PARENT SESSION

PM10 Mechanisms of Toxic Action
Exhibit Hall
8:00 AM - Monday

(PM161) Relationship between brain and ovary aromatase activity in the fathead minnow.

Villeneuve, D¹, Knoebl, I², Kahl, M¹, Jensen, K¹, Hammermeister, D¹, Ankley, G¹, ¹ US EPA Mid-Continent Ecology Divison, Duluth, MN, USA² US EPA Ecological Exposure Research Division, Cincinnati, OH, USA

ABSTRACT- There is growing evidence that some chemicals present in the environment have the capacity to inhibit or potentially induce aromatase activity. As a result, measures of aromatase activity in brain and/or ovary tissue may be useful as an optional diagnostic endpoint for use with the short-term fathead minnow (FHM) endocrine disruptor screening assay. This study compared aromatase activities in brain and ovary tissue from non-exposed FHM representing different ages and stages of reproductive development and from FHM exposed to the aromatase inhibitor fadrozole for 7 d. Exposure to 1.85 and 5.5 g/L fadrozole increased ovary aromatase activity relative to controls. Brain aromatase activity was unaffected. At greater concentrations, 16.7 and 50 g/L, brain aromatase activity was inhibited relative to controls, while ovary activity was unaffected. Aromatase activities measured in brain and ovary tissues from the same fish were not strongly correlated for either fadrozole exposed (R²=0.020) or control fish (R² = -0.421). Overall, the results suggest that in FHM, ovary and brain aromatase activity are regulated differently. Tissue-dependent differences in concentration-response relationships, time-courses, and in vivo sensitivity to various aromatase inhibitors/inducers appear likely. Greater understanding of the regulation of aromatase activities in one or both tissues may be needed to reliably define mechanism of action and predict effects based on measures of aromatase activity.

Key words: mechanism of action, endocrine disruption, aromatase, fadrozole