Genistein: effect on the ion transport of the intestine of seawater adapted, Anguilla anguilla.

Genistein is a phytoestrogen belonging to the class of isoflavones. Like other phytoestrogens it is considered as an ambient contaminant that can reach the aquatic environment by sewage treatment plant and pulp mill effluents or wasterwater in which they are present as pharmaceutical compounds. These substances can have deleterious effects on the reproductive system of fish, due to their structural similarity with estrogen. The investigations of the effects of pollutants on the European eel (Anguilla anguilla) is of great interest because this species can bioccumulate large amounts of lipophilic contaminants that can reach toxic concentrations when the fish utilize the stored fat, thus contributing to the observed decline of eel stocks. In this study we investigated the effects of the phytoestrogen genistein on the ion transport of the intestine of A. anguilla adapted to sea-water, since it was shown that this substance can affect different membrane ion transporters. For this purpose we tested the effect of the isoflavone on the transepithelial (Isc= short circuit current and gt= transepithelial conductance) of the isolated intestine by employing Ussing chamber experiments. We showed that genistein reduced Isc at all the concentrations tested (from 10-6 M to 10-4 M) with a maximal effect observed with 10-4 M genistein. Experiments performed with known inhibitors of ion transporters suggested that the cotransport Na/K/2Cl is the target of the isoflavone. In view of the important role played by this transport mechanism in the adaptation of the animal to seawater, we conclude that the phytoestrogen can have deleterious effects on this fish species, not only by interfering with the endocrine system, but also by impairing osmoregulation