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Introduction
Diabetic nephropathy (DN) is the leading cause of
end-stage renal disease (ESRD), accounting for 35% of all new
cases in Western countries. Yet the pathogenesis of DN has
not been completely understood. Protein kinase C (PKC) is
known to be involved in the pathogenesis of DN since it
mediates the cellular effects of hyperglycemia, the major
trigger of renal impairment of diabetes mellitus
(DM)[1]. However, the PKC molecule is not uniformitarian; instead, it consists
of 12 subunits with distinct cofactor activation, expression
patterns, and cell functions. Their contribution to the
pathogenesis of DN is not completely clear. PKC-α,
βI, βII, δ, and z have been reported to be activated by high-glucose
concentration in various cell culture models and in the
kidneys of diabetic rats[2,3]. Kang
et al reported that PKC-α was markedly increased in renal glomeruli and interstitial
capillaries as well as in the endothelial cells of large arteries in
strepto-zotocin (STZ)-induced diabetic rats while other isoforms were
less distinctly affected[4].
Recently, Thallas-Bonke et al showed that
PKC-α was especially stimulated by advanced glycation end products in the diabetic
kidney[5]. These data indicate the prominent role
PKC-α in DN. More recently, PKC-α knockout mice were established and their renal
phenotypes were partly investigated by us and other
groups[6,7]. To further elucidate the role of
PKC-α in the pathophysiology of DN with this knockout-mouse model, we investigated
the expression and distribution of PKC-α, which proved to
be different between normal mice and rats, in the kidneys of
diabetic mice.
Both transforming growth
factor-β1 (TGF-β1) and
vascular endothelial growth factor (VEGF) have been implicated in
the pathophysiology of DN. TGF-β1 is involved in
the development of mesangial matrix deposition, glomerular basement
membrane (GBM) thickening, and promoting podocyte apoptosis or detachment in
DN[8_10], whereas VEGF takes part
in the regulation of glomerular permeability, glomerular
endothelial cell growth, and urinary albumin
excretion[11_13]. The enhanced expressions of
TGF-β1 and VEGF stimulated by high glucose have proven to be regulated via a
PKC-dependent pathway[14_16]. A recent study showed that
PKC-α lead to an increased expression of
TGF-β1[17], but other studies have reported that
PKC-α is only involved in the regulation of VEGF and its receptor rather than
TGF-β1 under high glucose
conditions[18]. Therefore, the relations of
PKC-α to TGF β1 and VEGF need further clarification.
It has been demonstrated that angiotensin (Ang) II is
involved in almost every pathophysiological process
implicated in the development of DN, including hemodynamic
changes, hypertrophy, extracellular matrix accumulation,
growth factor/cytokine induction, reactive oxygen
species (ROS) formation, podocyte damage, proteinuria, and
interstitial inflammation[19]. Experimental and clinical studies have
established that blocking the rennin Ang system (RAS)
reduces the glomerular filtration of proteins and delays the
deterioration of renal function in
DN[20,21]. However, the molecule events that underlie the impact of RAS remain unclear.
PKC has been suggested to mediate the effects of RAS. For
example, Ang II was suggested to stimulate the transport of
Na+ in proximal tubules mediated by PKC activation.
Considering that PKC-α gene knockout DN mice exhibited low
urinary protein excretion[6], we assume that blocking RAS
might influence the expression and/or activation of
PKC-α in the kidneys of diabetic mice, which could contribute to
their renoprotective effects.
Materials and methods
STZ, Cy3 conjugated goat anti-rabbit
IgG, rabbit anti-mouse TGF-β1, and VEGF
antibodies were purchased from Sigma (St Louis, MO, USA). Proteinase K,
donkey anti-rabbit IgG conjugated with fluorescein isothiocyanate (FITC)
and donkey anti-goat IgG conjugated with Texas Red were
purchased from San-Ying Co (Wuhan, China).
