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International Journal of Aquaculture, 2014, Vol.4, No.13 79
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84
http://ija.biopublisher.ca
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Endocrine disruption can thereby also occur from
low-dose exposure to hormonally active chemicals
that can interfere with receptors (Krimsky, 2001).
Heavy metals are incorporated through food ingestion
& inhalation. Lead is commonly used in different
industrial area e.g. print, paint, and fuel industry and
may dissolve from leaded pipes used for drinking.
Cadmium is ingested with food, such as fish, seafood,
fungicide, herbicides & wood preservatives. Exposure
to heavy metals has been reported to either enhance or
inhibit the biosynthesis of progesterone (Ng & Liu,
1990). Heavy metals induce modifications of
neurotransmitter in the CNS and impair the
hypothalamic release of gonadotropin – releasing
hormone (Foster et al., 1993; Lakshmana et al., 1993).
Thus the hypothalamic – pituitary – ovarian axis can
be affected by heavy metals either directly or
indirectly through modifications of the secretion of
prolactin, adrenocortical steroids or thyroid hormones.
In the ovary itself, accumulation of heavy metals
impairs the production of estradiol and progesterone
(Piasek & Laskey, 1994).
Problem Statement
Hundreds of people each year catch and eat fish from
Carter Bridge and Makoko Riverine sources which is
contaminated with chemicals and heavy metals that
can be harmful to human health. High levels of heavy
metal have been detected in Tilapia fish gotten from
this area (Bolawa & Gbenle, 2010; Bolawa and
Gbenle, 2012). This may pose a great health hazard
especially with long term exposure.
What is the fate of the people consuming these fishes?
Is there any remedy to these negative effects?
1 Materials and Methodology
The effect of the consumption of heavy metal
contaminated fish (
Oreochromis niloticus
) on hormonal
levels in laboratory animals were determined.
21 experimental female rabbits were obtained from
the Nigerian Institute of Medical Research, Yaba,
Lagos State, Nigeria. The rabbit were fed with rabbit
pellets manufactured by Pfizer Livestock Feeds Plc,
Ikeja, Lagos State.
The rabbits were allowed to acclimatize to laboratory
condition in well – ventilated cages for two weeks.
The animals were grouped into three, with each group
containing seven rabbits. Tilapia fish (
Oreochromis
niloticus
) samples were obtained from Carter Bridge
water site and Makoko water site. These study sites
were selected because of their commercial
significance. The fishes were dried in the oven &
weighed. The first group of animals consists of seven
rabbits and they were fed with 100g of fish (obtained
from Carter Bridge water site) together with rabbit
pellets. The second group of animals consists of seven
rabbits and they were fed with 100g of fish from
Makoko water site together with rabbit pellets while
the third group which is the control group was fed
with just rabbit pellets. The duration of the experiment
was 3 months. The level of hormones (progesterone,
LH, FSH, Prolactin) was investigated using the
blood samples.
A similar experiment was conducted on another set of
21 female rabbits grouped and fed the same way as the
previous set but this time the second group consists of
rabbits fed with 100g of fish (from Carter Bridge
water site) together with rabbits pellets and 0.133g of
zinc supplements. The level of progesterone was
investigated.
2 Results
In the first set of the research work carried out,
progesterone levels decreased significantly from 1.60 ±
0.03 to 0.03 ±0.01( Table 1). The ratio of FSH to LH
was greatly altered. Prolactin levels increased
significantly from 1.1 ±0.02 to 1.80 ±0.03.
Table 1 Prolactin, Progesterone, LH & FSH hormones in serum of rabbits fed with Tilapia Fish diet from Carter Bridge & Makoko
water sites
Study location groups
Prolactin (ng/ml)
Progesterone ng/ml
LH IU/ml
FSH IU/ml
Carter
1.80 ±0.03
a
0.03 ±0.01
a
3.80 ±0.01
a
1.40 ±0.01
Makoko
1.60 ±0.05
a
0.30 ±0.05
a
4.00 ±0.02
a
1.10 ±0.05a
Control
1.10 ±0.02
1.60 ±0.03
1.10 ±0.05
1.60 ±0.01
Note: Value rep. mean ±S.E.M. (n=5);
a
P< 0.05 ANOVA