AN IN-VITRO RAINBOW-TROUT CELL BIOASSAY FOR ARYL-HYDROCARBON RECEPTOR-MEDIATED TOXINS

Halogenated aromatic hydrocarbons (HAHs) and other chemicals that act as aryl hydrocarbon (Ah) receptor (AhR) agonists cause a variety of to xic effects. In sac fry of many fish species, these effects include bl ue-sac disease and mortality. Because HAHs occur in complex mixtures, their toxicity in the environment is difficult to predict. A bioassay useful in predicting AhR-mediated toxicity to fish was developed using the RTH-149 rainbow trout hepatoma cell line. Stable transfection of this cell line with the pGudLuc 1.1 plasmid, which contains a firefly luciferase reporter gene under the transcriptional regulation of dioxi n responsive enhancers, has produced a recombinant cell line designate d Remodulated Lightning Trout (RLT 2.0). The RLT 2.0 bioassay method d etection limit for 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is 4 pM. The responses of the RLT 2.0 bioassay to TCDD and several HAH congene rs closely matched the responses observed in vivo in fish. The RLT 2.0 bioassay can provide an integrative measure of the total AhR-mediated toxic activity of complex mixtures to fish. The assay will be useful in screening environmental extracts, guiding chemical analysis, and in terpreting the AhR-mediated mechanism of toxicity.