FITC-conjugated phalloidin was purchased from Alexis Co (San Diego,
CA , USA). Rabbit anti goat PKC-α and, goat anti mouse
Tamm-Horsfall, and aquaporin (AQP)-2 antibodies were
purchased from Santa Cruz Co (San Diego CA, USA). A protein
ELISA kit was purchased from Roche Co (Karlsruhe, Germany). Ang II receptor blocker (ARB) telmisartan was
kindly provided by Boehringer Ingelheim Pharmaceuticals
Inc Co (Shanghai, China). Major apparatus included the
cryosection machine (Leica CM3050S, Nussloch Germany)
and confocal laser-scanning microscopy (Olympus FV500,
Tokyo, Japan).
Animals C57BL/6 male mice (25_35 g) were purchased
from Laboratary of Transplantation Center of Tongji
Hospital(Wuhan, China). All of the experiments were in accordance
with the Regulations for the Administration of Affairs
Concerning Experimental Animals. The diabetic mice were
induced by an intraperitoneal injection of STZ (100 mg/kg
body weight dissolved in cold citrate buffer, pH 4.0) every
other day. One week later, the glucose concentration was
determined in tail blood samples, and only the mice with
blood glucose above 16.7 mmol/L were considered diabetic.
The non-diabetic mice initially injected with STZ vehicle
served as controls (group N, n=6). The diabetic mice then
received telmisartan (9
mg·kg-1·d-1
po, group T, n=7) or
vehicle (group DN, n=7) by gastric tube. During the whole
experiment, the mice had free access to standard mouse chow
and tap water. Two mice, each from the DN and T groups,
died on d 21 and 26, respectively, after the last
administration of STZ. On d 41, 24 h urine samples were collected in
metabolic cages. The protein concentration in the urine was
determined by Coomassie blue G binding assay for protein
with bovine serum albumin as standard. Forty-two days
after the application of STZ or vehicle, the following
experiments were performed on the surviving mice.
Preparation of kidney samples The experimental mice
were anesthetized by intraperitoneal injection of
pentobarbital sodium (70 mg/kg). After opening the abdominal cavity,
the left renal artery was clamped and the left kidney was
excised. The cortex and the outer and inner medulla were
dissected and immediately immersed into liquid nitrogen for
Western blot analysis; then the heart was exposed. The tip
of the perfusion system was inserted into the left ventricle,
and the arterial system was perfused for 1 min with 3_5 mL
PBS (120 mmol/L NaCl, 16 mmol/L
Na2HPO4, and 2.9 mmol/L
KH2PO4) to clear the blood of the kidney, and subsequently
for 10 min with 10_15 mL fixation solution (4%
paraformaldehyde and 3% sucrose in phosphate buffer). Both solutions
were at room temperature. Then the right kidney was
removed and weighed for immunohistochemical and
morphological examinations.
Preparation of cryosections The kidneys were
cut into slices (3 mm thickness) displaying the cortex and
outer and inner medulla. Parts of kidney tissues were fixed with 10%
neutral formalin, imbedded with paraffin, cut into slices
(2 mm thickness), and mounted onto gelatin-coated, glass
slides. The remaining tissues were incubated for 15 min in
the fixation solution at 4 °C. After rinsing in PBS for 15 min,
the kidney slices were dehydrated in 30% sucrose in PBS for
6 h at 4 °C. Thereafter, the kidney slices were frozen in
isopen-tane, precooled by liquid nitrogen and stored at -80 °C until
further use. Cryosections of ~8 µm were made at -20 °C and
transferred onto gelatin-coated, glass slides.
Hematoxylin and eosin (HE) staining and glomeruli
morphometry The sections were deparaffinized with xylene,
rehydrated in graded ethanol, and then stained with periodic
acid-schiff (PAS). Three cryosections of each kidney were
randomly chosen and stained with HE. Thirty glomeruli were
randomly selected from the sections of each subject at an
original magnification of ×400. The following parameters
were determined from light microscopic images using the
HMIAS-2000 system (Qian-Ping Co, Wuhan, China): the
total cell number of glomeruli, mean glomeruli area,
and perimeter.
