An evolutionary test of the isoform switching hypothesis of functional progesterone withdrawal for parturition: humans have a weaker repressive effect of PR-A than mice
Abstract
Background: A decrease in maternal serum progesterone (P4) concentrations precedes the onset of labor in most placental mammals. Humans differ by maintaining high levels of P4 throughout birth. Parturition in humans probably includes mechanisms that undercut the pregnancy sustaining function of P4. One attractive hypothesis is the isoform switching hypothesis (ISH). ISH is supported by in vitro evidence that progesterone receptor isoform A (PR-A) inhibits PR-B and that the PR-A/PR-B ratio increases towards term.
Materials and methods: Here, we test the hypothesis that isoform switching is an adaptation to high levels of P4 at term, predicting that, in humans, PR-A mediated repression of PR-B is stronger than in mouse. We use reporter assays with human and mouse PRs to detect species differences in the repressive effects of PR-A.
Results: We found that human PR-B is less sensitive to repression by human PR-A than mouse PR-B, contrary to our prediction. The difference between human and mouse PR-B sensitivity is most pronounced at PR-A/PR-B ratios typical for the preterm myometrium.
Conclusions: Our results are inconsistent with the ISH. We speculate that, instead, the lower sensitivity of human PR-B to PR-A may be relevant for the maintenance of pregnancy at high progesterone levels and increasing PR-A concentrations towards term.
©2012 by Walter de Gruyter Berlin Boston
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Articles in the same Issue
- Masthead
- Masthead
- Review Article
- Noninvasive prenatal diagnosis of Down syndrome: current knowledge and novel insights
- Original Articles – Obstetrics
- Midtrimester amniotic fluid concentrations of interleukin-6 and interferon-gamma-inducible protein-10: evidence for heterogeneity of intra-amniotic inflammation and associations with spontaneous early (<32 weeks) and late (>32 weeks) preterm delivery
- An evolutionary test of the isoform switching hypothesis of functional progesterone withdrawal for parturition: humans have a weaker repressive effect of PR-A than mice
- Fetomaternal hemorrhage in the second trimester
- Contribution of 3D power Doppler ultrasound to the evaluation of placental circulation in normal pregnancies and pregnancies complicated by preeclampsia
- Two vs. three or more primary recurrent pregnancy losses – are there any differences in epidemiologic characteristics and index pregnancy outcome?
- Oxidative stress stimulates α-tocopherol transfer protein in human trophoblast tumor cells BeWo
- Risk factors for preeclampsia in twin pregnancies: a population-based matched case-control study
- Bishop score and cervical length at 33–35 weeks of gestation and the risk of intrapartum cesarean delivery of twins
- Primary vs. secondary recurrent pregnancy loss – epidemiological characteristics, etiology, and next pregnancy outcome
- Safety and efficacy of high-dose intravenous iron carboxymaltose vs. iron sucrose for treatment of postpartum anemia
- Knowledge gap of recommendations in ACOG practice bulletins: A survey of members of the Central Association of Obstetricians and Gynecologists
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- Three years’ experience of using a 29-gauge atraumatic needle for amniocentesis
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- Acquisition of full enteral feeds may depend on stooling pattern in very premature infants
- An open-label, randomized efficacy and safety trial of subcutaneous and intramuscular BT088 (Fovepta) human hepatitis B immunoglobulin in neonates of HBV-carrier mothers
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