Fish cell lines as versatile tools in ecotoxicology: assessment of cytotoxicity, cytochrome P4501A induction potential and estrogenic activity of chemicals and environmental samples.

In vitro systems such as primary cells and cell lines are of growing importance in ecotoxicology. Cells from different tissues and species of fish are used for the assessment of toxic action of chemicals and evaluation of environmental samples. For organotins and substituted phenols, we have found that the in vitro cytotoxicity is positively correlated with the acute toxicity in vivo, and therefore cytotoxicity assays may serve as an alternative for acute fish toxicity testing. We have been using the hepatocellular carcinoma (PLHC-1) cell line for the assessment of the cytochrome P4501A (CYP1A) induction potential of polyaromatic hydrocarbons (PAHs), nitro-PAHs and azaarenes. For these compounds, the CYP1A induction potential is found to be related to the molecular structure and lipophilicity. In mixtures, CYP1A induction of individual compounds is additive. Based on the comparative investigation of the induction potential we derived an induction equivalency (IEQ) concept that can be applied for the evaluation of environmental samples such as landfill leachates, sediments and motorway runoffs. Fish cell lines are also valuable, rapid and cost-effective tools for the assessment of estrogenic activity of chemicals and environmental samples. We have developed an estrogen-responsive reporter gene system using the rainbow trout gonad cell line RTG-2, in which an estrogen receptor beta form is expressed at very low levels, but is not inducible. As the estrogenic activity is dependent on the cellular level of estrogen receptor (ER), ER has to be co-transfected in transient transfections in addition to an estrogen-responsive reporter gene. Using a dual luciferase system, the estrogenic activity of 12 compounds including alkylphenols, DDT-isomers and its metabolites have been assessed. Our system shows a high sensitivity with a detection limit of 0.05 nM estradiol and is therefore more sensitive than many other mammalian or yeast systems. The relative estrogenic activity (e.g. o,p'-DDT) and other toxicological effects may differ from those in mammalian systems, indicating that a risk evaluation for fish could only be meaningfully assessed in fish-specific systems. This paper illustrates the versatility and high potential of fish cell lines in ecotoxicology.