Key words
nitroglycerine - renal ischemia-reperfusion injury - rat
Introduction
AKI has been defined as a sudden reduction (for a few hours) in kidney function with
structural damage and loss of function [1]. AKI is manifested by a significant increase in serum Cr and reduction of urine
output [2]. The pathophysiology of AKI is divided into tubular and vascular causes. In the
AKI induced by vascular damage, renal medullary blood flow decreases, leading to a
reduction in total renal perfusion. The AKI is associated with damage to the endothelium
of arterioles, characterized by the increased vascular contraction in response to
elevated tissue levels of endothelin I and II, thromboxane A2, and leukotrienes C4
and D4. Moreover, vasodilation decreases in response to acetylcholine, bradykinin,
and nitric oxide [3]. The renal injury initiates from the onset of ischemia and continues after the reperfusion,
the tissues undergo subsequent damage. Generation of cytokine and oxygen free radicals
also neutrophil accumulation occurs in renal ischemia and reperfusion injury. During
Ischemia the tubular cells and their residues are separated from the basement membrane
that reacts with proteins like fibronectin and forms protein casts that causes a tubular
obstruction and, therefore, increased intratubular pressure [4]. In renal ischemia and reperfusion injury, the tubular disruption activates the
tubuloglomerular feedback mechanism that reduces glomerular filtration rate (GFR)
to prevent water and electrolytes loss [5]. The animal ischemia-reperfusion model is used in fundamental and treatment studies
on AKI [6].
Nitric oxide (NO) is an effector molecule and a lipophilic free radical, the physiological
effects of which are exerted by cGMP [7]. NO has a half-life of 6–30 s [8] and in the kidney is produced by three isoforms of NOS: endothelial NOS(eNOS or
NOS3) in renal vessels, neuronal NOS (nNOS or NOS1) in the macula densa, and inducible
NOS (iNOS or NOS2) in renal tubular segments, in the glomerulus, and intertubular
and renal arcuate arteries [9].
The molecular and chemical effects of NO are administered by preventing neutrophil
filtration, reducing the pro-inflammatory cytokines, inhibiting platelet aggregation
and therefore reducing vascular inflammation and improving perfusion to ischemic tissue
[10]
[11]
[12]. The role of NO in the regulation of endothelium vasomotor tone decreases the effect
of vascular contraction and promotes endothelial-dependent vasodilatation, which improves
perfusion to ischemic tissue [8]
[10].
Nitroglycerin (NG) is a potent vasodilator has been used in the treatment of angina
pectoris heart failure and high blood pressure acts through the liberation of nitric
oxide (NO) . NG is an organic nitrate that reacts with thiols and other reducing substrates
[11]. It is converted into 1, 2- glyceryl dinitrate and nitrite in the vascular smooth
muscle cells, which is then metabolized by mitochondrial aldehyde dehydrogenase 2
with a half-life of 1–4 min [13]
[14].
Regarding the NO characteristics and the ability of nitroglycerin to release exogenous
nitric oxide (NO donor) in our present study, we aim to evaluate the effects of treatment
with nitroglycerin after renal ischemic reperfusion injury.
Materials and Methods
This study was conducted on 24 Wistar rats weighing 250–300 g and kept in separate
cages under a photoperiod of 12 h light/12 h dark at room temperature (about 23±2
°C) and with ad libitum access to food and water. All ethical codes created by the
Monitoring Committee for Laboratory Animals of Arak University of Medical Sciences
were complied with for all of the studied rats. The study groups included: (1) the
control group that did not receive any drugs, (2) the sham group that were anesthetized
without any ischemia (the kidneys were only touched), (3) the I-R group that experienced
bilateral ischemia of the renal arteries and veins for 20 min and then reperfusion
for 24 h, and (4) the post-treatment group that were injected with intra peritoneal
(IP) NG (Caspian Tamin, Iran) at 50 μg/kg, 24 h after reperfusion started [15].
