| Estrogen and progesterone as an important steroid hormone, has an important role in the start of rats pregnancy, maintain placental function, fetal growth and development, and in the onset of labor. Suitable estrogen and progesterone levels are key factors to ensure the continued pregnancy is the most basic conditions.To determine the effect of transient inhibition of estrogen production in vivo in post-implantation period on fetus and plancenta and pregnancy outcome in normal rats.Objective:To determine the effect of transient inhibition of estrogen production in vivo in post-implantation period on pregnancy outcome in normal rats.Methods:Rat embryo implantation GD 6.5 to GD 8.5 administering estrogen inhibitor letrozole orally (experimental group) or vehicle orally (control group), to observe its effects on fetal development and birth outcomes. Results In the control group could normal delivery in GD22.5, pregnant rats at GD 22.5 can not be normal delivery and exhaustion death at GD 23.5, and when caesarean section to remove the fetus at GD 22.5 found both the weight and growth of offspring are normal development, and on behalf of milk can survival; the experimental and control groups of litter size and fetus weight was no significant difference (P> 0.05); experimental group and the control group increased placental weight (P<0.05), and histological abnormalities; GD 21.5 and GD 22.5, the control group in peripheral blood progesterone levels rapidly decreased to 6.7 ± 4.4 nmol/L and 5.6 ± 3.5 nmol/L, progesterone levels in the experimental group were 19.7 ± 7.0 nmol/ L and 18.0 ± 4.2 nmol/L, significantly higher (P<0.05); Conclusion:Rat embryo implantation given letrozole after a brief inhibition of estrogen synthesis can lead to pregnant rats dystocia, placenta morphological abnormalities, while the end of pregnancy progesterone levels can not be quickly decline.The reason of pregnant rats after implantation transient suppression of estrogen synthesis in pregnant rats.Objective:To investigate the possible causes of the above dystocia pregnant rats. The method of rodent required progesterone levels decreased before labor, we measured serum progesterone levels before labor, experimental results suggest that progesterone levels did not decline may be the cause of dystocia. To confirm this we use anti-progesterone mifepristone from blocking progesterone receptor levels in effect was observed on labor. Results:After embryo implantation GD 6.5 to GD 8.5 administered estrogen inhibitor letrozole orally (experimental group) or vehicle orally (control group), two groups of pregnant mice were each in GD 19.5, GD 20.5 and GD 20.5, GD 21.5 consecutive 2 d mifepristone, two groups of pregnant rats were parturition respectively GD 20.5 and GD 21.5 and normal production can not prove the progesterone receptor inactivation experiments letrozole group dystocia reasons. At the same time with the real-time PCR Progesterone observed downstream target of CX43 expression in the uterus of late pregnancy. Lower than the experimental group and control group GD22.5 uterine muscle expression of CX43 (p<0.01), the experimental group using mifepristone group and not use mifepristone GD20.5 uterine muscle CX43 upregulation (p)>0.01); Conclusion:Rat after embryo implantation given letrozole after a brief inhibition of estrogen synthesis in pregnant rats can lead to the end of pregnancy progesterone levels are not decreased rapidly thereby causing dystocia, in late pregnancy mifepristone can save dystocia outcome. |
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