effect of high glucose on gene activation, we performed an additional set of experiments. Glucose (50%, 2 ml/100 g body wt) was given by an oral gastric tube to four animals, and blood and urinary glucose levels were measured over a 3-h period at 1-h intervals. By the end of the 3-h measurement period, glucosuria appeared, and the animals were killed and the kidneys were immediately removed and microdissected for Na+-K+-ATPase determination and RNA isolation.
Microdissection
Microdissection of the isolated nephron segments was performed as described by Burg et al. (3) and modified by Schmidt and Horster (22); the procedure was described in detail by Scherzer et al. (21). Briefly, 0.5- to 1.0-mm-thick sagittal slices were cut and immediately immersed in dissection fluid (in mM: 136 NaCl, 3 KCl, 1 K2HPO4, 1.2 MgSO4, 2 CaCl2, 4 sodium lactate, 1 sodium citrate, 6 L-alanine, and 5.5 glucose) plus 0.6% collagenase (145 U/mg; Millipore). The slices were incubated for 30 min in a shaking water bath at 37°C and aerated with 100% O2. The slices were then removed and rinsed twice in ice-cold dissection fluid. Cortical hemicircles, cut at the corticomedullary border, and medullary triangles, including the papilla, were used to obtain the appropriate segments. The slices were transferred to a petri dish with dissection fluid and inserted into a cooled Lucite chamber illuminated by a transmission dark-field source, as described by Schmidt and Horster (22). The length of each segment was measured by an eyepiece micrometer. The segment was rinsed in fresh dissection fluid and transferred to a glass ampule for analysis. The PCT, outer MTAL, and CCD were dissected and used for assay of ATPase activity and isolation of RNA.Determination of ATPase
The method and apparatus for ATPase determination were previously described in detail (21). Briefly, the method is based on the micromodification of the method of Schoner et al. (23), as described by Czaczkes et al. (4). The hydrolysis of ATP was coupled to the transformation of phosphoenolpyruvate to pyruvate by pyruvate kinase. Pyruvate was reduced to lactate in the presence of lactic dehydrogenase. NADH acted as O2 acceptor and was oxidized to NAD+. There was a stoichiometric relationship between the hydrolysis of ATP and the disappearance of NADH (by oxidation to NAD+). This disappearance could be followed fluorometrically.Na+-K+-ATPase was calculated as the difference between total ATPase and Mg2+-ATPase. The latter was determined by addition of ouabain (G-strophanthin) to a final concentration of 4 mM.
Pairs of segments of the same type from the same rat were used for total ATPase and Mg2+-ATPase determinations. Na+-K+-ATPase activity was the mean of the difference of activities measured in these pairs of segments. From each rat, three to five pairs of segments of the same type were dissected. For total ATPase and Mg2+-ATPase activities, 9-16 samples per segment were isolated from 4 or 5 rats. Na+-K+-ATPase activity was compared among the three groups studied: control and 1 and 8 days after STZ administration.
RNA Isolation
Total RNA was extracted from pooled isolated nephron segments (PC, MTAL, and CCD) using a commercially available kit (RNeasy, Qiagen, Chatsworth, CA). After microdissection, the pools of tubules (50-200 mm) were transferred with 5-10 µl of microdissection solution into 400 µl of denaturing solution that contains guanidinium isothiocyanate-containing buffer, which immediately inactivates RNases to ensure isolation of intact RNA. The final RNA pellets were resuspended in 30-60 µl of diethylpyrocarbonate-treated water and quantified by absorbance at 260 nm.cDNA Synthesis and PCR of 1- and
1-Subunits of
Na+-K+-ATPase
The primers for Na+-K+-ATPase subunits were
selected by comparative nucleotide sequence analysis of published cDNA
sequences by Shull et al. (24) for
1-subunits and by Mercer et al. (16) for
1-subunits. For the
1-subunit, the primer
sequence was
5'-CCGGAATTCTGCCTTCCCCTACTCCCTTCTCATC-3' (sense)
and 5'-TGCTCTAGACTTCCCCGCTGTCGTCCCCGTCCAC-3'
(antisense), and the expected size of the PCR product was 331 bp (nt
3207-3529). For the
1-subunit, the primer sequence
was 5'-GTCGAATTCCCTTCCGTCCTAATGACCCCAAGA-3' (sense) and
5'-GCGGGATCCGACCAGAGCAGTTCCCCAGCCAGTC-3'
(antisense), and the expected size of the PCR product was 237 bp (nt
725-943). The primers for the control gene
glyceraldehyde-3-phosphate dehydrogenase (G3PDH) were purchased from
Clontech; the expected length of the PCR product was 930 bp.
