In vitro Bioassays - Valuable Tools Contributing to the Conservation of Endangered Species

Exposure assessment usually is performed by means of chemical analytical methods and subsequently reporting the concentration of known and expected pollutants. Effects assessment typically measure the effects of single compounds or mixtures on laboratory experimental animals. Because these compounds often are present in complex mixtures, the difficulties and costs for chemical analysis to assess internal exposure in organisms are rapidly increasing. More importantly, chemical analysis alone often is not sufficient for toxicological risk assessment because mixture effects cannot yet be predicted and unknown compounds and biotransformation products may contribute significantly to the toxicological risk. An alternative approach is to detect and quantify the presence of endocrine disrupting chemicals by means of biological markers to assess exposure and effect. During recent years a range of in vitro bioassays have been developed, validated, and applied that are able to detect compounds having a "common mechanism of action." Biological test systems based on a "common mechanism of action" may provide very useful and rapid screening methods by measuring the biological potency of single compounds, mixtures or environmental extracts, with outcomes identifying the effects of hitherto unknown and eventually species-specific metabolites of the compounds in question. Reporter gene assays, also have been used in many studies and the combination of speed, relative simplicity, and ability to integrate effects of complex mixtures also makes it a valuable additional tool for studies related to pollution in endangered species such as otters and their environment.