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KMID : 0613820090190050593
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Journal of Life Science
2009 Volume.19 No. 5 p.593 ~ p.597
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The Effect of Estrogen on the Transcription of the Insulin-like Growth Factor-I Gene in the Uterus
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Kwak In-Seok
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Abstract
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The uterus plays a critical role in pregnancy and steroid hormones, and both estrogen (E2) and progesterone (P4) especially play important roles in the cross-talk between embryos and uterus to support the pregnancy. E2 stimulates uterine growth during early pregnancy to prepare for implantation of embryos. This cross-talk during the implantation period involves hormones (E2 and P4) and growth factors, including insulin-like growth factor-I (IGF-I). In the uterus of a pregnant pig, the action of E2 is mediated by estrogen receptor-α (ER-α). The expression of ER-a was much higher in early pregnancy than in mid- and late- pregnancy, suggesting E2 secretion from embryos enhances transcription of ER-a during early pregnancy. In order to prove whether IGF-I is an E2 target gene, quantitative real-time PCR was performed on ovariectomized murine uterus with E2 and/or P4 treatment(s). Increased IGF-I mRNA expression was observed with E2 treatment, however, it was not significantly induced by P4 treatment, which clearly demonstrates that, in mice, E2 depends on the activation of uterine IGF-I gene expression. The expression of IGF-I in the uterus of pigs was much higher in early pregnancy than in mid- and late- pregnancy and these data exhibited the same expression pattern with the ER-α gene expression in the uterus. It suggests that a positive co-relationship between IGF-I and ER-α expression exists in the uterus, and that both gene expressions of IGF-I and ER-α are regulated by E2. It further suggests that uterine the IGF-I gene expression might be initiated by E2 secreted from embryos to increase ER-α gene expression, and that this increased ER-α further stimulates the expression of IGF-I in the uterus during early pregnancy.
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KEYWORD
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Estrogen, estrogen receptor-α, insulin-like growth factor-I, progesterone, uterus
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