PCR
PCR was performed in a thermal cycler (Progene, Techne, Oxford, UK) on 2- to 5-µl aliquots of the first-strand cDNA. The PCR mixture contained 500 ng of each primer, 200 µM of each dNTP, 2.5 U of AmpliTaq polymerase (Promega), and reaction buffer supplied by the manufacturer containing 1.5 mM MgCl2 in a final volume of 25 µl.Amplification was performed as follows: 95°C for 2 min (initial denaturation), 35 cycles at 95°C for 1 min, 55°C for 1 min, and 72°C for 2 min and a final extension at 72°C for 7 min.
Negative controls included dissection medium subjected to RT-PCR, water subjected to PCR, and aliquots from each RNA-containing sample without RT. All negative controls failed to generate PCR products.
cDNA samples derived from three rats (one control, one 1 day after STZ treatment, and one 8 days after STZ treatment) were always amplified simultaneously in the same PCR procedure.
Analysis of PCR Products
After amplification, 10 µl of the PCR products were separated by electrophoresis with a 1.5% agarose gel containing ethidium bromide (0.5 µg/ml; Sigma) in 0.04 M Tris acetate-0.001 M EDTA buffer. Ethidium bromide-stained product bands of expected size were visualized under ultraviolet (UV) light, and the size was confirmed by comparison with synthetic DNA size markers (100-bp DNA ladder; MBI Fermentas, Amherst, NY). Band intensities ofIn each experiment, serial dilutions of cDNAs obtained by RT from
tubules of control animals and from animals 1 and 8 days after STZ
treatment were performed for the control gene G3PDH. The purpose of
these dilutions was to ensure a constant reference quantity of the
control gene. This served to semiquantify the variations in
1- and
1-subunit cDNA vs. control cDNA
after simultaneous amplifications with the corresponding primers for
the same number of cycles. Thus we were dealing with a fixed amount of
the control gene, which served as a standard for comparison, and we
assayed the changes in
1- and
1-subunits
accordingly. The band intensities of
1- and
1-subunits of Na+-K+-ATPase in
the nephron segments were calculated from samples in which signal
intensity of the control gene remained unchanged by UV imaging. The
results were calculated as the ratio of intensities of
1- and
1-subunits to the intensity of the
control gene, which served as the standard. Data are expressed as
percent change in cDNA density of the different experimental groups
compared with the control group, which served as baseline.
Linearity of the Primers
Individual reactions were performed for different numbers of cycles with 500 nmol of G3PDH andNorthern Blot Analysis
Because we used G3PDH as internal control in normal and diabetic rats, we performed Northern blot analysis to determine whether its expression was modified by the diabetic state. Northern blots were performed as previously described (20). Membranes were hybridized to cDNAs of G3PDH or 18S, which served as control.Southern Blot Analysis
To verify the molecular identities of the G3PDH andBlood Sample Analysis
Blood glucose levels were measured using a Glucometer Elite (Bayer, Elkhart, IN). Aldosterone levels were determined by radioimmunoassay (ALDOCTK-125-M, Sorin Biomedica). All reagents were purchased from Sigma.Statistics
Values are means ± SE. Analysis of variance was performed for statistical evaluation between the groups. Results of individual groups were compared by a nonpaired Student's t-test with a modified level of significance according to Bonferroni's method (9). ![]() |
RESULTS |
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Linearity of the Primers in PCR
We have established the linear conditions for the PCR experiments with G3PDH and
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Northern Blot Analysis
The results of Northern blot analysis of G3PDH and 18S, which served as control, are depicted in Fig. 2. DM did not modify G3PDH expression in all nephron segments studied before (control) and 1 and 8 days after induction of DM by STZ administration.
