Earlier tiers test individual cells and tissue samples for hormonal effects; this tier looks at the whole animal for complex systemic effects.
We recommend using whole animal assays with fish and/or amphibia (frogs). In vivo assays – or live animal tests – allow for the examination of multiple endpoints, for multiple hormones, and multiple mechanisms of action.
Assays using fish (eg. zebrafish and medaka) can cast a wide net to detect multiple potential teratological effects (classical toxicology endpoints, like mutation and death), but can also detect sensitive endocrine-affected endpoints – all of which have relevance for human health.
Because fish assays can detect broad toxicological effects, new compounds can be screened without prior information on suspected activity or expected mechanisms of action. Because these tests can find unexpected systemic effects, the Fish and Amphibian tier is needed for any chemicals that “passed” TiPED’s first three tiers.