21DAY: Phase 3 of the validation of the OECD Fish Screening Assay

Description

The eight studies in the attached report were conducted as part of OECD Test Guideline program to validate a standardized OECD protocol for a 21-day fish screening assay for the detection of endocrine active substances (i.e. estrogen, aromatase inhibitors, androgen). Work in the previous Phases involved 3 fish species and a set of positive and negative compounds. In January of 2006, Cefic volunteered to support additional work with three test substances in the fathead minnow (Pimephales promelas). Other laboratories were invited to participate, and both Denmark and Germany agreed to support studies with octylphenol in the zebrafish (Danio rerio). Given that the database with the third species, medaka (Oryzias latipes) was more extensive (e.g., octylphenol and pentachlorophenol have already been tested by the Ministry of Environment, Japan), the VMG-eco and the EDTA Task Force recognized that further studies were not necessary for the validation with medaka.

The objective was to continue the testing of the relevance and reproducibility of two endocrine-related endpoints: vitellogenin (VTG) and secondary sexual characteristics (SSC). The current studies employed difficult and challenging test substances: a weak estrogen (octylphenol), a weak aromatizable androgen (androstenedione), and a difficult negative test substance (sodium pentachlorophenol).

The results of these studies herein fully support the overall conclusion of the OECD validation program that VTG and SSC can be successfully employed to screen for certain endocrine modes of actions (i.e., estrogens, androgens, and aromatase inhibitors). At concentrations absent of overt signs of toxicity, there were no false positives or negatives observed with any of the three negative test substances directly related to the protocol itself.