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Using Fish to Detect Estrogen-like Endocrine Disruptors October 15, 2010

Posted by Grace Dible in Biology, Chemistry, Ecology, Environment/Conservation, Genetics, Health, Medicine, Physiology.
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Endocrine disruptors, according to the EPA, are substances which mimic a hormone, stimulate a body to over respond to a stimulus, cause hormones to respond at inappropriate times, or cause an under/over production of a hormone.  The EPA is most concerned with endocrine disrupting chemicals that end up in the environment and affect the environment and wildlife.  Chemicals of more recent concern are synthetic, natural, and mimic estrogens.  These chemicals include 17α-estradiol (found in birth controls) and herbicides like atrazine.  Much of the recent research is trying to determine whether or not these endocrine disruptors are causing intersex fish, which could possibly lead to population declines.

This flow chart shows how endocrine disruptors may lead to sex changes in a fish population.

One way to determine the estrogenic endocrine disruptors in an aquatic environment is to use different transgenic fish as biomarkers, specifically zebrafish (Danio rerio) and medaka (Oryzia latipes).  Current research is underway in order to determine the affects of these different endocrine chemicals on bioactivity.  Both Medaka and Zebrafish can be transgenic with different fluorescent proteins, which were originally found in bioluminescent jelly fish.    At Marian University in Indianapolis, I am currently trying to determine the best methods for determining the affects of estrogen-like endocrine disruptors in transgenic medaka with green fluorescent protein (GFP).  This GFP is expressed in the liver of the fish when a large amount of vitellogenin, an estrogen inducible promoter, is in its system.  Ordinarily, vitellogenin is found in the female medaka liver, but if an endocrine disruptor is in the environment, then a male medaka may be able to express the GFP as well; the GFP is these medaka have a 100% binding affinity to 17α-estradiol.

Medaka fish expressing GFP in the liver

According to recent review on the effects of a supposed endocrine disruptor like atrazine (A Qualitative Meta-Analysis Reveals Consistent Effects of Atrazine on Freshwater Fish and Amphibians – Jason R Rohr and Krista A McCoy – January 2010  Environmental Health Perspectives), they “found little evidence that atrazine consistently caused direct mortality of fish or amphibians, but we found evidence that it can have an indirect and sublethal effects.”  These sublethal effects in fish may include a decrease in motor skills, perceiving predator risk, olfactory sensitivity, and gonadal morphology.  Atrazine may also lead to the body’s production of aromatase, an enzyme that converts testosterone into estrogen.   Studies still need to be done to see if this supposed endocrine disruptor is causing the fish population sex ratios to change or the production of aromatase.

How could this research be beneficial to human health?  Waste water treatment plants currently don’t filter out estrogen-like endocrine disruptors. Right now Dr. Paul Winchester, at the Indiana University School of medicine, is trying to determine whether there is a correlation between the supposed endocrine disruptor atrazine and birth defects.  Another focus of the research is whether or not areas with high amounts of atrazine can lead to higher rates of breast, ovarian, and prostate cancer.   Dr. Paul Winchester recently did an interview with Indianapolis based NUVO magazine to help spread information on this endocrine disruptor so that people are more aware of what is in drinking water.

To see his Dr. Winchester’s full interview click here.  To view the EPA statements on endocrine disruptors click here.

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