PH25 Wildlife Ecotoxicology II
Exhibit Hall
8:00 AM - Thursday
(PH284) Aromatase enzyme as an endpoint for embryonic exposure to methyoxychlor in Japanese quail (Coturnix japonica).
McKernan, M1, Abdelnabi, M1, Hazelton, J1, Quinn, M1, Thompson, N1, Ottinger, M1, 1 University of Maryland, College Park, MD, USA
ABSTRACT- The aromatase enzyme, which metabolizes androgen to E2, is an important element in the process of sexual differentiation and critical to sexual behavior in adult male quail. Aromatase activity in the brain, specifically in the preoptic area, is sexually dimorphic and steroid hormone responsive in Japanese quail (Coturnix japonica). Therefore, aromatase may be a useful indicator of exposure to endocrine disruption during sexual differentiation, especially in areas of the brain that are important for mediating reproductive behavior and neuroendocrine response. A two-generation dietary study was conducted to determine the effects of endocrine disrupting chemicals (EDCs) on avian species. Japanese quail (parents; P) were raised under short photoperiod and then photostimulated and placed on diet containing methoxychlor (0, 5ppm, and 10ppm), which is a commonly used pesticide with known estrogenic effects. Chicks (F1) were raised on the same diet as their parents, paired as adults, and monitored for sexual maturation, reproductive behavior and endocrine measures. The F1 chicks are exposed during embryonic development and via the diet. Therefore, we examined aromatase activity in F1 hatchlings. F1 hatchlings (N = 29) were sampled and aromatase activity was measured in the microdissected preoptic region of the brain. Activity was quantified in each brain by measuring the release of tritiated water during aromatization of [1
-3H]androstenedione. There was a trend of greater activity in hatchlings, specifically 11.05 ± 1.44, 21.44 ± 4.22, and 36.52 ± 9.89 fmol/hr/mg protein in controls, 5ppm, and 10ppm respectively. We noticed an almost bimodal distribution in response suggesting that high variability is an important factor in evaluating aromatase activity. These data indicate that aromatase activity may be an important endpoint to consider when evaluating the effects of endocrine disruption. Supported by EPA R-82877801.
Key words: aromatase enzyme, endocrine disrupting chemicals, japanese quail, methoxychlor