MULTIXENOBIOTIC RESISTANCE IN URECHIS-CAUPO EMBRYOS - PROTECTION FROMENVIRONMENTAL TOXINS

Urechis caupo is a marine worm that lives and reproduces in sediments containing a variety of potentially toxic environmental chemicals (xen obiotics). Its embryos have a multixenobiotic transporter, which is si milar to the multidrug transporter in mammals, as indicated by their a bility to transport a variety of moderately hydrophobic compounds such as dyes, drugs, and pesticides out of the cells. The cell membranes o f the embryos contain a protein of approximately 145 kD that is immuno logically related to the mammalian multidrug transport protein and tha t can be cross-linked by a photoactivatable substrate of the mammalian multidrug transport protein. The sediments in which the worm lives co ntain potential substrates for the transporter, indicating that this m ultixenobiotic transport activity may protect Urechis embryos from nat urally occurring toxic compounds. Embryos of a sea urchin from a prist ine environment do not have this transport activity and are sensitive to hydrophobic toxins. These data strongly support a role for multixen obiotic transport as a mechanism of protection from environmental toxi ns and indicate an unsuspected mode of protection in invertebrate embr yos.