SUPEROXIDE DISMUTASE ACTIVITY (SOD) IN PLACENTAS

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5
SU
P E R O X I D(2002)
E-DISMU
T A S E - A75-80
CTIVITY-(SOD)-IN-PLACENTAS
Zoologica
Poloniae
47/3-4:
75
SUPEROXIDE DISMUTASE ACTIVITY (SOD)
IN PLACENTAS COMPLICATED WITH PREGNANCY
INDUCED HYPERTENSION (PIH)
J OLANTA S ACZKO 1 , M A£GORZATA D ACZEWSKA 2 ,
A NNA M ARCINKOWSKA 1 , A GNIESZKA C HWI£KOWSKA 1 ,
ZBIGNIEW S ACZKO3, A NTONI OGORZA£EK4 AND T ERESA BANAŒ1
Wroc³aw Medical University, Department of Medical Biochemistry,
Cha³ubiñskiego 10, 56-368 Wroc³aw, Poland
2
Laboratory of Evolutionary and Developmental Biology of Vertebrates, Zoological
Institute, University of Wroc³aw, Sienkiewicza 21, 50-335 Wroc³aw, Poland
3
Specialized Hospital, Warszawska 2, 50-335 Wroc³aw, Poland
4
Department of General Zoology, Zoological Institute, University of Wroc³aw,
Sienkiewicza 21, 50-335 Wroc³aw, Poland
1
Abstract. Superoxide dismutase (SOD) activity was investigated in 10 normal
placentas and 15 placentas from women with diagnosed pregnancy induced hypertension
(PIH). We found differences in superoxide dismutase (SOD) activity between pathological and normal placentas. SOD activity in normal pregnancies was maintained at a stable
level, whereas in PIH placentas SOD it was lower compared to normal placentas. Single
cases of SOD activity increase in pathological placentas were observed. The results
concerning SOD confirm the role of oxidative stress in etiopathogenesis of pregnancy
induced hypertension.
INTRODUCTION
Hypertension-associated disorders in pregnant women are a frequent cause
of death, premature births, stillbirths and complications in infants. Etiopathogenesis of most cases of pregnant women hypertension remains unknown.
In chronic hypertension the main feature is enhanced arterial tension,
whereas in pregnancy induced hypertension (PIH) the increased tension is a
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syndrome of specific disorders and potential cause of complications in pregnant women (B ROWN et al., 2000; J OHENNING at al., 1997).
The latest studies suggest involvement of oxidative stress inducing uncontrolled increase of reactive oxygen species (ROS) in the PIH etiopathogenesis (H UBEL et al. 1997, C ANIGGIA at al. 2000). It is presumed that the
focus of pathological alterations is placenta which uses much oxygen for its
activity (M YATT et al., 2000). The first symptoms of pregnancy induced hypertension are observed in the period of normally formed placenta, both structurally and functionally (about 20th week of pregnancy).
In physiological conditions there are specific regulatory mechanisms
maintain the proper ROS level in the cell. Among them an important role is
played by antioxidative enzymes: superoxide dismutase (SOD), catalase (CT),
glutathione reductase (Rx-GSH) and glutathione peroxidase (GPx). SOD converts superoxide O 2 - into H 2 O 2 . CT catalyzes disproportionation reaction of
hydrogen peroxide. GPx accounts for reduction of hydrogen peroxide and organic
peroxides using reduced glutathione, whereas glutathione reductase regenerates reduced form of glutathione at the cost of NADPH (B ARTOSZ , 1995;
T USUKIMORI , 1993; W ANG , 1996). In oxidative stress conditions antioxidative
balance system is disturbed, which could lead to changes in the activity of
these enzymes.
The aim of this study was to compare the SOD activity in normal placentas and placentas complicated with pregnancy induced hypertension (PIH), as
well as to assess the involvement of oxidative stress in etiopathogenesis of
pregnancy induced hypertension.
MATERIAL AND METHODS
The material included 10 normal placentas (pregnancies finished within
the 38th - 40th week) and 15 placentas from women with diagnosed pregnancy
induced hypertension (pregnancies finished within the 35th - 40th week). The
placentas were obtained from the Specialized Hospital of Gynecology and
Obstetrics in Wroclaw, Poland.
Pregnancy induced hypertension was diagnosed when the value of systolic arterial pressure exceeded 140 mm Hg and the mean value of diastolic
pressure was higher than 90 mm Hg. The blood pressure was being measured
after the 20th week of pregnancy. Before pregnancy the women did not suffer
from chronic arterial hypertension and after delivery their blood pressure returned
to normal values without pharmacological treatment.