Immunohistochemistry Immunofluorescence staining
and confocal laser scanning microscopy were performed as
previously described[21]. All steps were performed at room
temperature. Briefly, after pre-incubation
for 20 min in PBS containing 4% normal goat serum or
normal donkey serum plus 1% bovine serum albumin and 0.25% Triton
X-100, the cryosections were incubated for 1.5 h with rabbit anti goat
PKC-α, TGF-β1, and VEGF antibodies (1 µg/mL). For the
negative control, the primary antibodies were pre-absorbed
with their corresponding peptides by incubating them with a
10-fold excess of peptide antigen in PBS for 2 h at room
temperature before the incubation of the sections with the
antibody-peptide solution. After the sections were washed 3
times for 5 min in PBS, they were incubated for 1.5 h with
donkey anti-rabbit IgG conjugated with Cy3 (final
concentration 5 µg/mL; Sigma, USA). The sections were then
washed twice for 10 min in PBS and mounted in FluorSave
(Calbiochem, San Diego, CA, USA) as a fading retardant.
The glomerular fluorescence intensity was determined by
Image-Pro Plus version 5.0 System (Media Cybernetics Inc,
Georgia , USA).
Double-staining experiments were performed with
PKC-α antibodies and a primary antibody against the
respective tissue epitope. For the labeling of filamentous actin in the
foot process of podocytes and proximal tubular brush border,
FITC-conjugated phalloidin (200 U/mL) was used. The
thick ascending limb of Henle's loop was labeled by a polyclonal
antibody (goat antiserum) against the Tamm-Horsfall
protein (2 µg/mL, ICN, Eschwege, Germany). To
study the
expression of PKC in the cortical and
medullary-collecting duct, a polyclonal antibody against AQP-2 (2.0 µg/mL)
was applied. The following secondary antibodies (5µg/mL) were
used: donkey anti-rabbit IgG conjugated with FITC or goat
anti-rabbit IgG conjugated with Cy3 for PKC antibodies,
and donkey anti-goat IgG conjugated with Texas Red for the
anti-AQP2 antibody and for the antibody against the
Tamm-Horsfall protein. The sections were studied by
confocal laser-scanning microscopy.
Western blot analysis Western blot analysis was as
described previously[7]. The total cellular proteins of the
cortex and the outer and inner medulla were obtained
separately by pulverizing the tissue and dissolving the powder in
lysis buffer. Homogenization was followed by
centrifugation (1.000×g, 10 min at 4 °C). The protein content was
determined by the Bradford method, using bovine serum albumin
as standard. Samples were diluted 1:3 with Roti-Load sample
buffer and boiled for 10 min at 65 °C. The following steps
were performed at room temperature: samples of 10 µg
protein were subjected to SDS gel electrophoresis using 10%
acrylamide gels in a Mini-PROTEAN II Electrophoresis Cell
(Bio-Rad Co, München, Germany). For the determination of
molecular weight, a prestained protein ladder was used.
After gel electrophoresis (60 mA/gel, 70 min), the proteins
were transferred to the polyvinylidene-fluoride (PVDF)
membrane of 0.45 µm pore size. The membranes were blocked for
90 min with blocking buffer and rinsed twice with
triethanolamine-buffered saline (TBS) containing 0.1% Tween 20
(TBST). Thereafter, the PKC-α antibodies (0.5 µg/mL) were
incubated overnight in TBST. The secondary horseradish
peroxidase-conjugated antibody was incubated at a
concentration of 0.1 µg/mL for 2 h, RT in TBST. The blots were
rinsed twice with TBST and washed 3 times for 15 min with
TBST, then 2 times in assay buffer at RT. Immunoreactive
proteins were detected using enhanced chemiluminescene
(ECL)-Western blotting detection system according to the
manufacturer's instructions. The membranes were exposed
to Hyperfilm-ECL autoradiography films (Amersham biosciences, Buckinghamshire, UK) for 2 min and quantified
with the image-analysis system MGIAS-1000 (Bio-Rad Co,
München, Germany).
