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Non-additive dose dependent gene expression patterns exhibited by a mixture of 17-alpha ethynylestradiol and genistein in vivo. Gupta R1,3, Burgoon, LD2,3, Harney AS1,3, Boverhof, DB1,3, Kwekel, J1,3*, Gennings, C, Zacharewski, TR1,3. 1Dept of Biochemistry & Molecular Biology, 2Dept of Pharmacology & Toxicology, 3Center for Integrative Toxicology, and National Food Safety & Toxicology Center, Michigan State University, East Lansing, MI 48824. Human populations are generally exposed to subthreshold doses of the phytoestrogen genistein, however there are concerns regarding non-additive interactions with other exogenous and endogenous estrogens. Coadministration of submaximal doses of 17-alpha ethynylestradiol (EE) and genistein (GEN) were studied to identify non-additive gene expression interactions. Immature, ovariectomized mice were gavaged with 3, 10, 30, 100, or 300ug/kg EE; 0.3, 0.9, 3, 9, or 30mg/kg GEN; a 1:100 mixture of EE and GEN (same doses as above), or sesame oil vehicle. Animals were sacrificed 24hrs following administration and uterotropic effects and hepatic gene expression was examined. All doses of EE and selected doses (3/0.9; 10/3; 30/9; 100/30 ug/kg / mg/kg) EE/GEN induced uterine wet weight; while GEN failed to elicit a significant (a = 0.05) uterotropic response. Custom cDNA microarrays with 13,824 features representing 8661 unique genes were used to monitor changes in hepatic gene expression from EE, GEN, or mixture treated mice. EE and mixture samples clustered together, while GEN samples clustered separately. Eighty genes exhibited a monotonic response in either EE or GEN treated hepatic samples. Of these, 23 exhibited non-additive interactions as assessed by the single chemical required (SCR) method. Gene functions represented by these 23 genes included steroid metabolism and biosynthesis and response to oxidative species, and are localized to the endoplasmic reticulum and the mitochondria. Results from these studies demonstrate non-additive interactions between EE and GEN that warrant further investigation. Supported by NIH Grants R01 ES11271 and *T32 ES07255. |
