Amphibian Metamorphosis Assay (AMA)

An amphibian metamorphosis assay intended to screen substances which may interfere with the normal functioning of the hypothalamo-pituitary-thyroid axis.

The assay is validated with the species Xenopus laevis.

The assay uses three test chemical concentrations and the necessary controls, including a carrier control if necessary. The assay starts with tadpoles at the development stage 51 on the Nieuwkoop and Faber scale and is extended for a duration of 21 days. Four replicate test vessels are used for each treatment level and control(s). After 7 days of exposure, a sub-set of tadpoles from each treatment level is sampled for the measurement of the length of the hind-limb.

At termination of 21-day exposure period, developmental stage, snout-to-vent length and hind limb length are measured on all remaining tadpoles. A sub-set of tadpoles from each treatment level is fixed (whole-body or dissected) for histopathology of the thyroid gland.

Vertebrate, Chronic, Freshwater.

OECD (2009), Test No. 231: Amphibian Metamorphosis Assay, OECD Guidelines for the Testing of Chemicals, Section 2, OECD Publishing, Paris, https://doi.org/10.1787/9789264076242-en.