Sumpter suspects that breakdown products of detergents are disrupting the endocrine systems of the fish. Studies are being done in the lab to verify this idea and field studies of free ranging fish in U.K. rivers are underway. Probably not, say researchers. From what endocrinologists and toxicologists already know about hormones, they propose the following general scenario for disruption. The chemical culprits dock at special sites called receptors, which are located in an animal's cells.
Receptors usually are picky about what they allow to bind.
Receptors that would normally accept only estrogens or androgens floating around in the body might accidentally bind a chemical that mimics the receptor's true match. The attachment of the foreign chemical prevents the resident hormones from doing their normal jobs. In the case of the alligators, Guillette suspects that DDE binds to the animals' androgen receptors and prevents androgens from doing their masculinization work. The findings, published in the British scientific journal Nature in June, demonstrate that DDE is indeed an anti androgen, say William Kelce and Earl Gray, EPA researchers who led the study. They found that DDE prevented androgens from binding to human androgen receptors in cultured cells, and male rats exposed to DDE had physical abnormalities in reproductive parts.