For the measurements, fragments of the central part of placental discus
(2.5 g) were taken. The samples were immediately frozen at -80°C. To remove
red cells, before homogenization the frozen fragments were cleansed in buffer
consisting of 0.9% NaOH, 0.5 mM PMSF, 0.5 mM EDTA, pH 7.4. Homogenization of the tissue was carried out in 10 mM phosphate buffer, pH 7.4 with
0.5 mM EDTA for 10 minutes. The obtained homogenates were centrifuged at
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SUPEROXIDE-DISMUTASE-ACTIVITY-(SOD)-IN-PLACENTAS
77
750 g for 20 minutes. The total protein content was measured with Bradford's
(1976) method.
SOD activity was determined according to Segura-Aguilar method (1993).
RESULTS
The obtained results showed differences in superoxide dismutase (SOD)
activity between the pathological and normal placentas. SOD activity in normal placentas was maintained at a stable level (about 1.2 nmol H 2 O 2 x 0.1 x
min -1 x mg -1 ), whereas in PIH placentas the SOD activity was lower compared
to normal placentas. Only single cases of SOD activity increase were observed in pathological placentas (Fig. 1).
SOD (nm H 2 O 2 x min -1 x mg -1 )
1.6
1.4
SOD activity
1.2
1
0.8
0.6
0.4
0.2
0
Fig. 1. SOD activity in normal and pathological placentas.
DISCUSSION
Etiopathogenesis of the pregnancy induced hypertension (PIH) has not
been fully elucidated yet. The results of the latest studies indicate that the
focus of the majority of PIH symptoms is placenta (G RATACOS at al., 1999;
M UTLU -T URCOGLU , 1998). Therefore studies on PIH usually concentrate on
placenta and maternal vessels supplying it with blood (R OGGENSACK , 1998).
It has been found that an essential factor affecting occurrence of pregnancy induced hypertension is oxidative stress, associated with increase in
ROS level (H UBEL , 1998; W ANG , 1998; B UHIMSCHI , 2001). During normal preg-
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nancy increased usage of oxygen is observed, which results in increased level
of reactive oxygen species, which in physiological conditions are maintained
at a stable level, not causing pathological changes (13).
There exist many metabolic disorders resulting from oxidative stress during
pregnancy, for example: increase in lipid peroxidation in placenta, as well as
augmentation of -SH groups oxidation in biological membranes (SKOCZYLAS P IETRZYK , 1998; K INALSKI , 1999). These phenomena could also be the consequence of a decreased activity of the antioxidative system enzymes, where
superoxide dismutase (SOD) plays an important role.
In the present studies it was shown that SOD activity clearly decreases
in the PIH placentas in comparison to the normal placentas. It is also true with
respect to other enzymes of the antioxidative system, such as catalase, glutathione peroxidase and glutathione reductase (W IKTOR , 1998; S IKKEMA , 2001).
The present studies showed both decrease and increase in SOD activity in
pathological placentas in comparison to normal placentas.
Uncontrolled increase in ROS level in oxidative stress conditions in the
beginning could stimulate the activity of the examined enzyme, and then might
lead to its activity inhibition (R OGGENSACK , 1999), which is confirmed by this
study. Therefore, it could be assumed that a decrease or increase in SOD
activity in the examined PIH placentas may depend on the degree of pathological changes, their time and the undertaken treatment, which demands a specific clinical monitoring of PIH patients.
The obtained results provide evidence for disturbances in pro-antioxidative
system, whose direct reason could be oxidative stress.
PONADTLENKOWA DYSMUTAZA (SOD) W £O¯YSKACH KOBIET
Z NADCIŒNIENIEM INDUKOWANYM CI¥¯¥ (PIH)
STRESZCZENIE
Badania aktywnoœci dysmutazy ponadtlenkowej (SOD) przeprowadzono na
10 ³o¿yskach prawid³owych orz 15 ³o¿yskach kobiet ze zdiagnozowanym
nadciœnieniem indukowanym ci¹¿¹ (PIH). Wyniki naszych badañ wykaza³y ró¿nice
w aktywnoœci SOD w ³o¿yskach patologicznych w porównaniu do ³o¿ysk z ci¹¿
prawid³owych. Aktywnoœæ SOD w ³o¿yskach prawid³owych utrzymywa³a siê na
podobnym poziomie natomiast w ³o¿yskach patologicznych aktywnoœæ SOD
spada wzglêdem aktywnoœci SOD w ³o¿yskach prawid³owych. Zaobserwowano
pojedyncze przypadki wzrostu aktywnoœæi SOD w ³o¿yskach pataologicznych.
Uzyskane wyniki dotycz¹ce zmian w aktywnoœæi SOD w ³o¿yskach pacjentek ze
zmianami PIH potwierdzaj¹ udzia³ stresu oksydacyjnego w etiopatogenezie
nadciœnienia indukowanego ci¹¿¹.
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Received 2002.11.14.