To induce AKI, the rats were weighed first and then injected with IP sodium thiopental
(Sandoz, GmbH, Estonia) at 25 μg/kg [16]. After shaving the hair on the back of the rats, 1.5 cm incisions were made on either
side of the midline using scissors and forceps. When the kidneys became visible, a
special clamp was employed to block renal arteries and veins for 20 min., after which
the clamps were removed immediately. The surgery sites were then closed and the animal's recovered.
After recovery, the rats were placed in metabolic cages and the 12-h urine volume
was measured using the gravimetric method. The rats were anesthetized 24 h after reperfusion.
Systolic blood pressure was measured using a Power Lab instrument (AD Instruments,
Australia) [17]
[18] and employing the tail-cuff method. A longitudinal incision was then made on the
surface of the abdomen using a razor blade. When the abdomen was opened, the kidneys
were revealed. The artery and vein of the left kidney were separated and renal blood
flow (RBF) was measured for 30 min using a flow meter equipped with a special probe
(T402, America) and blood flow was recorded as a chart [19]
[20].
A cold blood collection heparin syringe was used to collect blood from the abdominal
aorta. After obtaining the plasma, an Auto Analyzer (Selectra-XL, Netherlands) was
employed to measure plasma [Cr] and [blood urea nitrogen (BUN)] in the serum and blood
samples [21]. A flame photometer (SEAC-20Fp, Italy) was used to measure [Na+] and [K+] and an osmometer (Gonotec Osmomat-030, Germany) to measure osmolality [22]
[23]. Creatinine clearance level and absolute and relative excretions of potassium and
sodium were determined using the following equation [24]:
CCr(μl/min/gkw) = (V°/1000×UCr)/PCr
Absolute sodium excretion UNaV°(μmol/min/gkw) = (V°×UNa)/1000
Absolute excretion of potassium UKV°(μmol/min/gkw) = (V°×UK)/1000
Relative sodium excretion based on percentile FENa = (UNa×PCr)/(PNa×UCr)×100
Relative potassium excretion base on percentile FEK = (Uk×PCr)/(Pk×UCr)×100
Both kidneys were removed and weighing them, they were divided into two halves. The
right kidney was placed in liquid nitrogen for the ferric reducing antioxidant power
(FRAP) and malondialdehyde (MDA) biochemical analyses and then immediately placed
in a freezer at −20°C. The amount of lipid peroxidation was determined by Okawa’s
MDA method. Benzie and Strain’s method was used to measure FRAP [25]
[26].
The capsule of the left kidney was separated and placed in 10% buffered formalin.
It was then fixed, dehydrated, and clarified before being embedded in melted paraffin.
Following that, 5-micron-thick sections were prepared and stained with hematoxylin
and eosin. Examination of tissue from prepared slides was performed by an expert pathologist.
Bowman’s capsule space, reduction in the number of glomerular red blood cells (RBC),
shedding of tubular epithelial cells into the lumen, formation of protein casts inside
the lumen, and vacuolation and necrosis of tubular cells were evaluated. The amount
of inflicted damage was graded based on calculated percentages as follows: no damage:
grade 0, 1–25% damage: grade 1, 25–50% damage: grade 2, 50–75% damage: grade 3 and
75–100% damage: grade 4 [27].
In addition, all data were analyzed with SPSS version 25 (Chicago, Il., USA), one-way
variance (ANOVA), the Tukey test, Kruskal-Wallis multiple comparison test, and Dunnett’s
test at P<0.05 as the significance level for statistical analysis [28].
Result
The effects of post-treatment NG on RBF and systolic blood pressure
In compared to the control group, RBF showed a significant decrease in the NG group
(7.36±0.02 ml/min., P<0.001), in the I-R group (6.42±0.31 ml/min., P<0.001), and in
the sham group (8.5±0.2 ml/min., P<0.01). The NG group showed a significant increase
compared to the I-R group (P<0.01). There were no significant differences between
the groups in systolic blood pressure ([Fig. 1]).
Fig. 1 Comparison of a Renal blood flow and b Systolic blood pressure among the groups. P<0.001*** compared to the control group,
P<0.001+++compared to the sham group, P<0.001□□□ compared to the I-R group, Results
expressed in mean ±standard deviation (SD) for 6 rats in each group.
