Researchers have discovered a protein, which transports chemicals out of zebrafish embryos thereby protecting the embryos against toxic substances. However, certain environmental chemicals render this protective mechanism ineffective, so that the fish embryos become more sensitive to toxic substances. The study, published in the scientific journal BMC Biology, could prove to be of great importance for the future assessment of chemicals.
Fish possess a number of different mechanisms for protection against harmful substances in an aquatic environment. These include molecular transport systems, such as the so called ABC transporters, which prevent the penetration of toxic substances into cells. ABC transporters have been well investigated for mammals. For fish and their embryos, however, little is known about such transporters.
Dr Till Luckenbach (Helmholtz Centre for Environmental Research, or UFZ) and Dr Stephan Fischer (Swiss Eawag aquatic research institute, or Eawag) together with other colleagues have now found that the transport protein Abcb4 actively extrudes chemicals from the embryo of the zebrafish.
In follow-on investigations the researchers measured the activity of the transport system, enabling the identification of the chemicals that Abcb4 transports. However, certain substances block the transport mechanism. This inhibition renders its function ineffective, and other harmful substances can penetrate into the organism. “Compounds which inhibit the transporter throw open the doorway for other toxic substances “, says Fischer.” These are also referred to as chemosensitisers, as they make the organism more sensitive to harmful chemicals. This indirect toxic effect plays an important role, above all in mixtures of substances such as frequently found in our environment.”
“Zebrafish embryos are used for the assessment of chemicals and for investigations of environmental impact, so we hope that in future our study will contribute to an awareness of the need to incorporate Abcb4 transport processes in toxicological testing directives,” said Luckenbach.