Induction of labor with RU 486 (mifepristone) in relaxin-deficient rats: antepartum administration of relaxin facilitates delivery and increases pup survival. 2004

Shuangping Zhao, and O David Sherwood
Department of Molecular and Integrative Physiology, University of Illinois at Urbana-Champaign Urbana, 61801, USA.

OBJECTIVE This study was conducted to determine whether antepartum administration of relaxin improves RU 486-induced delivery at term in rats that lack circulating endogenous relaxin. METHODS Pregnant rats were modified two ways to obtain circulating levels of relaxin and progesterone that resemble those of pregnant humans: relaxin was immunoneutralized throughout the second half of the 23-day pregnancy and high progesterone levels were sustained until term by inserting progesterone implants on day 20. Porcine relaxin was administered subcutaneously from 8 AM on day 20 until delivery. Labor was induced by administering RU 486 subcutaneously at 4 AM on day 22. RESULTS After induction of labor with RU 486, labor and delivery were faster, and the incidence of live births was higher when rats were also administered relaxin during the antepartum period. CONCLUSIONS Antepartum administration of relaxin in combination with RU 486 has beneficial effects on delivery in relaxin-deficient rats.

UI MeSH Term Description Entries
D007279 Injections, Subcutaneous Forceful administration under the skin of liquid medication, nutrient, or other fluid through a hollow needle piercing the skin. Subcutaneous Injections,Injection, Subcutaneous,Subcutaneous Injection
D007743 Labor, Obstetric The repetitive uterine contraction during childbirth which is associated with the progressive dilation of the uterine cervix (CERVIX UTERI). Successful labor results in the expulsion of the FETUS and PLACENTA. Obstetric labor can be spontaneous or induced (LABOR, INDUCED). Obstetric Labor
D007751 Labor, Induced Artificially induced UTERINE CONTRACTION. Induced Labor,Induction of Labor,Labor Induced,Labor Induction,Induced, Labor,Induction, Labor,Inductions, Labor,Labor Inductions
D011247 Pregnancy The status during which female mammals carry their developing young (EMBRYOS or FETUSES) in utero before birth, beginning from FERTILIZATION to BIRTH. Gestation,Pregnancies
D011256 Pregnancy Outcome Results of conception and ensuing pregnancy, including LIVE BIRTH; STILLBIRTH; or SPONTANEOUS ABORTION. The outcome may follow natural or artificial insemination or any of the various ASSISTED REPRODUCTIVE TECHNIQUES, such as EMBRYO TRANSFER or FERTILIZATION IN VITRO. Outcome, Pregnancy,Outcomes, Pregnancy,Pregnancy Outcomes
D012065 Relaxin A water-soluble polypeptide (molecular weight approximately 8,000) extractable from the corpus luteum of pregnancy. It produces relaxation of the pubic symphysis and dilation of the uterine cervix in certain animal species. Its role in the human pregnant female is uncertain. (Dorland, 28th ed) Relaxin B
D001723 Birth Rate The number of births in a given population per year or other unit of time. Natality,Age-Specific Birth Rate,Age-Specific Fertility Rate,Fertility Rate,Age Specific Birth Rate,Age Specific Fertility Rate,Age-Specific Birth Rates,Age-Specific Fertility Rates,Birth Rate, Age-Specific,Birth Rates,Fertility Rate, Age-Specific,Fertility Rates,Natalities,Rate, Age-Specific Fertility,Rate, Birth,Rate, Fertility
D004357 Drug Synergism The action of a drug in promoting or enhancing the effectiveness of another drug. Drug Potentiation,Drug Augmentation,Augmentation, Drug,Augmentations, Drug,Drug Augmentations,Drug Potentiations,Drug Synergisms,Potentiation, Drug,Potentiations, Drug,Synergism, Drug,Synergisms, Drug
D005260 Female Females
D006727 Hormone Antagonists Chemical substances which inhibit the function of the endocrine glands, the biosynthesis of their secreted hormones, or the action of hormones upon their specific sites. Antagonists, Hormone

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