Post-treatment effects of NG on Creatinine clearance (CCr), absolute (UNaV°) and relative (FENa) excretions of sodium, and absolute (UkV°) and relative (FEk) excretions of potassium
Results indicated that creatinine clearance declined significantly in the I-R group
(0.008±0.005 µl/min. gkw;P<0.001) and in the NG group (0.02±0.006 µl/min.gkw) compared
to the control and sham groups (0.05±0.01 µl/min.gkw). There was a significant increase
of CCr in the NG group (P<0.001).
There was a non-significant increase in the fractional excretion of Na+(FENa) of the I-R group compared to the control group (0.42±0.2% vs. 0.39±0.3%). The FENa in the NG group (0.001±0.0008%) declined significantly compared to the I-R group
at P<0.01 and the control group at P<0.05, but was not significantly different from
that of the sham group. The absolute excretion of Na+(UNaV°) did not differ significantly among the groups. The fractional excretion of potassium
(FEK ) in the I-R group showed a significant increase compared to the control group (47.28±13.3%
vs. 28.6±9.8%, P<0.05). Moreover, the FEK decreased significantly in the NG group (21.73±7.7%) compared to the sham group (47.74±13.8%,
P<0.05) and the I-R group (47.28±13.3%), but had no significant difference with that
of the control group. The absolute excretion of K+(UkV° ) in the I-R group (0.82±0.2 µmol/min.gkw, P<0.001) declined significantly compared
to the control and sham groups (2.68±0.3 and 2.16±0.2 µmol/min.gkw, respectively),
whereas there were no significant differences between the NG and the I-R groups ([Table 1])
Table 1 Comparison of creatinine clearance (CCr), absolute (UNaV°) and relative (FENa) excretions
of sodium and absolute (UkV°) and relative (FEk) excretions of potassium.
|
CCr µl/min.gkw
|
UNaV0 µmol/min.gkw
|
UKV0 µmol/min.gkw
|
FENa %
|
FEK %
|
Parameters Groups
|
|
0.05±0.01
|
0.56±0.1
|
2.68±0.3
|
0.39±0.3
|
28.6±9.8
|
Control
|
|
0.05±0.01
|
0.58±0.1
|
2.16±0.2
|
0.28±0.05
|
42.7±13.8
|
Sham
|
|
0.008±0.005
|
0.47±0.1
|
0.82±0.2
|
0.42±0.2
|
42.7±13.3
|
I/R
|
|
***
|
|
***
|
|
*
|
|
|
+++
|
|
+++
|
|
|
|
|
0.02±0.006
|
0.49±0.1
|
1.33±0.2
|
0.001±0.0008
|
21.7±7.7
|
TNG+I/R
|
|
*
|
|
***
|
*
|
+
|
|
|
▫▫▫
|
|
+
|
▫▫
|
▫▫
|
|
|
+
|
|
|
|
|
|
P<0.001***, P<0.01**, P<0.05* compared to the control group. P<0.001+++, P<0.01++,
P<0.05+compared to the sham group. P<0.001□□□, P<0.01□□, P<0.05□ compared to the I-R group. Results expressed in mean ±standard deviation (SD) for 6 rats in each group.
Post-treatment effects of NG on urinary levels of sodium ([Na]u), potassium ([K]u), creatinine ([Cr]u), and osmolality (Osmolu)
Urinary sodium concentration in the I-R group was significantly higher than the control
group (28.72±8.4 μmol/mL vs. 65.73±6.9 μmol/mL, P<0.001). The urinary concentration
of sodium in the NG group (32.11±5.3 μmol/mL) did not differ significantly from those
in the sham (32.33±3.9 μmol/mL) and control groups. The urinary concentration of sodium
in the NG group declined significantly compared to the I-R group (P<0.001).
Urinary potassium concentration in the I-R group exhibited a significant decrease
compared to the control group (133.63±13.6 μmol/mL vs. 112.9±2.7 μmol/mL, P<0.01).
The urinary concentration of potassium in the NG group (88.76±5.8 μmol/mL) was significantly
lower than those in the sham (120.28±9.13 μmol/mL, P<0.001) and control groups (P<0.001)
and in the I-R group (P<0.01). Although urinary potassium concentration in the I-R
group was lower than that in the sham group, this difference was not significant.
