Background Image
Table of Contents Table of Contents
Previous Page  8 / 80 Next Page
Information
Show Menu
Previous Page 8 / 80 Next Page
Page Background

CARDIOVASCULAR JOURNAL OF AFRICA • Volume 28, No 3, May/June 2017

142

AFRICA

or function of renal dopaminergic receptors, however the

mechanism is not clear.

11

The exact role of oxidative stress in the

development of HT via NOS inhibition and the regulatory effect

of the anti-oxidant system in this process remains unresolved.

Resveratrol (3,4

,5-trihydroxy-trans-stilbene) (RSV) is a type

of natural phenol found in red grapes, peanuts, red wine and other

polyphenol-rich food. Anti-proliferative,

3,4

anti-inflammatory,

5

anti-oxidant

5-7,12-14

and cardioprotective

15

effects of resveratrol

have been shown in different experimental models so far.

Human studies established that acute administration of

RSV generated dose-dependent improvement of endothelium-

dependent vasodilatation.

16

Aminopiridin-sensitive potassium

channels play a role in that process and a potassium-independent

pathway (propably related to voltage-dependent calcium

channels) is also thought to be responsible for the vasodilatory

efects of RSV.

17,18

Furthermore, it was shown that aortic

vasodilation, with a low dose of RSV, was generated via the

endothelial NOS effect.

19

In our study, we aimed to investigate the effect of resveratrol

on blood pressure in rats that become hypertensive via NOS

inhibition with the application of L-NNA in doses that cause

mild hypertension.

20

Changes in parameters related to water–salt

balance and renal functions were also analysed.

Methods

Male Sprague-Dawley rats (230–260 g) from Harlan were housed

under standard conditions with a 12-hour light–dark cycle in

standard cages in a room with a controlled humidity of 40% and

a temperature of 22°C. They had

ad libitum

access to food and

water for 10 days.

Experimental procedures were in agreement with institutional

and legislator regulations and approved by the local ethics

committee for animal experimentation.

The rats (

n

=

35) were randomly divided into five groups (

n

=

7 in each group): control [intraperitoneal (i.p.) 1 ml 0.9% serum

physiological solution applied for 10 days], L-NNA (15 mg/100

ml L-NNA given with drinking water for 10 days), RSV-E [1 ml

resveratrol eluent (20% ethanol) i.p. applied for 10 days], RSV50

(50 mg/kg resveratrol i.p. applied for 10 days) and L-NNA

+

RSV50 (15 mg/100 ml L-NNA given with drinking water and 50

mg/kg resveratrol i.p. applied for 10 days).

The amount of consumed water was quantified every day and

all applications were performed at the same time of day. The dose

of L-NNA was calculated from the amount of consumed water

and the drinking water of all groups was refreshed every day.

Each subject was placed in a separate box in a quiet area. A

tail-cuff pletysmograph (MAY BPHR 9610-PC TAIL-CUFF

Indirect Blood Pressure Recorder, Ankara, Turkey) and its

sensor were fixed to their tails, which were warmed up to

37–38°C for 10–20 minutes, until it picked up regular signals

and obtained pulses. Systolic blood pressure and heart rate were

measured with the indirect tail-cuff method on the first, seventh

and 10th days of the study by investigators who were blinded

to the study protocol. An average of three measurements was

recorded on each occasion.

All rats were put into metabolic cages at the end of study

protocol. The total water intake and urine output were

determined for 24 hours. We added 0.1 ml 6N HCl to the urine

containers and kept the samples in the dark. Urine samples were

put into Eppendorf tubes and stored at –80°C (Sanyo Ultra Low

Temperature Freezer MDF-U4086S).

At the end of the experiment, the animals were anesthetised

with 20% urethane (1 g/kg, i.p.). Blood samples were collected

by heart puncture, and serum samples were obtained after

centrifugation of the blood at 5 400 rpm for 10 minutes and

stored at –80°C. We measured urea, creatinine and sodium

levels in the blood and urine samples with a Roche Cobas 6000

autoanalyser (Mannheim, Germany).

Fluid balance, sodium clearance rate (C

Na

), glomerular

filtration rate (GFR) and fractional sodium excretion (%FE

Na

)

were calculated using the following formulae:

Fluid balance

=

water intake – urine volume

UFR (urine flow rate in min)

=

​ 

24-hour urine volume

_______________

1 440 

C

Na

=

​ 

urine sodium × UFR

_______________ 

plasma sodium 

GFR

=

​ 

(urine creatinine × plasma creatinine)

__________________________ 

UFR 

%FE

Na

=

​ 

(plasma creatinine × urine sodium)

_________________________  

(plasma sodium × urine creatinine) × 100

Statistical analysis

All statistical analyses were performed with IBM SPSS Statistics

16 software (SPSS Inc, Chicago, IL, USA). Data are expressed as

mean

±

standard error. Blood pressure values were compared with

the Student’s

t

-test and biochemical values via one-way analysis

of varience (ANOVA) with

post hoc

Bonferroni comparison.

All

p

-values were two-tailed and

p

<

0.05 was considered to be

statistically significant.

Results

The body weight gains of all groups were similar and are shown

in Table 1. The first measured blood pressure values (before the

protocol) were similar between the groups (Table 2, Fig. 1). At

the end of the study protocol, blood pressures were higher in the

L-NNA (117.8

±

3.5 vs 149.5

±

2.1 mmHg;

p

<

0.05) and L-NNA

+

RSV50 (122.8

±

7.3 vs 155.4

±

4.4 mmHg;

p

<

0.05) groups

(Table 2, Fig. 1).

Table 1.Weight gain in the study groups

Groups (

n

=

7)

First day (g)

Last day (g)

Control

154

±

5.5

199.4

±

7.2

L-NNA

155

±

3.3

209.0

±

3.3

RSV50

151

±

2.8

188.5

±

4.2

RSV-E

188

±

5.6

214.8

±

16.9

L-NNA

+

RSV50

186

±

6.3

194.3

±

5.2

Table 2. Blood pressure measurements of the study groups

at the beginning and end of the study

Groups (

n

=

7) First measured (mmHg) Last measured (mmHg)

Control

123.1

±

5.5

121.1

±

3.5

L-NNA

117.8

±

3.5

149.5

±

2.1*

βγ

RSV50

122.4

±

3.8

124.2

±

2.4

RSV-E

126.6

±

6.4

121.7

±

7.8

L-NNA

+

RSV50

122.8

±

7.3

155.4

±

4.4*

βγ

*

Compared to the control group,

p

<

0.05;

β

compared to the RSV50

group,

p

<

0.05;

γ

compared to the RSV-E group,

p

<

0.05.