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Blood Glucose in STZ-Treated Rats
Blood glucose levels in control and STZ-treated rats are shown in Table 1. Blood glucose was high after 24 h (P < 0.001 vs. control) and remained high 8 days after induction of DM (P < 0.001 vs. control).
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Aldosterone Levels
Aldosterone levels in control and STZ-treated rats are listed in Table 1. At 1 day after STZ administration, aldosterone levels increased from 29.5 ± 2.5 (control) to 58.2 ± 3.5 ng/100 ml (P < 0.001). After 8 days, aldosterone levels decreased to 45.2 ± 2.5 ng/100 ml but remained above control levels (P < 0.001 vs. control) and were significantly lower than 1 day after STZ administration (P < 0.02 vs. 1 day after STZ).Effects of STZ on Na+-K+-ATPase Gene Expression
PCT.
Typical results of RT-PCR analysis of mRNA expression of
1- and
1-subunits of
Na+-K+-ATPase in isolated PCT from STZ-treated
rats 1 and 8 days after induction of DM are depicted in Fig.
3A. An increase in
1-subunit (331 bp), but not
1-subunit
(237 bp), product density in the PCT of the diabetic kidney is
apparent. Negative controls demonstrated no contamination in the
reaction mixture. Expression of the control gene G3PDH (930 bp)
was unchanged in control and experimental PCTs.
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MTAL.
Changes in expression of 1- and
1-mRNA of
Na+-K+-ATPase are depicted in Fig.
4. In Fig. 4A, a typical
representative gel of RT-PCR products from MTAL RNA in control and
diabetic rats shows no change in expression of the control gene G3PDH.
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CCD.
Figure 5A shows a
representative gel for RT-PCR products of the CCD RNA. An increase in
PCR product density of 1- and
1-subunits in the CCD of diabetic kidneys is apparent 1 and 8 days after STZ.
There was no change in G3PDH levels. The Southern blots with
1- and
1-mRNA-specific oligonucleotide
probes confirmed the identity of Na+-K+-ATPase
1- and
1-subunits (data not shown).
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Relationships Between Na+-K+-ATPase
Activity and 1-Subunit Expression
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Acute Glucose Load
After acute intragastric glucose load, blood glucose levels were 111 ± 5 (baseline), 498 ± 20 (after 1 h), 400 ± 25 (after 2 h), and 329 ± 30 mg/dl (after 3 h; n = 4 each). Urinary glucose was tested with a dipstick and was negative at baseline, became positive after 2 h, and rose further at 3 h (>200 mg/dl). Table 2 shows Na+-K+-ATPase activity and
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DISCUSSION |
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Our present experiments demonstrated that the rise in
Na+-K+-ATPase activity in isolated renal
tubules in rats with STZ-induced DM is associated with an increase in
the abundance of 1-mRNA of the enzyme along the nephron.
The relationship in the nephron segments is illustrated in Fig. 6.
There was a highly significant linear correlation between
Na+-K+-ATPase activity and the level of
1-mRNA in the PCT, MTAL, and CCD. At variance with the
1-mRNA, there was no change in
1-mRNA abundance in the PCT throughout the 8 days of the experimental period.
In the MTAL, an early increase in
1-mRNA was observed 1 day after induction of DM and was maintained until 8 days after induction of DM. Similarly, in the CCD, an increase in
1-mRNA was observed 1 day after STZ induction of DM, and
a further rise was apparent 8 days after induction of DM.