The groups did not exhibit any significant differences in urinary concentration of
creatinine.
Urine osmolality in the I-R group decreased significantly compared to the control
group (908.33±48.12 mOsm/KgH2 O vs. 1515±70.5 mOsm/KgH2O, P<0.001). Urine osmolality in the NG group (1031.5±58.23 mOsm/KgH2O, P<0.001) declined significantly compared to the sham (1493.83±80.85 mOsm/KgH2O) and control groups (P<0.001), but did not differ significantly compared to the
I-R group ([Table 2]).
Table 2 Comparison of urinary concentrations of sodium ([Na]u), potassium ([K]u), creatinine ([Cr]u) and osmolality (Osmolu) among the groups.
|
Osmolu mosm/KgH2O
|
[Cr]u mg/dl
|
[K]u µmol/ml
|
[Na]u µmol/ml
|
Parameters Groups
|
|
1 515±70.5
|
1.38±0.2
|
133.63±13.6
|
28.72±8.4
|
Control
|
|
1 493.83±80.8
|
1.33±0.3
|
120.28±9.1
|
32.33±3.9
|
Sham
|
|
|
|
▫▫▫
|
|
|
908.33±48.1
|
1.25±0.2
|
112.9±2.7
|
65.73±6.9
|
I/R
|
|
***
|
|
**
|
***
|
|
|
+++
|
|
|
|
|
|
1 031.5±58.2
|
1.32±0.2
|
88.76±5.8
|
32.11±5.3
|
TNG+I/R
|
|
***
|
|
***
|
▫▫▫
|
|
|
+++
|
|
+++
|
|
|
|
|
▫▫
|
|
|
P<0.001***, P<0.01**, P<0.05* compared to the control group. P<0.001+++, P<0.01++,
P<0.05+compared to the sham group. P<0.001□□□, P<0.01□□, P<0.05□ compared to the I-R group. Results expressed in mean ±standard deviation (SD) for 6 rats in each group.
Post-treatment effects of NG on plasma concentrations of sodium ([Na]p), potassium ([K]p), creatinine ([Cr]p), urea ([BUN]p), and osmolality (Osmolp)
Results indicated that plasma creatinine concentration in the I-R group(1.24±0.35 mg/dL)
significantly increased (P<0.001) compared to the control group (0.55±0.09 mg/dL)
and the sham group (0.64±0.08 mg/dL), whereas in the NG group plasma creatinine concentration
(0.77±0.13 mg/dL, P<0.01) exhibited a significant reduction compared to the I-R group,
but did not significantly differ from those of the control and sham groups.
Plasma concentration of BUN in the I-R group (41.11±6.5 mg/dL) significantly increased
compared to the control group (18.76±2.4 mg/dL, P<0.001) and the sham group (24.9±3.1 mg/dL,
P<0.01). There were no significant differences between the NG and the I-R groups.
Compared to the control group, plasma concentration of sodium in the I-R group experienced
a decline, which was not significant (149.23±6.2 μmol/ml vs. 152.1±6.1 μmol/mL, P<0.01).
The plasma concentration of sodium in the NG group (141.46±2.6 μmol/mL, P<0.01) decreased
significantly compared to the control group but did not differ significantly from
those of the sham (144.45±6.7 μmol/mL) and I/R groups.
The plasma concentration of potassium and osmolality did not show any significant
differences between groups ([Table 3]).
Table 3 Comparison of plasma concentrations of sodium ([Na]p), potassium ([K]p), creatinine ([Cr]p) and osmolality (Osmolp) among the groups.
