Activation of 'immediate-early' genes by estrogen is not sufficient to achieve stimulation of DNA synthesis in rat uterus |
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Authors: | E Persico M Scalona L Cicatiello V Sica F Bresciani A Weisz |
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Institution: | Istituto di Patologia Generale e Oncologia, Prima Facoltà di Medicina e Chirurgia, Università di Napoli, Italy. |
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Abstract: | 17 beta-estradiol, a long acting estrogen that is mitogenic for rat uterus in vivo, or the short acting estrogens estriol and 16 alpha-estradiol, not mitogenic on their own, were injected into adult, castrated rats and their effect on uterine gene expression and rate of DNA synthesis were compared. All three compounds increased steady-state mRNA concentration of c-fos, c-jun and c-myc proto-oncogenes to comparable levels (2 hrs after treatment), whereas only 17 beta-estradiol was found to stimulate significantly DNA synthesis (20-22 hrs later). Based on the different retention time of the tested estrogens in rat tissues, it is concluded that a short exposure to the hormone is sufficient to render uterine cells competent to progress through the cell cycle, via activation of 'immediate-early' genes expression, but that stimulation of DNA synthesis requires further changes, achieved via a prolonged exposure of the cells to the estrogenic stimulus. |
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