In normal rats, after 3 h of glucose load accompanied by
glycosuria, an impressive increase in
Na+-K+-ATPase activity was observed in the PCT
without changes in gene expression of 1- and
1-subunits (Table 2). This would suggest that, at this
stage,
1- and
1-subunits of the enzyme
were recruited to the cell membrane and that activation of gene
expression by glucose could be ruled out.
Because Na+-K+-ATPase activity generally
reflects the rate of Na+ uptake and its vectorial transport
across the tubular epithelium, it is plausible to suggest that the rate
of Na+ transport may play a role as a major regulator of
1-subunit gene expression. In this regard, it is
appropriate to draw an analogy to experiments in isolated renal
epithelial cells reported by others. In those experiments, the amount
of Na+-K+-ATPase in cell membranes was
modulated according to the demand for transport capacity through the
influence of Na+ concentration in the cytoplasm, which
enhances the transcription rates of
Na+-K+-ATPase (10). In suspensions
of kidney tubule cells, an increase in the cytoplasmic
Na+-to-K+ ratio triggered an early rise in the
amount of specific mRNA of Na+-K+-ATPase
followed by an increase in the rate of synthesis of
1- and
1-subunits (10). Similarly, in our
model of STZ-induced DM in rats, an increased filtered and delivered
load of Na+ to the tubular epithelial cells resulted in
adaptive increases in the abundance of
1-mRNA of
Na+-K+-ATPase and a parallel rise in the enzyme
activity. Only the
1-subunit contains specific binding
sites for Na+, and it is possible that its synthesis could
be influenced by Na+ delivery to the PCT and MTAL.
It is noteworthy that the 1-mRNA of
Na+-K+-ATPase was altered independently of the
enzyme activity. Thus, after 24 h,
Na+-K+-ATPase activity was totally dissociated
from changes in
1-subunit gene expression in the PCT and
MTAL; similarly, the magnitude of alteration after 8 days was
different. Similar to our findings, Ver et al. (29)
demonstrated a dissociation between mRNA levels of
1-
and of
1-subunits in STZ-treated diabetic rats in the kidney and heart 2 and 4 wk after induction of DM. Farman et al. (7) also demonstrated a dissociation between
1- and
1-mRNA after adrenalectomy in
nondiabetic rats. In this experimental setting, adrenalectomy was
followed by a significant decrease in
1-mRNA in the
early distal tubule and in the CCD, whereas
1-mRNA
abundance was unaffected (7).
In the CCD, changes in 1-mRNA abundance correlated
with the enzyme activity. However, in this segment of the nephron,
enzyme activity and gene expression appear to be regulated by
aldosterone levels and are less affected by variations in
Na+ delivery and uptake. Expression of
1-mRNA of Na+-K+-ATPase and the
enzyme activity increased significantly in the CCD 1 day after
induction of DM. At this stage, GFR was not increased (31,
32) and the enzyme activity was unchanged in the MTAL. However,
changes in
1-mRNA in the CCD were seen 1 day after
induction of DM, and they closely paralleled changes in aldosterone
levels. Thus it appears that in the CCD, as opposed to the MTAL,
alterations in
1-mRNA and enzyme activity are induced
primarily by aldosterone levels, while in the MTAL the changes mainly
depend on variations in GFR and the accompanying rise in
Na+ delivery (32). Verrey et al.
(30) demonstrated that aldosterone alters the gene
expression of the
1-subunit in a manner that is
independent of Na+ entry into A6 kidney cells, which bear
some similarity to epithelial cells of the CCD. Similarly, it appears
that the effect of aldosterone on CCD
1-mRNA in diabetic
rats in the present experiments was dissociated from changes in
Na+ uptake in this nephron segment. Using a different
experimental model, Tsuchiya et al. (26) presented similar
results. In their experiments, adrenalectomy selectively decreased
1-mRNA in rat CCD. They concluded that regulation of
Na+-K+-ATPase in the CCD in vivo can be
attributed, at least in part, to mineralocorticoid-dependent control of
Na+-K+- ATPase
1-mRNA abundance.
