Testing chemicals for fish acute toxicity is a legal requirement in many countries as part of environmental risk assessment. To reduce the numbers of fish used, substantial efforts have been focussed on alternative approaches. Prominently, the cell viability assay with the rainbow trout (<em>Oncorhynchus mykiss</em>) gill cell line, RTgill-W1, has been recognized, owing to its high predictive power and robustness. Like gills, the intestine is considered a major site of chemical uptake and biotransformation but, in contrast to gills, is expected to be exposed to rather hydrophobic chemicals, which enter the fish <em>via</em> food. In the present study, we therefore aimed to extend the cell bioassay to the rainbow trout epithelial cell line from intestine, RTgutGC. Using 16 hydrophobic and volatile chemicals from the fragrance palette, we showed that also the RTgutGC cell line can be used to predict fish acute toxicity of chemicals and yields intra-laboratory variability in line with other bioassays. By comparing the RTgutGC toxicity to a study employing the RTgill-W1 assay on the same group of chemicals, a fragrance specific relationship was established which reflects an almost perfect 1:1 relationship between <em>in vitro</em> and <em>in vivo</em> toxicity results. Thus, both cell lines can be used to predict fish acute toxicity, either by using the obtained <em>in vivo-in vitro</em> relationship or by taking the <em>in vitro</em> results at face value. We moreover demonstrate the derivation of non-toxic concentrations for downstream applications which rely on a healthy cell state, such as the assessment of biotransformation or chemical transfer.

Eine umweltrelevante Mischung aus fünf Pflanzenschutzmitteln (PSM) hatte direkte sowie langfristige subletale Effekte auf den Energiehaushalt von jungen Bachforellen. Zudem gab es Wechselwirkungen mit den beiden anderen Stressoren, erhöhter Wassertemperatur und PKD-Parasitenbefall. Die Studie konnte darüber hinaus einen Satz von molekularen Biomarkern identifizieren, die deutlich auf die PSM-Expositionen reagiert haben.