Statistical analysis Data are presented as mean±SEM.
Statistical analysis was carried out by means of one-way
ANOVA using SPSS 10.0 (SPSS Inc Chicago, USA). Pearson's correlation analysis was used to demonstrate
correlations between the data. For all analyses, values ofP<0.05 were considered statistically significant.
Results
General characterization of STZ-induced diabetic mice
More than 16.7 mmol/L blood glucose persisted in
STZ-induced diabetic mice during the 6 week study period, which
could not be attenuated by telmisartan treatment. Body
weight, right kidney weight, right kidney-to-body weight
ratio, and 24 h urinary protein excretion of STZ-induced
diabetic mice were significantly higher than the controls
(P<0.05); these changes could be attenuated by telmisartan
treatment (P<0.05 vs normal and DN mice) (Table 1).
HE staining and morphometric analysis
HE staining revealed a significant increase in mean glomeruli area,
perimeter, and total cell number in the kidneys of STZ-
induced diabetic mice compared to the controls
(P<0.05). These pathological changes could partly be inhibited by
telmisartan treatment (P<0.05 vs normal and DN mice)
(Figure 1).
Immunohistochemistry The distributions of
PKC-α in the kidney of normal, diabetic, and telmisartan-treated
diabetic mice are depicted in Table 2 and illustrated in part in
Figures 2 and 3. In normal mice, immunostaining for
PKC-α was detected in the podocyte of glomeruli, the epithelial cells
of proximal tubules, and medullary-collecting duct (MCD).
There was no significant signal detectable in the medullary
and cortical thick ascending limb (data not shown). The
expression in other glomeruli structures, such as the
mesangial cell-like structure, could not be excluded. The
diabetic mice exhibited similar renal distribution of
PKC-α except for the translocation from the basement membrane to
the apical membrane of epithelial cells in proximal tubules
and from the apical membrane to the basement membrane of
epithelial cells in the inner medullary-collecting duct (IMCD).
Telmisartan treatment could attenuate these changes.
In addition, the enhanced glomerular expressions of
PKC-α, TGF-β1, and VEGF were detected by semiquantitative
immunostaining analysis, and the application of telmisartan
appeared to ameliorate these changes (P<0.05
vs normal and DN groups) (Figure 4). Pearson's correlation analysis
showed a positive correlation of PKC-α to VEGF
(r=0.600, P=0.039), but no correlation to
TGF-β1 (r=0.432, P=0.054).
Western blot analysis The expressions of
PKC-α in the cortex and outer and inner medulla of the kidneys were
determined separately. The PKC-α antibody recognizes 80
kDa bands. Western blot analysis detected an enhanced
expression of PKC-α in the renal cortex and outer medulla of
diabetic mice (P<0.05 vs normal group), while in the
telmisartan-treated diabetic mice, such enhanced expression
was decreased significantly (P<0.05
vs normal and DN groups) (Figure 5).
Discussion
STZ-induced diabetic mice persisted with high blood
glucose until the whole experiment was finished. Similar to
clinical DN, these diabetic mice had higher body weight,
right kidney weight, right kidney-to-body weight ratio, and
24 h urinary protein excretion than the normal control. HE
staining further verified that the pathology changes of these
mice models were in accordance with those of the clinical
DN stage. With confocal laser scanning microscopy, we
found the expression of PKC-α in glomeruli, epithelial cells
of proximal tubules, and MCD of DN mice, but not in the
medullary and cortical thick ascending limb. Such a
distribution of PKC-α is similar to normal mice, but different from
normal rats in the thick ascending limb as reported by Redling
et al[22,23].
