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Endocrine Disruptors: Atrazine. Jonathan Shalom Dr. Blumberg Bio Sci 2B April 20 th , 2005 . What is the Endocrine System and what is its purpose?. Composition of many glands (ovaries, testes, thyroid, parathyroid, adrenal)

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Endocrine disruptors atrazine l.jpg

Endocrine Disruptors: Atrazine

Jonathan Shalom

Dr. Blumberg

Bio Sci 2B

April 20th, 2005


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What is the Endocrine System and what is its purpose?

  • Composition of many glands (ovaries, testes, thyroid, parathyroid, adrenal)

  • Some of these glands secrete hormones while others produce chemicals or fluids.

  • Hormones produced by the endocrine glands enter the capillaries of the blood circulatory system. They trigger different effects by targeting specific "receptors" in the organs.

  • The ES is important because it coordinates and regulates many essential body functions

    Examples:

  • reproduction and embryo development;

  • production, use and storage of energy;

  • balance and maintenance of water and salt (electrolytes) in the body; and

  • reaction to stimuli (e.g., fright, excitement).


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Some Examples of Common Hormones

  • Examples of hormones secreted by the ES that would effect the biological function of an individual :

  • ACTH (adrenocorticotrophic hormone) - produced by the pituitary gland to influence the release of corticosteroid hormones from the adrenal glands,

  • ADH (anti-diuretic hormone, vasopressin) - produced by the pituitary gland to stimulate water reabsorption by the kidney tubules

  • Adrenaline (epinephrine) and noradrenaline (norepinephrine) - two hormones formed in the adrenal gland that help the body to react (e.g., flight or fight, body defense mechanisms) under stressful conditions (they can increase the heart rate, blood pressure, blood sugar levels, blood clotting rate),

  • Estrogen - a female sex hormone produced by the ovaries,

  • Insulin - secreted by the pancreas and regulates the storage and use of carbohydrates in the body

  • Thyroid Hormone - produced in the thyroid and influences the function of virtually every cell in the body (growth, development and metabolism).

    Source: http://www.ccohs.ca/


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Disruption of the ES

The Endocrine System may be disrupted in one of three ways:

  • A substance may imitate a natural hormone and lock onto a receptor within the cell.

  • A substance can bind to a receptor within a cell and thus prevent the correct hormone from binding.

  • The disruptors can interfere or block the way natural hormones and receptors are made or controlled.


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Atrazine: Profile

Purpose: Used as an Herbicide/ Pesiticide to control grasses and broadleaf weeds

Other Chemical Names: 1,3,5-Triazine-2,4-diamine, 6-chloro-N-ethyl-N'-(1-methylethyl)- , 1-Chloro-3-ethylamino-5-isopropylamino-2,4,6-triazine,etc.

Toxicity: Termed PAN Bad Actor Chemical

Physical Appearance: White powder that is not very volatile, reactive, or flammable and that will dissolve in water.


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Atrazine: Connection with Environment

  • Primarily enters environment through spraying on farm crops.

  • Atrazine is taken up by the plants growing in the soil or is broken down over a period of days to months.

    or

  • It may wash from the soil into streams where it will stay for a long time

  • If atrazine enters the air, it may be broken down by reactions with chemicals in the air, or it may adhere to particles such as dust which eventually settle out of the air.


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The Problem

  • Leopard frogs are in the middle of mating season when farmers are using herbicides

  • Atrazine water levels are highest when frogs are going through critical stages of development

  • Frogs and other amphibians living in waters with high Atrazine levels were found to have multiple gonads and altered sexual development


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Exposure to Atrazine

  • Inhaling: The intake of dust (commonly by rural residents). If their water supply is contaminated, they could breathe atrazine as they cook, bathe, or do laundry.

  • Ingestion: People who have contaminated drinking water may be exposed to low levels of atrazine. Some low-level exposure to atrazine may occur when treated crops are eaten or handled. People who handle contaminated soil could ingest traces of the herbicide if they eat or touch their mouths with dirty hands.

  • Touching: Atrazine is not absorbed through the skin


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Chemical Process

  • Receptors, which are incorporated into the plasma membrane, are proteins that function as ligand-activated transcription factors. They regulate the formation of proteins in many tissues.

  • Some ligands can bind to several different nuclear receptors. Also, despite the conservation of receptors, individual ligands induce expression of different biological responses in different species and tissues.


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Process: Part 2

  • According to research, data supports the hypothesis that a hormone diffuses to the cell nucleus, binds non-covalently to the Endoplasmic Reticulum, dimerizes, and changes shape.

  • The shape allows it to attach to one of many potential DNA docking sites

  • The attachment triggers the formation of a transcription complex and activates a specific gene in the body.

  • Substances, such as atrazine, prevent this binding, and therefore cause deformities among organisms.

  • Since the endocrine disruptor already takes up the original location of the hormone (activation site), the hormone continues to try to attach itself to the cell.

  • However, after failing to attach itself to the original cell, the hormone seeks a new cell to attach to, which results in an abnormal accumulation of hormones.


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Phenotypic Effects On Organisms

  • Atrazine could affect pregnant women by causing their babies to grow more slowly than normal or by causing them to give birth early.

  • Atrazine has been shown to slow down the development of fetuses in animals, and exposure to high levels of atrazine during pregnancy caused reduced survival of fetuses

  • Atrazine has been shown to cause changes in blood hormone levels in animals that affected ovulation and the ability to reproduce. These effects are not expected to occur in humans because of specific biological differences between humans and these types of animals.

  • Atrazine also caused liver, kidney, and heart damage in animals; it is possible that atrazine could cause these effects in humans, though this has not been examined.

  • Not enough information is available to state whether atrazine causes cancer in humans. There may be a link between atrazine use and various types of cancer, but we still do not know.


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Controls to Endocrine Disruptors

  • The majority of the more than 2,000 chemicals that come onto the market every year do not go through even the simplest tests to determine toxicity.

  • Therefore, many governments are implementing new laws requiring strict testing on new chemicals to help humanity and the environment.

  • Will be banned in all European countries by 2005

  • Environmental Protection Agency has only placed a limit on Atrazine use in the United States and has not banned it entirely



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Interesting Facts

  • Atrazine is one of the most widely used herbicide in the U.S. Between 74-80 million pounds of atrazine are used each year in the U.S.

  • The U.S. Environmental Protection Agency has identified 200 community water systems where atrazine has been detected at levels that approached or exceeded the agency's Maximum Contaminant Level (MCL). Of the 200, eight community water systems have annual average readings that significantly exceed the MCL.

  • In 1995, more than 80 percent of atrazine applications -- nearly 54 million pounds -- were applied to U.S. corn crops.

    Source: http://www.checnet.org


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What Can You Do?

  • Learn and research about endocrine disruptors, and spread the word to your family and friends.

  • If possible, buy organic foods.

  • Instead of using pesticides to kill pests, use traps or baits as a substitution.

  • Keeping your house clean can prevent the invasion of pests.

  • Make sure the fish that you eat from lakes or rivers are not contaminated.

  • Avoid heating food in plastic containers

  • Do not give young children soft plastic or toys



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