Department of Biochemistry, College of Medicine, University of Lagos, Lagos, Nigeria
Author
Correspondence author
International Journal of Aquaculture, 2014, Vol. 4, No. 14 doi: 10.5376/ija.2014.04.0014
Received: 17 Feb., 2014 Accepted: 18 Mar., 2014 Published: 02 May, 2014
This is an open access article published under the terms of the
Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Bolawa et al., 2014, Endocrine Disruption by the Consumption of Fish (Tilapia oreochromis) from Heavy Metals Polluted River Sites and its Reversal Using Zinc, International Journal of Aquaculture, Vol.4, No.14: 85-88 (doi: 10.5376/ija.2014.04.0014)
Background: Metals can disrupt hormonal functioning by binding to the receptor site and this can lead to various hormonal changes.
Objectives: This research paper present the changes in hormonal levels due to the consumption of fish (Tilapia Oreochromis niloticus) gotten from heavy metals polluted riverine sources and its reversal using Zinc.
Methods: Twenty –one rabbits of mean weight 6.30kg were randomly grouped. The first group consists of seven rabbits and they were fed with 100g of fish (from Carter Bridge riverine site) together with rabbits pellets. The 2nd group was fed with100g of fish (from Makoko Riverine site) together with rabbits pellets while the third group which is the control group was fed with just rabbits pellets. The duration of the experience was three months. The level of hormones ( progesterone, LH, FSH, prolactin) were investigated using the serum. A similar experiment was conducted on another set of twenty-one rabbits grouped and fed in the same way as the previous set but this time the second group consists of rabbits fed100g of fish ( from Carter bridge site) together with rabbits pellets and0.133g of zinc. Also the levels of hormones were investigated.
Results: Progesterone levels significantly decreased from 1.60 ± 0.05 to 0.03±0.01 while FSH level also decreased from 1.60±0.02 to 1.10±0.05. The ratio of FSH to LH was greatly altered. Prolactin levels increased significantly from 1.10±0.02 to 1.80±0.03. The progesterone levels of zinc supplemented rats shoots up from 17.00±1.88 to 27.00±2.98.
Conclusion: Data of this study suggest that ingestion of fishes from heavily polluted sites by animals is capable of inducing low progesterone levels and prolactinaemia which can lead to infertility. Also the ingestion of a daily supplement in form of zinc can reverse this change.
Endocrine disruptors are substances that interfere with the synthesis, secretion, transport, binding or elimination of natural hormones in the body that are responsible for the maintenance of homeostasis, reproduction, development and or behavior. Many endocrine disruptors are thought to mimic hormones. They have chemical properties similar to hormones that allows binding to hormone specific receptors on the cells of target organs. Endocrine disruptors include pesticides, dioxins, polychlorinated biphenyls (PCBS), heavy metals, phenols etc (EPA, 1998).
Health effects attributed to endocrine disrupting compounds include a range of reproductive problems (reduced fertility, reproductive tract abnormalities), changes in hormone levels, early puberty, brain and behavior problems, impaired immune functions and various cancers (Crisp et al., 1998; Krimsky, 2001). Hormones travel throughout the body and act as chemical messengers. They interface with cells that contain matching receptors in or on their surfaces. The hormones bind with the receptor. The endocrine system regulates adjustments through slower internal processes, using hormones as messengers. The endocrine system secretes hormones in response to environmental stimuli and to orchestrate development and reproductive changes. The adjustments brought on by the endocrine system are biochemical, changing the cell chemistry to bring about a long term change in the body. These systems work together to maintain the proper functioning of the body through its entire life cycle. Hormones work at very small doses (Krimsky, 2001).
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.
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Table 1 Prolactin, Progesterone, LH & FSH hormones in serum of rabbits fed with Tilapia Fish diet from Carter Bridge & Makoko water sites
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In the second set of the research work carried out, progesterone levels of zinc supplemented rabbits increased significantly from 0.03 ± 0.02 to 6.80 ± 0.70 (Table 2).
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Table 2 Serum progesterone levels of rabbit fed contaminated fish & zinc supplemented diet
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3 Discussion
This study confirms the fact that heavy metals together with other environment pollutants are endocrine disruptors since they interfere with the level of progesterone, lutenizing hormone and follicle stimulating hormone. As the level of environment pollutant increases, the levels of progesterone & FSH decreases greatly while the levels of FSH and LH is being altered. This may lead to early menopausal period and infertility in females (Lafuente & Esquifino, 1998).
Marie et al. (2001) investigated the effect of Lead on the system in lead smelter workers. Median level of lead in plasma ranged from 0.04-3.7µ/dl in the active lead workers. FSH levels were lower in the lead workers than in the control group indicating an effect of lead at pituitary level. Moderate exposure to lead was associated with minor changes in the male endocrine function particularly affecting the hypothalamic – pituitary axis (Lafuente & Esquifino, 1998; Lafuente et al., 2005). This study is in agreement with the present study which found low levels of FSH in the rabbits being studied. Lafuente & Esquifino (1998) found out that cadmium modify amine metabolism at the CNS & pituitary hormone secretions.
This xenobiotic (cadmium) is associated with deleterious effect on the gonal function and with changes in the secretory pattern of other pituitary hormones like prolactin, ACTH & TSH. Lafuente et al. (2004) analyzed the effect of cadmium on plasma level of LH, FSH in rats. They reported that the metal exposure abolished daily pattern of plasma LH levels. In 2005, they studied the effect of cadmium on prolactin secretion in rats and observed that the cadmium exposed animals exhibited variations in plasma prolactin levels. These finding are inline with this present study which found altered level in LH & prolactin levels in the experimental animals studied.
Some of the most dangerous emerging disease facing the society today are directly related to exposures to deadly environmental towns. Exposure to heavy metal toxins such as lead is linked with a 46% increases in the mortality rate according to the Centre for Disease Control in Atlanta, USA.
From the study, it was observed that rabbits fed with zinc supplements had an increase in serum progesterone level when compared with the control and the group which had no supplement in their diet. Zinc supplement do reverse heavy metal effects in the rabbits as seen from this study. It also increases the production of progesterone thereby enhancing ovulation in female rabbits. With zinc supplement, adverse effects from the consumption of heavy metal contaminated fish can actually be managed. This also suggests the fact that zinc supplement may enhance ovulation as evident from the increase in progesterone levels.
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