It is said that certain compounds, known as endocrine disruptors, may make fish more susceptible to disease. This research is said to provide more information one why intersex fish, fish krills and fish lesions often occur together in the Shenandoah and Potomac rivers. 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.
Researchers found 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. Robertson said 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.
USGS researchers Drs. Vicki Blazer and Luke Iwanowicz have previously found intersex occurring in fish in the Potomac and Shenandoah rivers. 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.
It is told that hepcidin could protect against bacterial infection in two ways. Robertson said that 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.
