Scientists have found that fish exposed to estrogen produce fewer immune-related proteins.
Laura Robertson, Luke Iwanowicz and Jamie Marranca studied the effects of estrogen exposure in largemouth bass (Micropterus salmoides) and published their findings in a recent issue of the journal Fish and Shellfish Immunology.
The authors injected estrogen into the fish and studied the expression of the hepcidin gene (hepcidin is an important iron-regulating protein in mammals also found in fish).
It has been suspected that hepcidin functions as an antimicrobial substance in fish.
The largemouth bass produces two different kinds of hepcidin protein, and the authors found that estrogen decreases the production of one form of hepcidin (by decreasing expression of the gene) and blocks the production of the second form.
According to the authors, Estrogen and EEDCS have been shown to modulate the immune response in fish. It is likely that they interfere with the expression of genes involved in innate immunity, thus potentially increasing susceptibility of fish to bacterial infection.
This may explain why the Potomac and Shenandoah rivers, which have elevated levels of estrogen and EEDCs have increased occurrences of fish lesions and fish kills.
For more information, see the paper: Robertson, LS, LR Iwanowicz and JM Marranca (2009) Identification of centrarchid hepcidins and evidence that 17-estradiol disrupts constitutive expression of hepcidin-1 and inducible expression of hepcidin-2 in largemouth bass (Micropterus salmoides). Fish and Shellfish Immunology 26, pp. 898"907.