Ingrid Beate Øpstad Fredriksen, from Bergen, studied the effects of pharmaceuticals in wastewater treatment plant (WWTP) effluents using cytotoxicity and luciferase reporter gene assays employing nuclear receptors from cod and zebrafish. Her thesis, entitled “Using ligand-activated receptors from Atlantic cod (Gadus morhua) and zebrafish (Danio rerio) to assess biological effects of pharmaceuticals in wastewater in Bergen, Norway”, demonstrated the ability of WWTPs to remove cytotoxic compounds from the wastewater, but at the same time, many WWTPs released more bioactive compounds (detected by luciferase assays) in the effluents than was present in the influent wastewaters. This observation is probably due to the unmasking of active groups in the pharmaceuticals during biological treatment. The results showed that WWTPs are important for removing cytotoxic compounds in wastewaters, but that their design is important in unmasking biological activity, and that these properties may be monitored using reporter assays based on fish receptors.
The thesis of Anders Vandeskog Borge, also from Bergen, had the title: “Identification and characterization of retinoid X receptors (RXR) in Atlantic cod (Gadus morhua) and their response to organic tin exposure”. In this work he characterized the tissue expression and ligand-binding properties of RXR isoforms from Atlantic cod, based on a luciferase reporter assay that he established during his thesis. Here he showed that whereas RXRgamma was strongly activated by several organotin compounds, RXRbeta1 was not. This was inferred to be due to either or both of an amino acid substitution in Helix 3, or a 14 amino acid insertion in Helix 7, in the RXRbeta1 primary sequence. The findings may be useful in developing a bioassay for organotin contamination, still a problem in hotspots such as old shipyards around the world, although the compounds were banned globally from use as antifoulants on ship hulls in 2003.