الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Zearalenone (previously known as F-2 toxin) is a nonsteroidal oestrogenic
mycotoxin biosynthesized through a polyketide pathway by a variety of Fusarium fungi
which are common soil fungi in temperate and warm countries, and are regular
contaminants of cereal crops worldwide. Unexpectedly high concentration of mycotoxins
can be found in relation to the severity of the Fusarium infection. Toxin production mainly
takes place before harvesting, but may also occur post-harvest if the crop is not handled
and dried properly. Zearalenone is associated mainly with cereal crops, in particular:
maize; barley; oats; wheat; rice; and sorghum, together with their related products.
Although the mycotoxin is probably most common in maize, very high levels (11–15
mg/kg) can be found in other cereals, for example barley. In addition, Fusarium spp.
isolated from bananas can be capable of producing the mycotoxin. Zearalenone has also
been shown to be a potential contaminant of both amaranth and black pepper.
Gastrointestinal absorption determines the transition of mycotoxins from the lumen of the
gastrointestinal tract into the blood, and ultimately guides their distribution in the
organism. The absorption of Zearalenone took place mainly in the small intestines lumen,
particularly in the jejunum (from 70 to 85%) and ileum (from 30 to 15%). The excretion of
ZEARALENONE and its derivatives can be in bile, urine, but also milk. Urine and
faeces are the main routes of elimination of Zearalenone. Zearalenone is a phytoestrogen
demonstrating, due to the presence of a phenolic ring in its chemical structure resembling
the aromatic ring of ovarian-derived estrogens by its action it causes several functional
changes in the reproductive system, similar to naturally occurring estrogens. Moreover,
Zearalenone has also been shown to be hepatotoxic, haematotoxic, immunotoxic and
genotoxic.
Zearalenone is difficult to remove once generated. Because of its high thermal
stability, not destroyed by temperatures of 120 °C except at higher pH value. The best way
is the prevention of mycotoxin formation in the field, but this is often insufficient and other
strategies are needed. To decontaminate and/or detoxify mycotoxin-contaminated food and
feed, the most prevalent approach in the feed industry is the inclusion of sorbent materials
in the feed to obtain selective removal of toxins by adsorption during passage through the
gastrointestinal tract, or to add enzymes or microorganisms capable of detoxifying certain
mycotoxins. Organic binders are more efficient against a larger range of mycotoxins than
inorganic binders, which makes them more adapted to the most frequent cases of multicontaminated
feeds. Apart from that, they are biodegradable and do not accumulate in the
environment after being excreted by animals. It has recently been demonstrated that β-Dglucan
is directly involved in the organic binding process of Zearalenone.
Therefore, the present study aimed to investigate the protective effect of β-glucan
extracted from the edible mushroom Pleurotus ostreatus against Zearalenone toxicity and
their effect on total body weight, biochemical parameters, enzymatic activities and
antioxidant enzyme in male rabbits. Also, the changes in histopathological of testes, liver
and kidney. In the present study twenty male rabbits, approximately weighing 3 kg were
used. Animals were divided into four groups; five rabbits were kept as a control, five
rabbits received oral dose of β-glucan at 2 mg / kg B.W / day for 90 days, five rabbits
received an oral dose of 10 Ug/kg body weight standard Zearalenone and the last five
Summary
75
rabbits received oral dose of β-glucan (2 mg/kg body weight) + 10 μg/kg body weight
Zearalenone.
At the end of the experiment all animal were sacrificed and the following parameters
were determined:
1. Body weight.
2. Plasma glucose level.
3. Blood biochemical parameters and enzyme activities in plasma.
4. The activities of antioxidant enzymes.
5. Histopathological changes in testes, liver and kidney.
The results obtained can be summarized as follows:
1. Treatment with Zearalenone alone caused insignificant decrease in body weight
compared with control negative group. On the other hand, treatment male rabbits
with β-glucan and both Zearalenone and β-glucan showed significant decrease in
body weight.
2. Treatment with β-glucan caused a decrease in the plasma glucose level compared
to control negative group, on the other hand treatment of Zearalenone (control
positive) caused increase in plasma glucose level compared to control negative
which was not significant.
3. Treatment with Zearalenone alone significantly decreased SOD activity and
increase GPx activity compared to control negative group which was no
statistically significant difference. While the treatment with both of Zearalenone
and β-glucan returned the values of the previous parameters nearly to control
negative group.
4. Treatment with Zearalenone alone caused a significant increase in plasma urea
but insignificant increase in plasma creatinine, while plasma bilirubin
significantly decreased by 50% compared to control negative group. On the other
hand, treatment with both Zearalenone and β-glucan caused attenuated in plasma
urea and creatinine levels associated with Zearalenone, also resulted in an
improvement of the change in bilirubin value. While treatment with β-glucan
alone decreased plasma urea and bilirubin value and increased creatinine value
which was no statistically significant difference.
5. Treatment with Zearalenone alone caused a decrease in total protein, albumin
and globulin. While treating male rabbits with both β-glucan and Zearalenone
improved the value of the total protein and albumin nearly to control negative
group but the globulin value was not affected.
6. Treatment with Zearalenone alone significantly increased levels of ALT and
ALP. Also AST and LDH activity had increased which was no statistically
significant difference compared to control negative group. While treatment male
rabbits with both β-glucan and Zearalenone alleviated the effect of Zearalenone
on plasma enzymes. On the other hand treatment with β-glucan alone caused
insignificant increase ALT and ALP and decrease LDH but there was no visible
effect of β-glucan on AST activity.
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7. Treatment with Zearalenone caused significantly (P < 0.01) reduction the
percentages of cholesterol, plasma high density lipoprotein (HDL) and low
density lipoprotein (LDL), while triglycerides (TGs) and plasma very LDL
(VLDL) cholesterol levels were nonsignificant decreased compared to control
negative group. On the other hand, treatment with both Zearalenone and β-
glucan caused significantly decrease in TGs, cholesterol, LDL and VLDL
compared to control negative group, although the HDL value improved
compared to that of Zearalenone group. While treatment with β-glucan alone
significantly decreased cholesterol and LDL levels, also caused an insignificant
reduction in TGs, HDL and VLDL.
8. Zearalenone has induced many histopathological lesions in the testes, such as
decrease in spermatogenesis with mild basement membrane thickening. While it
caused marked morphological alterations as disturbance such as hydropic change
in hepatocytes with moderate portal fibrosis, portal inflammation and lytic
necrosis in the liver. Also caused loss of the normal architecture renal cells.
While treatment with both β-β-glucan and Zearalenone of male rabbits caused an
improvement in the histopathological distortion of testes, liver and kidney
sections.
Recommendations
• The present study showed that the supplementation therapy of β-glucan should
be used for the preventing of the toxicity caused by zearalenone and other
mycotoxins.
• Further studied are needed to confirm the protective efficacy of β-glucan as
dietary supplement for long-term therapy against zearalenone toxicity and the
potential inclusion in foods as a food additive.