T3 PM Aquatic Ecotoxicology (Part 2)
Tuesday, 15 November 2005: 1:50 PM - 5:30 PM in Ballroom 3

(LIU-1117-743763) Sodium arsenate enhances thyrotoxicity of sodium perchlorate in zebrafish Danio rerio.

Liu, F-J¹, Wang, J-S¹, Hooper, M¹, Cobb, G¹, Collie, N², Theodorakis, C¹, ¹ TIEHH, Texas Tech University, Lubbock, TX, US² Biology Department, Texas Tech University, Lubbock, TX, US

ABSTRACT- Both perchlorate and arsenic are contaminants in water ecosystem and tightly regulated. These two anions were found to co-exist in aquatic systems. Perchlorate is a thyroid disruptor acting as an inhibitor of iodide uptake into thyroid gland. Thyroid histopathology is widely used as endpoint in evaluating the damage by perchlorate and monitoring the perchlorate contamination. It was hypothesized that arsenic disrupts the homeostasis of deiodinase, which is responsible for the transformation from T4 to T3 thyroid hormone, as can be manifested in thyroid histopathological responses. In order to evaluate their effects on thyroid function and possible interaction between them in terms of histopathology, zebrafish Danio rerio were exposed to sodium perchlorate (10 and 100 ppm), sodium arsenate (1 and 10 ppm), and the mixture-sodium perchlorate + sodium arsenate (10+1 and 100 +10 ppm) plus control for 90 days with triplicates. At day 10, 30, 60, and 90, fish were sampled and processed for histology analysis. Epithelial cell height and colloid area were used as endpoints. Sodium perchlorate exposure resulted in apparent hypertrophy with 100 ppm more effective. However, 1 ppm sodium arsenate showed higher epithelial cell height than 10 ppm, and both concentrations caused hypertrophy. Interaction between these two anions resulted in more pronounced hypertrophy. Colloid depletion (decreased colloid area) was observed at day 10 in all treatments, but over time a compensatory response occurred in fish resulting in partial reversal of colloid depletion. A delay of a compensatory response was observed in the arsenate exposure compared with the perchlorate exposure. Due to the interaction between these two anions, the compensatory response was not observed in the mixture. Further work on other endpoints will give more clues about their effects and interaction.

Key words: sodium arsenate thyroid, sodium perchlorate, thyroid, zebrafish