|
Osmolp mosm/KgH2O
|
[BUN]p mg/dl
|
[Cr]p mg/dl
|
[K]p µmol/ml
|
[Na]p µmol/ml
|
Parameters Groups
|
|
309.16±30.2
|
18.76±2.4
|
0.55±0.09
|
3.66±0.4
|
152.1±6.1
|
Control
|
|
305.66±6.1
|
24.9±3.1
|
0.64±0.08
|
3.79±0.4
|
144.45±6.7
|
Sham
|
|
318.83±10.06
|
41.11±6.5
|
1.24±0.3
|
4.02±0.5
|
149.23±
|
I/R
|
|
***
|
***
|
|
|
|
|
++
|
+++
|
|
|
|
|
332.16±19.7
|
38.18±4.3
|
0.77±0.1
|
3.91±0.5
|
141.46±2.6
|
TNG+I/R
|
|
***
|
▫▫
|
|
***
|
|
|
+
|
|
|
|
|
P<0.001***, P<0.01**, P<0.05* compared to the control group. P<0.001+++, P<0.01++,
P<0.05+compared to the sham group. P<0.001□□□, P<0.01□□, P<0.05□ compared to the I-R group. Results expressed in mean ±standard deviation (SD) for 6 rats in each group.
Post-treatment effects of NG on MDA and FRAP levels in renal tissue
Results showed that the MDA level per gram kidney weight (gkw) significantly increased
in the I-R group (35.68±6.41 μmol/gkw) compared to the control group (15.33±4.21 μmol/gkw)
and the sham group (20.41±3.3 μmol/gkw) (P<0.001). The MDA levels did not differ significantly
in the sham and control groups. The MDA level in the NG group (24.66±2.4 μmol/gkw)
exhibited a significant increase compared to the control and sham groups (P<0.01)
and a significant reduction compared to the I-R group (P<0.01; [Fig. 2a]).
Fig. 2 Comparison of a MDA and b FRAP levels among the groups. P<0.001*** compared to the control group, P<0.001+++,
P<0.01++compared to the sham group, P<0.001□□□, P<0.01□□ compared to the I-R group,
Results expressed in mean ±standard deviation (SD) for 6 rats in each group.
In the I-R group the kidney tissue level of FRAP (5.69±0.5 mmol/gkw) declined significantly
compared to the control group (8.61±1.06 mmol/gkw) and the sham group (7.59±0.3 mmol/gkw).
The tissue level of FRAP were not significantly different in the control and sham
groups. The FRAP level in the NG group (8.69± 1.4 mmpl/gkw) increased significantly
compared to the I-R group (P<0.001), but did not differ significantly from that of
the control group ([Fig. 2b]).
Post-treatment effects of NG on histological changes (▶Fig. 3)
Results demonstrated that necrosis of tubular cells (grade 3), vacuolation of tubular
cells (grade 2), increased Bowman’s capsule space (grade 1), formation of protein
casts within the tubular lumen (grade 2), scattering of cells into the tubule lumen
(grade 3), reduction in the number of glomerular red blood cells (grade 1), and glomerular
injury (grade 2) in the I-R group were significantly different compared to the control
group (grade 0) (P<0.05). Increased Bowman’s capsule space and cell necrosis in the
sham group (grade 1) were significantly different compared to the control group (P<0.05).
Moreover, necrosis of tubular cells (grade 1), vacuolation of tubular cells (grade
0), formation of protein casts within the tubular lumen (grade 0), scattering of cells
inside the tubular lumen (grade 0), reduction in the number of glomerular red blood
cells (grade 0), and glomerular injury (grade 0) were significantly different compared
to the I-R group (P<0.05), whereas the increase in Bowman’s capsule space (grade 1)
was not significantly different compared to the I-R group ([Fig. 3]
).
Fig. 3 Comparison of renal histological between different groups. a - Control group with glomerular and normal tubular structure(×40); b- I-R group with tubular cell necrosis, formation of protein casts inside the tubule
lumen, cells scattering into the tubule lumen, vacuolation of tubular cells, increased
Bowman’s space and reduced number of red blood cells in glomerulus(×40); c - sham group with tubular cell necrosis(×40); d –Nitroglycerin group with increased Bowman’s space, vacuolation of tubular cells
and reduced tubular cell necrosis(×40). RBC: Red Blood Cell, N: Necrosis, C: Intratubular
cast, D: Downfall, V: Vacuolization, BS: Bowman’s space.
