Rapid growth and development of cities created various bio-environmental
problems for inhabitants. One of the most important problems of living
in big cities in present and future for small cities is pollution.
Air pollution is a permanent and serious threat for cities and leads
to dangerous effects on health and society health and cause considerable
economic suffers (Zhang et al., 2007).
Given the statics and data use of fossil fuel had an ascending growth
in transport and to the same extant is the growth of the various pollutant
in the air.
In 2000 transport section played important great role in pollution and
had spread to 60.2% Azot oxides, 22% Sulfur dioxide, 98.3% Carbon mono
oxide, 90% Hydrocarbons and 75% dust.
Sulfur dioxide (SO2) is one of pollutant of the city air
that in low density in city air and in high density in industrial environments
was found (Qin and Meng, 2006; Bai and Meng, 2005; Meng and Liu, 2007).
In 1992 international cancer research agency classified SO2
to be one of carcinogen materials (Pesatori et al., 2006).
Pollution produced by fossil fuel rich with sulfur increase the death
rate especially death of inspiratory and cardiovascular disease (Hedley
et al., 2002).
Exposure to high amount of SO2 is dangerous. Exposure to gas
with the density of 100 ppm threat the health. Exposure to air pollutant
may cause irreversible changes in activity of inspiratory system and dose
effected with asthma are more in danger (Islam and Oberbarnsheidt, 1994).
Apart from cases above, effect of other synthetics of SO2
like sulfite and sulfate on hypo cay neurons has been studied and results
revealed that SO2 synthetics cause increase of irritability
of theses neurons (Du and Meng, 2004).
Exposure to SO2 cause chronic disorder and change of activity
of lungs. Although air pollutant enter the body by inspiratory system
and the major effect of them is on lungs but other organs harm, too. Disease
of cardiovascular (Pope et al., 2003), lung cancer (Zhang et
al., 2007; Matsumoto et al., 2007) especially in women (Hwang
et al., 2007; Soll-Johanning et al., 1998), kidney and
bladder pharynx and larynx (Soll-Johanning et al., 1998), gaster
and prostate (Berndt, 1977), skin and rectum even in some cases liver
(Soll-Johanning et al., 1998), decrease of body abilities, decrease
of IQ in children mostly for precipitation of Pb and decrease of life
span and miscarry (Hafez et al., 2001) in pregnant women are among
the result of the air pollution on health of human. The aim of present
study was to investigate the histopathological effect of sulfur dioxide
(SO2) on the mouse liver in acute and chronic exposure.
MATERIALS AND METHODS
First 28 suri mice with the average weight of 30 g were randomly selected
and divided into four groups. One as control group that mice were not
exposed to gas. Second groups were exposed to gas with a high dose (100
ppm) just once. Third and fourth groups selectively for one and 3 weeks
were exposed once in a day and for 5 min with the low dose of gas (20
Mice of each group in a special cage with the sizes of 10x20x40 cm. Gas
was produced outside of the cage in special system and by an elastic pipe
was led inside the cage (Sheal method). SO2 gas was produced
by this chemical reactions:
Na2SO3+2HCl → 2NaCl+SO2+H2O
Weight of the salt and the volume of the acid given the specialities
an condition of the materials like concentration degree, acid percentage
was determined and condition like temperature and pressure, were considered.
In all groups mice were unconscious by the dislocation of the cervical
vertebral and their liver was removed. First macroscopic observation and
then microscopic evaluation was carried out. For microscopic evaluation
samples of liver was prepared and kept in formalin 10%. After fixation
and embedding, serial sectioning was done and from each sample 5 section
were selected (section number 5, 8, 11, 14 and 17). After staining with
H and E, microscopic slide were prepared.
Statistical tests: Among prepared sections in each group 10 slide
and from each slide randomly 5 microscopic field were selected. Macrophages
in each microscopic fields were counted; then information of the acute
and chronic one and three week by t-test with the control group were compared.
