Assessment of Protocol Designed to Detect Endocine Disrupting Effects of Flutamide in Xenopus Tropicalis

Abstract : This technical report represents a pilot study to test a new protocol with an amphibian frog species, Xenopus tropicalis, for possible application in the U.S. Environmental Protection Agency (USEPA) Endocrine Disruptor Screening and Testing Program. The frogs were exposed to the model anti-androgenic compound flutamine under flow-through conditions for a period of 30 weeks, beginning at 48 hours post-hatch. The endpoints evaluated for this study were (1) overall health of the frogs, w) body lengths and weights, (3) weights of liver and ovary/egg masses, (4) histopathology of gonads, and (5) plasma vitellogenin levels. Although considerable variability was encountered in the results, statistically significant differences in most endpoints were detected among frogs with different exposure concentrations to flutamide. The authors concluded that development of a X. tropicalis bioassay to screen chemicals for endocrine disruption in amphibians is feasible. Recommendations include: (1) Modification of the test design, (2) Development of additional endpoints, and (3) Careful selection of test chemicals for bioassay development.