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CHANGES IN EXPRESSION OF PHOSPHORYLATED AND TOTAL ERK 1/2 IN TCDD-EXPOSED EMBRYONIC MOUSE PALATES
Citation:
Wolf, C J. AND B D. Abbott. CHANGES IN EXPRESSION OF PHOSPHORYLATED AND TOTAL ERK 1/2 IN TCDD-EXPOSED EMBRYONIC MOUSE PALATES. Presented at Society of Toxicology, New Orleans, LA, March 6-10, 2005.
Description:
CHANGES IN EXPRESSION OF PHOSPHORYLATED AND TOTAL ERK1/2 IN TCDD-EXPOSED EMBRYONIC MOUSE PALATES.
C Wolf and B Abbott, USEPA, ORD, NHEERL, Reproductive Toxicology Division, Research Triangle Park, NC 27711
2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) induces cleft palate in mice by preventing fusion of the palatal shelves. TCDD maintains EGF and EGF receptor (EGFR) expression levels in the medial epithelial cells of the palate at a time when EGFR levels fall in those of controls.EGFRactivates the MAPK ?ERKpathway; therefore,MAPK signaling may play a critical role in mediating TCDD-induced cleft palate. In this study, we examined whetherTCDD exposure alters MAPK signaling by monitoring the ratio of phosphorylated ERK (pERK) to total ERK (tERK) inembryonic mouse palates. Pregnant mice were dosed with 24 ug/kg TCDD or corn oil (control, CO) on gestational day (GD)12 and embryos were collected on GD 14. Embryonic palates from 5 control and 5 treated litters were isolated and pooled by litter.pERK andtERK proteinswere quantitated by densitometric analysis of Western blots and by ELISA, and the ratio of pERK/tERK was determined. On Western blots, all bands were normalized to beta-actin, and ERK appeared as 2 bands, ERK1 and ERK2. Western analysis revealed that thepERK/tERK ratio wasreducedin the TCDD (0.25 ? 0.05) compared to CO (0.41 ? 0.08; p< 0.01) groupfor ERK1 but not for ERK2(0.25 ? 0.09 TCDD vs. 0.33 ? 0.10CO). There was more tERK1in the TCDD group than in the CO group. ELISA analysis showed the ratio of pERK/tERK was not different in the TCDD compared to the CO groups. However, ELISA analysis does not separate ERKs 1 and 2 and may not be able to detect changes in one isoform. When data from both bands were added together in the Western analysis, no significant difference was found in the ratio of pERK/tERK ratio between TCDD and CO groups. These preliminary resultssuggesttERK1 is more abundant but kinase activity is not increased to maintain the ratio of pERK/tERK in palates exposed to TCDD. Additional data on pERK/tERK at other time points and in specific areas of the palate may more fully illustrate the pathway for TCDD-induced cleft palate. [This abstract does not necessarily reflect EPA policy].