Furthermore, it has been speculated that aldosterone could have a direct effect on the splicing and stability of mRNA. It is also of interest that, in the CCD, aldosterone in the presence of triiodothyronine increases the amount of Na+-K+-ATPase by de novo synthesis of new pump units independent of changes in cytoplasmic Na+ (2).
Increasing evidence has accumulated suggesting that the
-subunit plays a role in regulating the assembly, oligomerization, and functional maturation of the Na+ pump (1, 8, 14,
17, 25). Because there is an excess of
1-mRNA,
1-subunit mRNA becomes the limiting factor, which is
presumably regulated by mineralocorticoids (8). In our
present experiments in rats with STZ-induced DM, the level of
aldosterone was increased 1 day after induction of DM, and at that time
a substantial increase in
1-mRNA was detected in the
CCD. Thus it is possible that aldosterone played a key role in
enhancing synthesis of
1-subunit mRNA in this nephron
segment. Changes in
1-subunit gene expression did not
exactly follow the variations in aldosterone levels,
Na+-K+-ATPase activity, and
1-subunit gene expression. This discrepancy between
1- and
1-mRNA is not surprising, since
the
1- and
1-subunit genes are located on
different chromosomes (11, 33) and display distinct
tissue-specific expression (19). The regulatory sequences on each gene might be different, which might explain the differential effect of aldosterone on the transcription of
1- and
1-subunit genes.
An increase in 1-mRNA in the MTAL preceded changes in
enzyme activity and
1-mRNA, but 8 days after induction
of DM, enzyme activity and
1- and
1-subunit gene expression displayed a similar increment.
The early increase in
1-subunit gene expression was not
associated with change in Na+-K+-ATPase
activity and, thus, probably was not associated with altered active
Na+ transport. Therefore, it appears that the diabetic
state and, possibly, hyperglycemia could have a direct impact on
1-subunit gene expression in this segment. It is also
suggested that synthesis of the
1-subunit precedes that
of the
1-subunit, which is in agreement with the
findings of McDonough et al. (15).
In summary, our present experiments, based on RT-PCR methodology in
isolated nephron segments, helped delineate alterations in
Na+-K+-ATPase 1- and
1-mRNA in correlation with enzyme activity in experimental DM. The most striking finding of the present study was a
highly significant linear correlation between
Na+-K+-ATPase activity and the abundance of
1-mRNA in diabetic rats. We and others proposed that the
glomerular hyperfiltration may be due to resetting of tubuloglomerular
feedback in the nephrons of the diabetic kidney (18, 27,
28). This has been linked with Na+ hyperabsorption
in the nephron as reflected by enhanced
Na+-K+-ATPase activity. The present study
further explored this phenomenon using methods of molecular biology.
These results suggest that altered gene expression may be the
underlying mechanism for enhanced activity of the Na+ pump
and Na+ absorption along the nephron in STZ-treated
diabetic rats.
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FOOTNOTES |
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Address for reprint requests and other correspondence: P. Scherzer, Nephrology and Hypertension Services, Hadassah University Hospital, POB 12000, Jerusalem 91120, Israel (E-mail: henrietta{at}hadassah.org.il).
The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
10.1152/ajprenal.00053.2001
Received 20 February 2001; accepted in final form 28 September 2001.
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REFERENCES |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
1.
Ackermann, U,
and
Geering K.
Mutual dependence of Na-K-ATPase - and
-subunits for correct posttranslational processing and intracellular transport.
FEBS Lett
269:
105-108,
1990[ISI][Medline].
2.
Barlet, C,
and
Doucet A.
Triiodothyronine enhances renal response to aldosterone in the rabbit collecting tubule.
J Clin Invest
79:
629-631,
1987[ISI][Medline].
3.
Burg, M,
Grantham J,
Abramow M,
and
Orloff J.
Preparation and study of fragments of single rabbit nephrons.
Am J Physiol
210:
1293-1298,
1966[ISI][Medline].
4.
