Moran Statement on Study Providing Clues to Intersex Fish

Washington, D.C., June 3rd – Congressman Jim Moran, Virginia Democrat, issued the following statement regarding the U.S. Geological Survey’s (USGS) recent study that revealed clues as to the occurrence of intersex fish in the Potomac River.  The study found exposure to estrogen in fish reduces production of immune-related proteins, suggesting that compounds known as endocrine disruptors may make fish more susceptible to disease.

“This study provides new clues linking chemicals in our waters to the occurrence of intersex fish in the Potomac. Alarm bells go off when 80 percent of male bass in the Potomac River are found to produce eggs.  The USGS study brings a narrow focus and sharp conclusion that estrogen chemicals are negatively affecting our aquatic life. More studies are needed to further determine how man-made chemicals and compounds that are seeping into our lakes and rivers relate to the growing occurrence of intersex fish.”

Rep. Moran is the co-author of legislation with Rep. Jay Inslee (D-WA), the “Safe Drug Disposal Act of 2009” (H.R. 1191) which would allow local governments to devise prescription drug take-back programs, providing consumers an option to return unused medications rather than throwing them in the trash or flushing them down the toilet. Studies have shown that disposing of medications through flushing, such as birth control, may be causing an increase in potentially hazardous chemicals and compounds in our lakes, rivers and streams.

From this morning’s USGS press release on the new estrogen study:

The study, led by USGS genomics researcher Dr. Laura Robertson, revealed that largemouth bass injected with estrogen produced lowered levels of hepcidin, an important iron-regulating hormone in mammals that is also found in fish and amphibians. 

Besides being an important iron-regulating hormone, researchers also suspect that hepcidin may act as an antimicrobial peptide in mammals, fish and frogs. Antimicrobial peptides are the first line of defense against disease-causing bacteria and some fungi and viruses in vertebrate animals.

USGS researchers Drs. Vicki Blazer and Luke Iwanowicz have previously found intersex occurring in fish in the Potomac and Shenandoah rivers. Intersex is primarily revealed in male fish that have immature female egg cells in their testes. Because other studies have shown that estrogen and estrogen-mimicking compounds can cause intersex, the co-occurrence of fish lesions, fish kills and intersex in these two rivers suggested to USGS scientists that estrogen-mimicking compounds could be involved in the fish lesions and fish kills in addition to being a possible cause of intersex traits.  

That caused Robertson and her colleagues to investigate how estrogen could be affecting the immune system in these fish.  The study showed that largemouth bass produced two different hepcidin proteins.  Production of the first hepcidin protein was “turned down” by estrogen.  Production of the second hepcidin protein by fish exposed to bacteria was blocked by estrogen.  The fact that estrogen blocked production of hepcidins in fish exposed to bacteria gives more weight to the theory that estrogen or estrogen-mimicking chemicals could be making fish more susceptible to diseases, Robertson added.

Hepcidin could protect against bacterial infection in two ways.  “First,” said Robertson, “hepcidin could be an antimicrobial peptide that actually kills pathogens. Or it could be more complex. To live, a microbe must have iron, so when a microbe invades a person or animal, that microbe must obtain iron from its host. To ‘fight’ the microbe, a host can ‘suck up iron’ and store it in places inaccessible to the microbe. In mammals, hepcidin is a key player in how the host takes up and stores iron.”

The study, Identification of centrarchid hepcidins and evidence that 17β-estradiol disrupts constitutive expression of hepcidin-1 and inducible expression of hepcidin-2 in largemouth bass (Micropterus salmoides), was just published in the journal, Fish & Shellfish Immunology. The authors are USGS scientists Laura Robertson, Luke Iwanowicz and Jamie Marie Marranca.

For the USGS’s full report and press release, visit: http://www.usgs.gov/newsroom/article.asp?ID=2228&from=rss_home

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