In the NG group, necrosis of tubular cells (grade 2) significantly increased compared
to the control and sham groups (P<0.05), but declined significantly compared to I-R
group (P<0.05). In the NG group, increased Bowman’s capsule space (grade 2), formation
of protein casts (grade 2), vacuolation (grade 2), glomerular injury (grade 2), cell
scattering (grade 2) and reduction in the number of glomerular red blood cells (grade
1) were not significantly different compared to the I-R group ([Table 4]).
Table 4 Comparison of necrosis level, protein casts, cell scattering, vacuolation, the reduced
number of red blood cells, increased Bowman’s capsule space, and glomerular injury.
|
Parametes
|
Cell necrosis
|
Vacuolation
|
Increased Bowman’s capsular space
|
Formation of protein casts
|
Cell scattering
|
Reduced number of red blood cells
|
Glomerular injury
|
|
Groups
|
|
|
|
|
|
|
|
|
Control
|
0
|
0
|
0
|
0
|
0
|
0
|
0
|
|
Sham
|
1
|
0
|
1
|
0
|
0
|
0
|
0
|
|
*
|
▫
|
*
|
▫
|
▫
|
▫
|
▫
|
|
▫
|
|
|
|
|
|
|
|
I/R
|
3
|
2
|
1
|
2
|
2
|
1
|
2
|
|
*
|
*
|
*
|
*
|
*
|
*
|
*
|
|
+
|
+
|
|
+
|
+
|
+
|
+
|
|
TNG+I/R
|
2
|
2
|
2
|
2
|
2
|
1
|
2
|
|
*
|
*
|
*
|
*
|
*
|
*
|
*
|
|
+
|
+
|
+
|
+
|
+
|
+
|
+
|
|
▫
|
|
▫
|
|
|
|
|
P<0.05* compared to the control group. P<0.05+compared to the sham group. P<0.05□ compared to the I-R group. Results expressed in mean ±standard deviation (SD) for
6 rats in each group.
Discussion
The results of the present study indicated that renal ischemia-reperfusion injury
accompanied by increased plasma creatinine and BUN and by reduced creatinine clearance
[29]. These results could be due to back-leak of filtrate and impaired ion re-absorption
that leads to renal tubular obstruction with the decrease in GFR in the reperfusion
stage. Furthermore, sodium is not appropriately re-absorbed by the injured proximal
tubules (which activates tubuloglomerular feedback). This feedback probably participates
in constriction of pre glomerular arteries that further decreases GFR [30]. The creatinine clearance level in the NG group increased significantly compared
to the I-R group. Previous research has shown that NG increases NO and cGMP levels
[31]. Increased intracellular cGMP levels dilate the afferent and efferent arteries,
thus increasing clearance of creatinine [32]. There was a plasma electrolyte disorder in the I-R group compared to the control
group. The FENa in the I-R group increased compared to the control group, but this increase was not
significant. The FEK was also higher in the I-R group. This increase indicates that epithelial tubular
cells, especially proximal tubular cells, are damaged during ischemia-reperfusion
injury [26]. In addition, ischemia-reperfusion injury causes brush border destruction with reduced
re-absorption of sodium by proximal tubules, impaired expression of tubular sodium
transporters, and unsuitable regulation of Na+/K+-ATPase expression in the basal-lateral membranes [23]
[33]. During I-R, damage to the principal cells of the late portion of the distal tubule
and the cortical collecting duct results in direct injury to cells responsible for
K+secretion [34]. The NG decreased urinary sodium secretion compared to the I-R group. These results
can be due to the fact that the effect of NO on tubular sodium transport differs in
the various parts of the nephrons. Results obtained by Wu et al. indicated that during
the direct inhibitory effect of NO on renal proximal tubular Na+transport, the renal sympathetic nervous system stimulated proximal tubular Na+transport during I-R injury. Many studies have been conducted on isolated tubule segments
and not on intact kidneys [35]. Moreover, NG increases plasma renin activity [36]. In cortical collecting ducts (CCD), NO inhibits basolateral potassium conductance
[37]. Urine osmolality in the I-R group significantly declined compared to the control
group due to impaired urinary concentrating ability. Unsuitable regulation of the
AQPs and Na+transporter proteins in renal tubules is responsible for changes in sodium and water
regulation under the influence of ischemia-reperfusion injury [23]. Urine osmolarity in the NG group was not significantly different from that of the
I-R group. This may be due to the effect of NO because it inhibits ADH-sensitive sodium
and water permeability in the principle cells through a cGMP increasing mechanism
[37]
[38]. Ischemia-reperfusion injury significantly increased the MDA levels and significantly
decreased the FRAP levels in the kidney tissues. Previous research demonstrated that
ischemia-reperfusion injury caused an imbalance between ROS sources and the antioxidant
defense system (reduced glutathione peroxidase, catalase, and superoxide dismutase)
[39]. During the reperfusion phase, the produced oxygen free radicals lead to lipid peroxidation
[40]. The NG decreased MDA level compared to the I-R group and increased the FRAP level
compared to the I-R group. Previous studies indicated that treatment with NG increased
plasma catalase and glutathione peroxidase activity while reducing malondialdehyde
levels in rats also NG improved antioxidant properties [41]. In the present study, the groups did not significantly differ in blood pressure
probably due to the intervention of short-and intermediate-term blood pressure control
mechanisms whereas kidneys are long-term blood pressure regulators.