In normal condition liver has hyaline tissue that is rather soft. In
microscopic observation and slide of control group, hepatocytes in a radial
style they are placed from centra lobular to the periphery and most of
them were mononucleous and sometimes dinucleous forms were seen among
them (Fig. 1).
||Microscopic section of chronic group radicalic hepatocyte
||Microscopic section of acute liver group the ressels
were hyperaemic (x4)
In macroscopic studies of acute group, hemorrhagic spots on the surface
of liver was seen. Lobules were morphologically changed in microscopic
In each control and acute groups 50 samples were studied and compared
in number of kupffer cells.
Average number of cells in control group was 7 ± 1.4 and in acute
group was 9 ± 1 and statistical test revealed significant difference
between them (p<0.0001), hyperemia of vessels was seen noticing the
photomicrographs (Fig. 2). Results in chronic stages
1 and 3 weeks were almost similar. LM studies showed darkening of the
liver tissue and increase of the stiffness was observed.
Hemorrhagic spots on the liver surface were seen. In this group the lobules
were morphologically changed, number and diameter of the blood vessels
were increased, hyperemia and angiogenesis that are symptoms of important
of the harms caused by gas, were seen clearly in the photomicrographs.
Diameters of the blood vessels in both chronic groups were considerably
increased (Fig. 3).
||Microscopic section of chronic 1 week liver group comparative
||Microscopic section of chronic 3 weeks liver group hepatocyte
with big light nuclei indicator of malignancy (x100)
Morphologic change of hepatocytes and increase in becoming eosinophil
that was the sign of cellular necrosis was observed. Hepatocytes with
large and clear and extant euchromatin region was observed. It showed
beginning of the malignant and precancer stages in that tissue (Fig.
Evaluation of the number of kupffer cells between two control and chronic
1 week group, in each group 50 microscopic field with the magnification
of the 100 were observed. Average of cell in control group were 7 ±
1.4 and in chronic group of 1 week were 10 ± 1. The statistical
test showed difference between average cells in this two groups (p<0.0001).
Average number of the kumfer cells in control group 7 ± 1.4 and
in chronic group of 3 weeks were 11 ± 1.2. Statistical tests showed
significant difference between average cells in these two groups (p<0.0001).
Here, acute group lobules were morphologically changed and lost their
normal structure. Hyperemia of vessels were observed.
This study corresponded of the results of histopathologic effects of
the sulfur mostart on large mouse of laboratory.
The number of kupffer cells increased considerably in acute group. It
may be due to increase of phagocytic activity caused by letting in the
Macroscopic observation of chronic groups showed darkened liver tissue
and increased stiffness. Hemorrhagic spot on the liver surface seen.
In studies of chronic groups showed that structure of the lobules were
changed. Number and diameter of the blood vessels were increased, hyperemia
of vessels were observed in photomicrographs.
These results also proved by other investigators. They reported hyperemia
and dilation of the sinusoids, destroy of the lobules, limitation and
disformation of liver cord.
This study, demonstrated angiogenesis in chronic groups that is a sign
of damage of vessels under the gas inspiration.
Cellular changes similar increase of the number of macrophages and hepatocyte
Increase of the number of macrophages may be due to the increase of phagocytotic
activities caused by the gas inspiration. Macrophages producing cytokines
are pre-inflammation factors. kupffer cells that is the member of the
mononuclear phagocytes demonstrated more and may be due to inflammation
by the gas.
Another scientist reported that polluted air increased pulmonary macrophage
(Van Eeden et al., 2001). This study reveled the increase of eosinophilic
characteristic of hepatocytes. Probably is the due to necrosis of mentioned
Hepatocytes observed with large and clear nuclei (high concentration
of euchromatins). It showed the beginning of the malignant and pre-cancer
mood of the tissue, probably.
These results were proved other researches, who studied the effect of
SO2 on different tissues ( like: brain, lung, heart, liver,
spleen, thymus, bone marrow and kidney).
They exposed the experimental group of rats during 7 days to SO2
with density of 125, 250 and 500 mg kg-1 of weight. These results
of this experiment showed that SO2 caused destroy of the DNA
of these cells.
