Search

A link between intrauterine infection and premature labor is widely accepted, yet the fetal inflammatory responses to such infections are not well understood. Our aim was to use a sheep model in which an inflammatory state was induced by lipopolysaccharide (LPS) administration during pregnancy to the maternal systemic, intra-amniotic or extra-amniotic compartments. Fetal and maternal blood gases and uterine electromyographic activity along with fetal and maternal circulating concentrations of prostaglandins PGE2 and PGFM, cortisol, and interleukin-6 were determined. Maternal systemic LPS treatment resulted in mild maternal hypoxemia, a rise in temperature, greater fetal hypoxemia, and a marked rise in fetal cortisol and PGE2 concentrations that persisted for 48 h. Intra-amniotic administration of LPS at doses higher than those used systemically caused an increase in fetal cortisol and PGE2 concentrations as well as a rise in uterine activity, but these were lesser in magnitude. Extra-amniotic LPS administration caused no overt fetal or maternal inflammatory responses. We conclude that maternal LPS treatment markedly elevated fetal cortisol and PGE2 concentrations. This may be a potential protective mechanism that aids the fetus in the event of premature delivery. The attenuated fetal response to intra-amniotic LPS treatment, despite the much higher dose used, may support a role for the amniotic fluid in protecting the fetus from endotoxin exposure during pregnancy.

Unlabelled: In this study, we investigated the timing of changes in aromatase, estradiol receptor, and oxytocin receptor expression in ovine uterine and placental tissues before parturition. Labor was induced by betamethasone injection into the fetus on Days 130-132 of pregnancy. Tissue samples were collected at injection and then every 14 h until labor (56 h) from four ewes at each time point. Samples were analyzed for aromatase, estradiol receptor, and oxytocin receptor expression by in situ hybridization; for oxytocin binding to its receptor using a specific antagonist; and for estradiol receptor quantitation by immunocytochemistry. Aromatase mRNA expression increased by 14 h postinjection (p < 0.02) in the fetal villi and remained high until labor. Expression of estradiol and oxytocin receptor mRNAs was unchanged in myometrium but increased in the endometrial luminal epithelium by 28 h (p < 0.05) and remained high until labor. Estradiol receptor protein concentration increased modestly at labor while oxytocin receptor binding in the luminal epithelium changed in parallel to the mRNA concentration., In Conclusion: 1) induction of aromatase may facilitate the expression of endometrial estradiol and oxytocin receptors in the placentome, 2) changes in endometrial rather than myometrial oxytocin receptor may be important in inducing parturition, and 3) the transcription of estradiol receptor and oxytocin receptor in the uterine epithelium are positively correlated during parturition.

In a preliminary study, allantoic fluid collected from pregnant sheep across gestational ages of 20-124 days contained significantly higher levels of activin bioactivity (189 +/- 74 ng/ml, mean +/- SE) than did amniotic fluid (3.2 +/- 0.6 ng/ml). Using a combination of chromatography steps, we isolated from 5 L of allantoic fluid approximately 612 microg of immunoactive activin, which eluted over 10 fractions from a C8 reversed-phase column. When these fractions were assayed in a rat pituitary cell culture bioassay, in a specific RIA, and in an activin A two-site ELISA, the RIA activity was skewed to the less hydrophobic side of the activin profile, while the bioactivity was skewed to the more hydrophobic forms. The activity measured in the two-site ELISA more closely matched the mass of activin as determined by laser densitometry. Amino-terminal sequencing of fractions containing either peak immunoactivity or bioactivity showed each to be identical to activin A. This was confirmed by internal sequences from a fraction that eluted in the area of overlapping immunoactivity and bioactivity. A peptide containing at least 18 amino acids at its amino terminus, which were identical to the conserved region of the acute-phase protein serum amyloid A, was identified in the most immunoactive activin fractions.