However, in epithelial cells of proximal tubules of DN
mice, PKC-α was mostly translocated from the basement
membrane to the apical membrane, which is considered to be
an important sign of PKC-α activation[24], whereas PKC-α was largely translocated from the apical membrane to the
basement membrane in epithelial cells of IMCD, which
denotes decreased activation of PKC-α. These important
findings indicate the different states of activation of
PKC-α may occur in different renal tissues under the same DN
condition. In fact, we also observed in the study that the
expression of PKC-α increased in the renal cortex and outer
medulla, but not in the inner medulla of DN mice.
Undoubted-ly, such different states of activation, as well as expression,
should imply different roles and mechanisms of regulation
of PKC-α in different structures of the kidneys in DN mice.
The observation of enhanced activation of PKC-α in
renal proximal tubules of DN mice in vivo is in accordance
with the in vitro report by Karim et
al[25]. Some investigators
have demonstrated that PKC-α activation is critical for the
inhibition of Na+-K+-ATPase
in epithelial cells of proximal tubules
in vitro[26,27], which is believed to contribute to the
pathogenesis of DM and its
complications[28]. In addition, PKC-α activation was also suggested to be involved in
albumin uptake in proximal tubules in
vitro[29]. Therefore,
enhanced activation of TGF-β1 in renal proximal tubules may
have been associated with function changes in renal
proximal tubules of DN mice. On the other hand, we found, for the
first time, decreased activation of PKC-α in IMCD in DN
mice. So far, few studies have reported the activity of
PKC-α in IMCD, thus little is known about its implication.
Nevertheless, our recent study demonstrates that
PKC-α-deficient mice exhibit impaired urinary concentrating
function due to the defect in IMCD[7]. So such decreased
activation of PKC-α in IMCD is supposed to be responsible for
defective urine concentrating function in DN mice. However,
the mechanisms as to how PKC-α contributes to urinary
concentration under DN conditions, especially the signaling
pathway of its activation or inactivation and its targets, still
needs to be investigated.
Most previous reports focused on the activation of PKC.
In contrast, we observed increased expression of
PKC-α in renal glomeruli, which supports a previous report on the
expression of PKC-α, which mainly affected the kidneys of
diabetic rats[4]. Kang et al suggested that the enhanced
expression of PKC might underlie the sustained PKC
activation observed in diabetes and
hyperglycemia[4]. However, little evidence is available to support such a hypothesis so
far. Recently, the links between PKC-α and TGF-β1 or VEGF
have been proposed. In accordance, we found that the
expressions of TGF-β1 and VEGF were all increased as well
as PKC-α. Moreover, the increased expression of
PKC-α only correlated to VEGF rather than TGF-β1, which was in
accordance with a recent study where PKC-α-deficient mice
were observed[6]. Therefore, despite the lack of direct
evidence, we postulate that the enhanced expression of
PKC-α in renal glomeruli may be involved in the
pathogenesis of DN, at least in association with the increased
expression of VEGF.
It is well known that most of the intrarenal effects of Ang
II are mediated by Ang II type 1 receptor (AT-1R) , which can
be inhibited by ARB producing renoprotective effects, while
the beneficial effects of ARB on the diabetic renal structural
and functional changes in turn provide the evidence for the
role of molecules involved in DN. Recently, the cardiac RAS
was reported to promote PKC translocation in the diabetic
heart via AT-1R, indicating the role of AT-1R in connecting
RAS to PKC, but which PKC isozyme is involved was not
shown[30]. In the present study, we found proteinuria and
right kidney-to-body weight ratio were significantly
ameliorated after the treatment of DN mice with ARB telmisartan.
Meanwhile, the enhanced expression of PKC-α as well as
VEGF in renal glomeruli was attenuated. The different
translocations of PKC-α in renal proximal tubules and IMCD were
also significantly reduced after treatment with telmisartan.
