WASHINGTON, June 3 (UPI) -- U.S. scientists have found exposure to estrogen reduces the production of immune-related proteins in fish, making them more susceptible to disease.
U.S. Geological Survey researchers Laura Robertson, Luke Iwanowicz and Jamie Marie Marranca said their findings provide new clues for why intersex fish, fish kills and fish lesions often occur together in the Shenandoah and Potomac rivers.
The study, led by Robertson, revealed largemouth bass injected with estrogen produced lowered levels of hepcidin, an important iron-regulating hormone in mammals that's also found in fish and amphibians.
The scientists said they suspect hepcidin might also act as an anti-microbial peptide in mammals, fish and frogs. Anti-microbial peptides are the first line of defense against disease-causing bacteria and some fungi and viruses in vertebrate animals.
"Our research suggests that estrogen-mimicking compounds may make fish more susceptible to disease by blocking production of hepcidin and other immune-related proteins that help protect fish against disease-causing bacteria," said Robertson.
The study -- the first demonstrating control of hepcidin by estrogen in any animal -- appears in the journal Fish & Shellfish Immunology.
