Inefficacy of dietary test substance administration in Amphibian Metamorphosis Assay (AMA) studies

AbstractTraditionally, the Amphibian Metamorphosis Assay (AMA; OECD TG 231) is performed by exposingXenopus laevis tadpoles to test substances dissolved in laboratory water. Recently, the use of dietary administration has been proposed to combat poorly soluble test substances in ecotoxicologically-based regulatory endocrine disruption (ED) studies, specifically the AMA warranting an investigation into the efficacy of dietary administration. An efficacy study comprised of two phases: 1) evaluation of the physical influence of the loading process via solvent and 10, 1, and 0.1  mg/l test substance or surrogate (sunflower oil, SFO) on the Sera® Micron Nature (SMN) diet, and 2) performance of a modified AMA in which Nieuwkoop and Faber (NF) stage 51X. laevis larvae were exposed to dechlorinated tap water using one concentration of the SFO in the diet for 21  days, was performed. In phase 1, the addition of acetone or acetone with bis(2-propylheptyl) phthalate (DPHP) or SFO to SMN with subsequent solvent purge altered the diet reducing the density of the liquified diet and dietary pellet size following centrifugation indicative of alteration of the ph ysical properties of the diet. Treatments used in the modified AMA were acetone alone and 0.1 mg/l SFO dissolved in acetone. These treatments were evaluated against an SMN benchmark using standard AMA endpoints. Both the acetone-treated SMN and 0.1 mg/l SFO-treated diets significantly reduced su rvival rates, 67 and 70% rela...
Source: Journal of Applied Toxicology - Category: Toxicology Authors: Tags: RESEARCH ARTICLE Source Type: research