K C Fertuck1, J Eckel2, C Gennings2 and T R Zacharewski1. 1 Department of Biochemistry and National Food Safety and Toxicology Center, Michigan State University, East Lansing, MI, USA; 2 Department of Biostatistics, Virginia Commonwealth University, Richmond, VA, USA.

Estrogens are classically defined as compounds that are capable of inducing a trophic effect on the uterus. This physiological change has been linked to alterations in the expression of estrogen-responsive genes, but the cascade of molecular events remains unknown. In the present study, the effects of ethynyl estradiol (EE), a synthetic estrogen, on global gene expression in then uterus were examined in immature, ovariectomized C57BL/6 mice. Mice were gavaged with 0.1mg/kg EE or vehicle, and uteri harvested at 0, 2, 8, 12, or 24 hr. Overall, while no differences in uterine weight were found between treatment groups (p=0.296) from 0 to 24 hrs, changes in global gene expression levels were observed during this period. Mu11KsubA Affymetrix GeneChips were used to assess relative expression levels of over 6000 genes in uterine tissue of two animals from each treatment and time-matched vehicle treated (control) group. Data were then screened using standardized t scores to identify gene expression changes outside the normal range of variation for the control group. Treated values were standardized using i) a global control mean and standard deviation assuming no time effect among the control observations, or ii) the average and standard deviation of the time-matched control values. These methods were found to give different results, with the time-matched control approach resulting in the identification of fewer active genes. Large t scores were interpreted to indicate active gene responses. Overall the 24 hr time point had the largest t scores as determined by average ranks and summary statistics over time. The nature of the changes over time was characterized using a parametric model based on the general shape of the time-effect relationship.