These data not only indicate that the nephroprotective
effects of ARB telmisartan may be mediated more or less by
PKC-α, but also suggest that PKC-α may play a role in the
RAS-PKC signaling cascade in DN.
Taken together, we mainly found the enhanced expression
of PKC-α in renal glomeruli, increased activation of
PKC-α in renal proximal tubules, and for the first time, decreased
activation of PKC-α in IMCD of DN mice. Combined these with
the effects of ARB telmisartan, our findings suggest that
PKC-α may play a role in the pathogenesis of DN, and that
nephroprotective effects of ARB telmisartan may be partly
associated with its influence on PKC-α.
References
1 Brownlee M. Biochemistry and molecular cell biology of
diabetic complications. Nature 2001; 414: 813_20.
2 Haller H. Postprandial glucose and vascular disease. Diabet Med
1997; 14: S50_6.
3 Meier M, King GL. Protein kinase C activation and its
pharmacological inhibition in vascular disease. Vasc Med 2000; 5:
173_85.
4 Kang N, Alexander G, Park JK, Maasch C, Buchwalow I, Luft FC,
et al. Differential expression of protein kinase C isoforms in
streptozotocin-induced diabetic rats. Kidney Int 1999; 56:
1737_50.
5 Thallas-Bonke V, Lindschau C, Rizkalla B, Bach LA, Boner G,
Meier M, et al. Attenuation of extracellular matrix
accumulation in diabetic nephropathy by the advanced glycation end
product cross-link breaker ALT-711 via a protein kinase
C-alpha-dependent pathway. Diabetes 2004; 53: 2921_30.
6 Menne J, Park JK, Boehne M, Elger M, Lindschau C, Kirsch T,et al. Diminished loss of proteoglycans and lack of albuminuria
in protein kinase C-α-deficient diabetic mice. Diabetes 2004;
53: 2101_9.
7 Yao L, Huang DY, Pfaff IL, Nie X, Leitges M, Vallon V.
Evidence for a role of protein kinase C alpha in urine concentration.
Am J Physiol Renal Physiol 2004; 287: F299_304.
8 Chen S, Hong SW, Iglesias-de la Cruz MC, Isono M, Casaretto A,
Ziyadeh FN. The key role of the transforming growth
factor-β system in the pathogenesis of diabetic nephropathy. Ren Fail
2001; 23: 471_81.
9 Wolf G, Chen S,
Ziyadeh FN. From the periphery of the
glomerular capillary wall toward the center of disease: podocyte injury
comes of age in diabetic nephropathy. Diabetes 2005; 54:
1626_34.
10 Chen S, Jim B, Ziyadeh FN. Diabetic nephropathy and
transforming growth factor-beta: transforming our view of
glomerulosclerosis and fibrosis build-up. Semin Nephrol 2003; 23:
532_43.
11 De Vriese AS, Tilton RG, Elger M, Stephan CC, Kriz W, Lameire
NH. Antibodies against vascular endothelial growth factor
improve early renal dysfunction in experimental diabetes. J Am
Soc Nephrol 2001; 12: 993_1000.
12 Flyvbjerg A, Dagnaes-Hansen F, De Vriese AS, Schrijvers BF,
Tilton RG, Rasch R. Amelioration of long-term renal changes in
obese type 2 diabetic mice by a neutralizing vascular endothelial
growth factor antibody. Diabetes 2002; 51: 3090_4.
13 Schrijvers BF, Flyvbjerg A, De Vriese AS. The role of vascular
endothelial growth factor (VEGF) in renal pathophysiology.
Kidney Int 2004; 65: 2003_17.
14 Cha DR, Kim NH, Yoon JW, Jo SK, Cho WY, Kim HK,
et al. Role of vascular endothelial growth factor in diabetic nephropathy.
Kidney Int Suppl 2000; 77: S104_12.
15 Williams B, Gallacher B, Patel H, Orme C. Glucose-induced
protein kinase C activation regulates vascular permeability
factor mRNA expression and peptide production by human vascular
smooth muscle cells in vitro. Diabetes 1997; 46: 1497_503.