Czaczkes, JW,
Venek GG,
and
Burg MB.
Assay of sodium- and potassium-activated adenosine triphosphatase in submicrogram fragments of renal tubules.
Anal Lett
12:
893-904,
1979[ISI].
5.
Doucet, A,
Katz AI,
and
Morel F.
Determination of Na-K-ATPase activity in single segments of the mammalian nephron.
Am J Physiol Renal Fluid Electrolyte Physiol
237:
F105-F113,
1979[ISI][Medline].
6.
Farman, N.
Na-K-ATPase expression and distribution in the nephron.
Miner Electrolyte Metab
22:
272-278,
1996[ISI][Medline].
7.
Farman, N,
Coutry N,
Logvinenko N,
Blot-Chabaud M,
Bourbouze R,
and
Bonvalet JP.
Adrenalectomy reduces 1 and not
1 Na-K-ATPase mRNA expression in rat distal nephron.
Am J Physiol Cell Physiol
263:
C810-C817,
1992
8.
Geering, K,
Theulaz I,
Verrey F,
Häuptle MT,
and
Rossier BC.
A role for -subunit in the expression of functional Na-K-ATPase in Xenopus oocytes.
Am J Physiol Cell Physiol
257:
C851-C858,
1989
9.
Godfrey, K.
Comparing the means of several groups.
N Engl J Med
313:
1450-1456,
1985[Abstract].
10.
Jørgensen, PL,
Mei Meng L,
and
Pedersen PA.
Structure and regulation of Na-K-ATPase in the kidney.
In: Molecular Nephrology: Kidney Function in Health and Disease, edited by Schlöndroff D,
and Bonventre JW.. New York: Dekker, 1995, p. 349-368.
11.
Kent, RB,
Fallows DA,
Geissler E,
Glaser JR,
Emanuel JR,
Lalley PA,
Levenson R,
and
Houseman DE.
Genes encoding - and
-subunits of Na-K-ATPase are located on three different chromosomes in the mouse.
Proc Natl Acad Sci USA
84:
5369-5373,
1987[Abstract].
12.
Lingrel, JB,
Orlowski J,
Shull MM,
and
Price EM.
Molecular genetics of Na-K-ATPase.
Prog Nucleic Acid Res Mol Biol
38:
37-89,
1990[ISI][Medline].
13.
Manniatis, T,
Fritsch E,
and
Sambrook J.
Molecular Cloning: A Laboratory Manual. Cold Spring Harbor, NY: Cold Spring Harbor Laboratory, 1982.
14.
McDonough, AA,
Geering K,
and
Farley RA.
The sodium pump needs its -subunit.
FASEB J
4:
1598-1605,
1990
15.
McDonough, AA,
Magyar CE,
and
Komatsu S.
Expression of Na-K-ATPase - and
-subunits along rat nephron: isoform specificity and response to hypokalemia.
Am J Physiol Cell Physiol
267:
C901-C908,
1994
16.
Mercer, RW,
Schneider JW,
Savita A,
Emanuel J,
Benz EJ,
and
Levenson R.
Rat brain Na-K-ATPase -chain gene: primary structure, tissue-specific expression and amplification in ouabain-resistant HeLa C+ cells.
Mol Cell Biol
6:
3884-3890,
1986[ISI][Medline].
17.
Noguchi, S,
Mishina M,
Kawamura M,
and
Numa S.
Expression of a functional (Na + K)-ATPase from cloned cDNAs.
FEBS Lett
225:
27-32,
1987[ISI][Medline].
18.
Popovtzer, MM,
Wald H,
and
Scherzer P.
The diabetic kidneylesson in the resetting of tubuloglomerular feedback.
In: Proceedings of the 4th Asian-Pacific Congress of Nephrology, edited by Jinhong Z,
Xuehai D,
Zhihong L,
and Leishi L.. Beijing: International Academic Publishers, 1991, p. 379-382.
19.
Rossier, BC,
Geering K,
and
Kraehenbuhl JP.