In the present study, Ischemia-reperfusion injury significantly decreased the renal
blood flow rates compared to the sham and control groups probably due to the fact
that increased renal vascular resistance (RVR) could act as a vascular response to
cellular events that happened because of ischemia. Increased RVR may activate vasoactive
factors and ROSs that can influence perfusion. Ischemia-reperfusion injury activated
the sympathetic nervous system, the renin-angiotensin system and also increased generation
of endothelin A , prostaglandins and platelet-activating factors (PAF) among vasoconstrictor
agents effective in reducing RBF [42]. The RBF rates in the sham group decreased significantly compared to the control
group probably due to effects of anesthesia and surgical stress. Research by Mercatello
showed that anesthesia drugs influenced renal function not only directly, but also
through changes in cardiovascular function and endocrine activity. Many barbiturates
tend to decrease RBF [43].The RBF rates in the NG group increased significantly compared to the I-R group.
Previous studies indicated that NG inhibited contraction of vascular smooth muscles
through increasing cGMP and reduced effect of exogenous endothelin-1 on heart and
kidney function. NG also neutralizes increases in EP, NE, and aldosterone caused by
Endothelin [31]. Histological studies in the present research revealed that, contrary to the control
group, necrosis of tubular cells, vacuolation of tubular cells, increased Bowman’s
capsule space, formation of protein casts within the tubular lumen, cell scattering
into the tubular lumen, decreased number of glomerular red blood cells, and glomerular
injury happened in the I-R group. The pathological analysis did not show the improvement
effect in the group that received the drug. Imbalance between expression and activity
of eNOS and iNOS (reduction in eNOS activity and increase in iNOS expression level)
is responsible for the pathology results during I-R injury [9]. Previous research also did not show any improvement in the histological changes
during I-R injury by the NG [44]. The authors believe that the time of using NG also plays a very important role
in pathological changes.
Conclusions
Results of the present study indicated that post-treatment intraperitoneal injection
of Nitroglycerin reduces renal ischemia reperfusion injury. Nitroglycerin improved
the renal tissue antioxidant defense system by increasing level of FRAP and also reducing
lipid peroxidation. Nitroglycerin improved hemodynamic parameters the same as plasma
creatinine, creatinine clearance, and renal blood flow through generation of nitric
oxide (NO).
Further investigation requires determining the protective effect of nitroglycerin
against renal ischemia-reperfusion injury in human kidneys. Additional examinations
need to determine the incidence of renal ischemia-reperfusion injury in nitroglycerin-treated
patients with acute heart failure.
IRB Ethical Approval Number
IRB Ethical Approval Number
The Research Ethics Committee of Arak University of Medical Sciences approved this
research under registration number IR.ARAKMU.REC. 1396.287.
Informed Consent
This was not a research on humans. All ethical codes developed by the Monitoring Committee
for Laboratory Animals at Arak University of Medical Sciences were complied within
the experiments conducted in the present research.
Support sources
Deputy of Education and Research, Arak University of Medical Sciences, Grant number:2858.
