Ritodrine: a beta-adrenergic receptor antagonist in human amnion
Article Abstract:
The beta-2-adrenergic agonist ritodrine appears to act as an antagonist in human amnion. Ritodrine is a drug that causes uterine muscle to relax and is used to treat premature labor. It also induces low blood sugar and rapid heart beat in the newborn and mother. In a laboratory experiment, amnion cells were taken from human placentas following delivery and grown on culture. The activity of ritodrine on amnion cells was compared with that of known beta-adrenergic agonists. Unlike the agonists, ritodrine did not stimulate cyclic AMP (cAMP) or prostaglandin E2 production in the cells. Furthermore, it blocked the stimulatory effects of known agonists on cAMP and prostaglandin E2 production. In addition to its effects on uterine muscle, ritodrine may block the release by the amnion of prostaglandins that trigger the onset of labor.
Publication Name: American Journal of Obstetrics and Gynecology
Subject: Health
ISSN: 0002-9378
Year: 1993
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Fetal membranes inhibit prostaglandin but not oxytocin-induced uterine contractions
Article Abstract:
The fetal membranes appear to produce a substance that can inhibit contractions induced by prostaglandin E2 but not contractions induced by oxytocin. Rat uterine muscle strips were suspended in a bath. Prostaglandin E2 or oxytocin was introduced, and the intensity of contractions was recorded for one hour. A piece of fresh human fetal membrane obtained after a term labor was introduced into the chamber for the second hour. The membranes were removed for the third and final hour. The presence of the membranes inhibited contractions by 22% when contractions were induced by prostaglandin E2 but not when contractions were induced by oxytocin. This is additional support for the theory that the fetus plays an important role in initiating labor at the appropriate time.
Publication Name: American Journal of Obstetrics and Gynecology
Subject: Health
ISSN: 0002-9378
Year: 1995
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Human fetal membranes inhibit calcium L-channel activated uterine contractions
Article Abstract:
Fetal membranes, specifically the chorion, may prevent uterine contractions by inhibiting the calcium L-channel of the uterus. Researchers obtained rat fetal membranes and uterine muscles to measure the contractions induced by Bay K 8644, a calcium L-channel agent. Bay K 8644 caused uterine muscle to contract, but its effect was inhibited by full-thickness fetal membranes. The chorion layer of the fetal placenta rather than the maternal layer was responsible for contraction inhibition. The chorion may emit a calcium channel inhibitor to prevent uterine contractions and may screen out contraction-inducing stimulants.
Publication Name: American Journal of Obstetrics and Gynecology
Subject: Health
ISSN: 0002-9378
Year: 1996
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- Abstracts: Endotoxin-induced fetal growth retardation in the pregnant guinea pig. Tumor necrosis factor-alpha in response to endotoxin administration in the pregnant guinea pig
- Abstracts: Large fetal heart rate decelerations at term associated with changes in fetal heart rate variation. Fetal cerebral, circulatory, and metabolic responses during heart rate decelerations with umbilical cord compression