This results offered that exposure to this gas cause cancer and destroy
of DNA (Meng et al., 2004).
They revealed that SO2 with the density of 28 and 56 mg m-3
cause considerable increase in mRNA rate of P53 genes and bax in liver
of suri mice; where as mRNA gene bcl-2 had considerably decreased.
This results showed that exposure to SO2 gas cause changes
in gene express rate that are responsible for apoptosis and suggest this
gas can induce apoptosis in liver (Bai and Meng, 2005).
Researchers in 2007 showed that, inhaling of SO2 gas with
the density of 56 mg m-3 caused pathologic changes of liver
cells of the suri mice.
These changes were inflammation of nucleus, fat droplets, degeneration
of mitochondria and dilation of rough endoplasmic retinaculum rER (Meng
and Liu, 2007).
Another study revealed that reduced gluthation rate to oxidate gluthation
was considerably decreased in liver and other mice organs.
Decrease of the reduced gluthation rate and the ratio of the reduced
gluthation to oxidate gluthation suggested that cytotoxic effects with
decreased the antioxidant and weakened of the immunosystem and antioxidant
in biological systems.
Evaluated the Meng (2003) effect of SO2 on enzyme rate like
catalase, gluthation peroxidase, superoxide dismutase and gluthation that
has important role in decrease of free radicals.
Results showed that inspiration of SO2 cause considerable
decrease in gluthation peroxidase and superoxide dismutase activity rate
in 9 organs of mice (brain, lung, heart, liver, stomach, spleen, kidney,
small intestine, testis ) (Meng, 2003).
Qin and Meng (2006b) studied inhalation effects of the SO2
gas with the density of the 14.11, 28.36 and 96.25 mg m-3 during
7 days and daily for 6 h on activity rate of de alkinase pentoxirezophorine
and nitrophenol hydroxylase of lung and liver of male rats was considerably
decreased, but nitrophenol hydroxylase rate just in lung of these rats
decreased (Qin et al., 2006).
Gumuslu et al. (1998) evaluated the inhalation effects of the
SO2 with the density of the 100 ppm during 10 days and daily
to 1 h on the activity rate of the erythrocyte antioxidant showed that
SO2 gas causes lipid peroxidation and also cause increase of
the activity rate of erythrocyte antioxidant enzymes (Gumuslu et al.,
1998). Gumuslu et al. (2000) studied the inhalation effects of
SO2 on plasma amount of vitamin C and rat Seroluplasmin, results
showed that plasma vitamin C and rat Seroluplasmin in young rats, adult
and old that were exposed to the SO2 was increased (Geng and
Based on the enzyme study and results this study concluded that cytotoxic
effect of SO2 can cause malignancy and cancer by decrease of
the antioxidants and suppression of the immunosystem (Geng and Meng, 2003).
Clinic studies and laboratory evaluation showed relationship between
the amount inhalation of particles and floating of polluted air and waterfall
process of coagulation reactions, pellets activity and development of
atherosclerosis and thrombose, these negative effects, by making free
neurotransmitters of solution by lungs that affect the coagulation parameters
or by direct transfer of the particles to the circulary and or direct
effect on the heart autonome control system (Nemmar et al., 2006).
Recent results of the scientists, showed considerable increase of the
endothelin vasoactive peptide in circulary in rats exposed to the polluted
air (Vincet et al., 2001).
Another study revealed that exposure to the polluted air with increasing
the surface of the active C-protein (Peters et al., 2001a), systemic
inflammation that was an important sign for the cardiovascular disease
(Ridker et al., 2002), inflammation damages of the lungs (Ghio
and Devlin, 2001; Souza et al., 1998), responses of the bone marrow
and blood cell (Tan et al., 2000), increase of the lung macrophages
cells that produce pre-inflammation cytotoxin. Increase of the blood plasma
viscosity (Peters et al., 1997), bad effect of the vessels endothelium
activity (Brook et al., 2002) and infarcts (Peters et al.,
Inflammation reaction caused by floating dust of polluted air in study
of the laboratory animals was seen (Mukae et al., 2001).