Experiences in developing the Amphibian Metamorphosis Assay for regulatory testing – a CRO perspective.

Severine Larroze, Deanna Westfold, Richard Maunder

To support global chemical risk assessments for our clients, we have established and maintained a female Xenopus laevis colony and investigated the feasibility of amphibian testing at our laboratory at Scymaris Ltd. Frogs are housed in groups of 6 individuals and spawned every three months on rotation to ensure good egg production and the capacity to start studies monthly.

The test was conducted at Scymaris, Brixham laboratory, UK.

The Amphibian Metamorphosis Assay (AMA; Ref 1) is a conceptual framework level 3 screening assay to identify substances interfering with the hypothalamic-pituitary-thyroid (HPT) axis. Amphibian metamorphosis is modulated via thyroid dependent processes and X. laevis is a well-studied and easy to keep under laboratory conditions amphibian model. The observational endpoints for this assay are Hind Limb Length (HLL), Snout to Vent Length (SVL), developmental stage, wet weight, thyroid histology and mortality.