16 Hoshi S, Nomoto K, Kuromitsu J, Tomari S, Nagata M. High
glucose induced VEGF expression via PKC and ERK in
glomerular podocytes. Biochem Biophys Res Commun 2002; 290:
177_84.
17 Lindschau C, Quass P, Menne J, Guler F, Fiebeler A, Leitges M,
et al. Glucose-induced TGF-β1 and TGF-β receptor-1 expression
in vascular smooth muscle cells is mediated by protein kinase
C-α. Hypertension 2003; 42: 335_41.
18 Niimi Y, Mochida S, Matsui A, Inao M, Fujiwara K. PKC- and
MAPK-independent upregulation of VEGF receptor expressions
in human umbilical venous endothelial cells following VEGF
stimulation. Hepatol Res 2001; 21: 261_7.
19 Wolf G. New insights into the pathophysiology of diabetic
nephropathy: from haemodynamics to molecular pathology. Eur
J Clin Invest 2004; 34: 785_96.
20 Makino H, Haneda M, Babazono T, Moriya T, Ito S, Iwamoto Y,
et al. The telmisartan renoprotective study from incipient
nephropathy to overt nephropathy-rationale, study design, treatment
plan and baseline characteristics of the incipient to overt:
angiotensin II receptor blocker, telmisartan, Investigation on Type 2
Diabetic Nephropathy (INNOVATION) Study. J Int Med Res
2005; 33: 677_86.
21 Wienen W, Richard S, Champeroux P, Audeval-Gerard C.
Comparative antihypertensive and renoprotective effects of
telmisartan and lisinopril after long-term treatment in hypertensive diabetic
rats. J Renin Angiotensin Aldosterone Syst 2001; 2: 31_6.
22 Redling S, Pfaff IL, Leitges M, Vallon V. Immunolocalization of
protein kinase C isoenzymes α, βI, βII, δ, and z in mouse kidney.
Am J Physiol Renal Physiol 2004; 287: 289_98.
23 Pfaff IL, Wagner HJ, Vallon V. Immunolocalization of protein
kinase C isoenzymes α, βI and βII in rat kidney. J Am Soc
Nephrol 1999; 10: 1861_73.
24 Nishizuka Y. Intracellular signaling by hydrolysis of
phospholipids and activation of protein kinase C. Science 1992; 258:
607_14.
25 Karim Z, Defontaine N, Paillard M, Poggioli J. Protein kinase C
isoforms in rat kidney proximal tubule: acute effect of
angiotensin II. Am J Physiol Cell Physiol 1995; 269: 134_40.
26 Khundmiri SJ, Dean WL, McLeish KR, Lederer ED. Parathyroid
hormone-mediated regulation of
Na+-K+-ATPase requires ERK-dependent translocation of protein kinase Calpha. J Biol Chem
2005; 280: 8705_13.
27 Liang M, Knox FG. Nitric oxide activates PKC-alpha and
inhibits Na+-K+-ATPase in opossum kidney cells. Am J Physiol 1999;
277: F859_65.
28 Bagrov YY, Manusova NB, Egorova IA, Fedorova OV, Bagrov
AY. Endogenous digitalis-like ligands and Na/K-ATPase
inhibition in experimental diabetes mellitus. Front Biosci 2005; 10:
2257_62.
29 Hryciw DH, Pollock CA, Poronnik P. PKC-alpha-mediated
remodeling of the actin cytoskeleton is involved in constitutive
albumin uptake by proximal tubule cells. Am J Physiol Renal
Physiol 2005; 288: F1227_35.
30 Malhotra A, Kang BP, Cheung S, Opawumi D, Meggs LG.
Angiotensin II promotes glucose-induced activation of cardiac protein
kinase C isozymes and phosphorylation of troponin I. Diabetes
2001; 50: 1918_26. |
