Progesterone “block”

Csapo, A.I.

doi:10.1002/aja.1000980206

Cited by 352 publications

(161 citation statements)

References 17 publications

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“…These physiological changes occurred before the time when the conceptus was firmly attached to the caruncular epithelium (Boshier, 1969), though recent studies indicate that trophectoderm papillae have already protruded into intercaruncular glandular openings by Day 15 post coitum (Guillomot, Fléchon & Wintenberger-Torrès, 1981;Wooding, Staples & Peacock, 1981). The inhibition of spontaneous myometrial activity in this peri-implantation period resembled the classic progesterone 'block' described by Csapo (1956Csapo ( , 1977 . Greiss & Anderson (1970a) Ford, Chenault & Echternkamp, 1979; pigs: Ford & Christenson, 1979), particularly in the uterine horn occupied by a conceptus, and these increases have been correlated with oestrogen production by the early embryo.…”

Section: Discussionmentioning

confidence: 77%

Uterine blood flow, myometrial activity and their response to adenosine during the peri-implantation period in sheep

Fleet¹,

Heap²

1982

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Summary. Uterine blood flow and myometrial activity were measured simultaneously in anaesthetized sheep 15 days after a sterile (non-pregnant group) or fertile (pregnant) mating. During the peri-implantation period uterine blood flow was similar in both groups of animals, but spontaneous myometrial activity was greatly reduced in pregnant ewes. This 'block' of myometrial activity was associated with circulating levels of progesterone which were significantly higher (2\m=.\8\ m=+-\0\m=.\8ng/ml, mean \m=+-\ s.e.m.) than those in non-pregnant animals (0\m=.\4 \m=+-\0\m=.\3 ng/ml). Adenosine injected into the uterine artery produced uterine vasodilatation in both groups, but the log dose\p=n-\response was significantly less in pregnant than in non-pregnant animals (P < 0\m=.\001).Myometrial activity was stimulated by adenosine, particularly in the pregnant group (P < 0\m=.\001

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Section: Discussionmentioning

confidence: 77%

Uterine blood flow, myometrial activity and their response to adenosine during the peri-implantation period in sheep

Fleet¹,

Heap²

1982

Reproduction

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“…1 However, the role of progesterone withdrawal, as measured by plasma progesterone concentration or the ratio of progesterone/estrogens, in the initiation of normal labor in humans or other primates is unclear. [2][3][4] Nevertheless, there is evidence that functional progesterone withdrawal caused by changes such as reduction in progesterone receptors 5 or relative increase in the progesterone receptor (PR)-A progesterone receptor isoform, which blocks PR-B isoform-mediated gene transcription 6 may trigger labor in humans.…”

Section: Introductionmentioning

confidence: 99%

Salivary progesterone and estriol among pregnant women treated with 17-α-hydroxyprogesterone caproate or placebo

Klebanoff

Meis

Dombrowski

et al. 2008

American Journal of Obstetrics and Gynecology

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OBJECTIVE-The objectives of the study was to determine whether salivary progesterone (P) or estriol (E3) concentration at 16-20 weeks' gestation predicts preterm birth or the response to 17α-hydroxyprogesterone caproate (17OHPC) and whether 17OHPC treatment affected the trajectory of salivary P and E3 as pregnancy progressed.STUDY DESIGN-This was a secondary analysis of a clinical trial of 17OHPC to prevent preterm birth. Baseline saliva was assayed for P and E3. Weekly salivary samples were obtained from 40 women who received 17OHPC and 40 who received placebo in a multicenter ran-domized trial of 17OHPC to prevent recurrent preterm delivery.RESULTS-Both low and high baseline saliva P and E3 were associated with a slightly increased risk of preterm birth. However, 17OHPC prevented preterm birth comparably, regardless of baseline salivary hormone concentrations. 17OHPC did not alter the trajectory of salivary P over pregnancy, but it significantly blunted the rise in salivary E3 as well as the rise in the E3/P ratio. NIH Public AccessAuthor Manuscript Am J Obstet Gynecol. Author manuscript; available in PMC 2009 December 16. Published in final edited form as: Am J Obstet Gynecol. 2008 November ; 199(5): 506.e1-506.e7. doi:10.1016/j.ajog.2008.003. NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript CONCLUSION-17OHPC flattened the trajectory of E3 in the second half of pregnancy, suggesting that the drug influences the fetoplacental unit. Keywords17-alpha-hydroxyprogesterone caproate; longitudinal studies; preterm birth; salivary estriol; salivary progesterone Progesterone has long been recognized as necessary for pregnancy maintenance, and the role of progesterone withdrawal in the initiation of labor in animal species has been known for decades. 1 However, the role of progesterone withdrawal, as measured by plasma progesterone concentration or the ratio of progesterone/estrogens, in the initiation of normal labor in humans or other primates is unclear. 2-4 Nevertheless, there is evidence that functional progesterone withdrawal caused by changes such as reduction in progesterone receptors 5 or relative increase in the progesterone receptor (PR)-A progesterone receptor isoform, which blocks PR-B isoform-mediated gene transcription 6 may trigger labor in humans. We are unaware of any study that has assessed the ability of measurement of salivary progesterone, which is representative of the biologically active unbound fraction in plasma or serum, 7 to predict preterm birth.In 2 recent randomized clinical trials, injections of 17-α-hydroxyprogesteronecaproate (17OHPC) 8 or vaginal suppositories containing progesterone 9 reduced the recurrence or occurrence of preterm birth among high-risk women. Because 17-α-hydroxyprogesterone is produced by the normal placenta in amounts greater than the doses administered in these clinical trials 10 and because normal plasma progesterone concentrations are 9 times higher than those of 17-α-hydroxyprogesterone 11 and greater than the dissociation c...

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“…Progesterone appears to restrain the activity of the myo¬ metrium during pregnancy (Stys et al, 1978;Kubli-Garfias et al, 1983), and this is the basis of the 'progesterone-block' theory (Csapo, 1956). In this theory, antiprogestin acts as a proges¬ terone receptor antagonist and thereby induces delivery in rats (Chwalisz et al, 1986) and other species including humans (Frydman et al, 1992).…”

Section: Introductionmentioning

confidence: 99%

Length tension relationships in the nonpregnant and pregnant rat uterus and the effect of antiprogestin

Knudsen

Svane²,

Forman³

1998

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Progesterone “block”

Cited by 352 publications

References 17 publications

Uterine blood flow, myometrial activity and their response to adenosine during the peri-implantation period in sheep

Uterine blood flow, myometrial activity and their response to adenosine during the peri-implantation period in sheep

Salivary progesterone and estriol among pregnant women treated with 17-α-hydroxyprogesterone caproate or placebo

Length tension relationships in the nonpregnant and pregnant rat uterus and the effect of antiprogestin

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