Regulation of the sodium pump: how and why.
Trends Biol Sci
12:
483-487,
1987.
20.
Scherzer, P,
Nachliel I,
Ziv E,
Bar-On H,
and
Popovtzer MM.
Effects of variations in food intake on renal sodium pump activity and its gene expression in Psammomys kidney.
Am J Physiol Renal Physiol
279:
F1124-F1131,
2000
21.
Scherzer, P,
Wald H,
and
Czaczkes JW.
Na-K-ATPase in isolated rabbit tubules after unilateral nephrectomy and Na+ loading.
Am J Physiol Renal Fluid Electrolyte Physiol
248:
F565-F573,
1985[ISI][Medline].
22.
Schmidt, U,
and
Horster M.
Na-K-activated ATPase: activity maturation in rabbit nephron segments dissected in vitro.
Am J Physiol Renal Fluid Electrolyte Physiol
233:
F55-F60,
1977[ISI][Medline].
23.
Schoner, W,
Von Ilberg C,
Kramer R,
and
Seubert W.
On the mechanism of Na+- and K+-stimulated hydrolysis of adenosine triphosphatase. 1. Purification and properties of Na+- and K+-activated ATPase from ox brain.
Eur J Biochem
1:
334-343,
1967[ISI][Medline].
24.
Shull, GE,
Greeb J,
and
Lingrel JB.
Molecular cloning of three distinct forms of the NaK-ATPase -subunits from rat brain.
Biochemistry
25:
8125-8132,
1986[ISI][Medline].
25.
Sweadner, KJ.
Isoenzymes of the Na-K-ATPase.
Biochim Biophys Acta
988:
185-220,
1989[ISI][Medline].
26.
Tsuchiya, K,
Giebisch G,
and
Welling PA.
Aldosterone-dependent regulation of Na-K-ATPase subunit mRNA in the rat CCD: competitive PCR analysis.
Am J Physiol Renal Fluid Electrolyte Physiol
271:
F7-F15,
1996
27.
Vallon, V,
Blantz RC,
and
Thomson SC.
Homeostatic efficiency of tubuloglomerular feedback is reduced in established diabetes mellitus in rats.
Am J Physiol Renal Fluid Electrolyte Physiol
269:
F876-F883,
1995
28.
Vallon, V,
Richter K,
Blantz RC,
Thomson S,
and
Osswald H.
Glomerular hyperfiltration in experimental diabetes mellitus. Potential role of tubular reabsorption.
J Am Soc Nephrol
10:
2569-2576,
1999
29.
Ver, A,
Szanto I,
Csermely P,
Kalff K,
Vegh E,
Banyasz T,
Marcsek Z,
Kovacs T,
and
Somogy J.
Effect of streptozotocin-induced diabetes on kidney Na-K-ATPase.
Acta Physiol Hung
83:
323-332,
1995[Medline].
30.
Verrey, F,
Kraehenbuhl JP,
and
Rossier BC.
Aldosterone induces a rapid increase in the rate of Na-K-ATPase gene transcription in cultured kidney cells.
Mol Endocrinol
3:
1369-1376,
1989[Abstract].
31.
Wald, H,
Scherzer P,
and
Popovtzer MM.
Enhanced renal tubular ouabain-sensitive ATPase in streptozotocin diabetes mellitus.
Am J Physiol Renal Fluid Electrolyte Physiol
251:
F164-F170,
1986[ISI][Medline].
32.
Wald, H,
Scherzer P,
Rasch R,
and
Popovtzer MM.
Renal tubular Na,K-ATPase in diabetes mellitus: relation to metabolic abnormality.
Am J Physiol Endocrinol Metab
265:
E96-E101,
1993
33.
Yang-Feng, TL,
Schneider JW,
Lindgren V,
Schull MM,
Benz EJ,
Lingrel JB,
and
Francker U.
Chromosomal localization of human Na-K-ATPase - and
-subunit genes.
Genomics
2:
128-138,
1988[Medline].
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