High fetal urocortin levels at term and preterm labor

CONTEXT

Placental urocortin has a role in the cascade of events leading to parturition by stimulating myometrial contractility and placental uterotonins secretion.

OBJECTIVE

The objective of this study was to evaluate urocortin levels in maternal and fetal [umbilical cord artery (UCA) and vein (UCV)] plasma at term and preterm labor.

DESIGN

The study design was a controlled cross-sectional study performed from November 2003 to June 2004.

SETTING

This study was performed at the Division of Obstetrics and Gynecology, University of Siena (Siena, Italy).

PATIENTS

Plasma samples were collected at term in the absence of labor (TNL; n = 27; 39.3 +/- 0.1 gestational weeks), at term spontaneous vaginal delivery (TL; n = 24; 40.1 +/- 0.2 gestational weeks), and at preterm labor (PTL; n = 19; 32.4 +/- 0.4 gestational weeks). Changes in urocortin mRNA expression were also evaluated in placentas collected from TNL (n = 11), TL (n = 11), and PTL (n = 10).

INTERVENTION

Urocortin levels were measured by specific RIA. Changes in placental mRNA expression were determined by real-time quantitative RT-PCR analysis.

RESULTS

Maternal and UCA plasma urocortin levels were significantly (P < 0.0001 for all) higher in TL and PTL than in TNL. Furthermore, UCA concentrations were significantly (P < 0.0001 for all) higher than and correlated with maternal concentrations (TNL: r = 0.45; P < 0.05; TL: r = 0.959; P < 0.0001; PTL: r = 0.7719; P < 0.0001). UCV levels were significantly (P < 0.001) higher in TL and PTL than in TNL and were significantly (P < 0.0001 for all) higher than and significantly (P < 0.0001 for all) correlated with maternal values, but were significantly (P < 0.0001 for all) lower than and correlated with UCA values (TNL: r = 0.9548; P < 0.0001; TL: r = 0.927; P < 0.0001; PTL: r = 0.838; P < 0.0001). Placental urocortin mRNA expression did not differ among TNL, TL, and PTL samples.

CONCLUSIONS

Fetal urocortin secretion is increased in term and preterm labor. Whether these changes are a consequence rather than a cause of human parturition remains to be addressed.

Abnormal Umbilical Artery Doppler Waveforms and Cord Blood Inhibin A and Inhibin B Levels

Inhibin A and inhibin B are glycoprotein hormones produced by human placenta and by several fetal organs during pregnancy. They are secreted in maternal circulation in increasing amounts from early until term pregnancy, and in umbilical cord blood levels are significantly lower than in maternal serum and do not differ from mid-pregnancy to term gestation. In the present study, we aimed to determine whether secretion of inhibin A and inhibin B into the fetal circulation is increased in pregnancies complicated by umbilical-placental vascular insufficiency. A group of women (n = 13) with abnormal Doppler umbilical artery flow velocimetry and a group of control women (n = 11) with uncomplicated term pregnancies and normal umbilical artery flow velocity waveforms were studied. In each woman, inhibin A and inhibin B concentrations were estimated in umbilical cord artery and vein. In the two groups of women, mean inhibin A levels did not differ between umbilical cord artery and vein. In addition, no difference was retrieved both in umbilical cord artery and vein values between healthy controls and patients with abnormal Doppler umbilical artery flow velocimetry. On the contrary, inhibin B levels were significantly higher in samples from umbilical cord vein than artery, in both groups of pregnant women (both p < 0.001). However, women with abnormal Doppler umbilical artery flow velocimetry had inhibin B levels significantly higher than healthy controls (p = 0.005) only in the umbilical cord artery, but not in the vein. In the presence of abnormal Doppler umbilical artery flow velocity, the concentrations of inhibin B are increased in the arterial umbilical circulation, suggesting that inhibin B is released from multiple fetal sources as a response to hypoxemic stress. As inhibins may affect the hypothalamus-pituitary-adrenal axis which plays an important role in the mechanisms of adaptations to the post-natal life, inhibin B in fetal circulation might then be beneficial to a fetus whose intrauterine survival is threatened by impaired umbilical-placental blood flow.

Serum inhibin B correlates with successful ovulation in infertile women

PURPOSE

To investigate whether inhibin B and activin A serum and follicular fluid levels in infertile women undergoing induction of superovulation correlate with successful ovulation.

METHODS

Infertile women (n = 16) (30-43 years of age) undergoing induction of superovulation for assisted reproduction were studied. A blood sample was collected before and days 3, 8, and 12 during the induction of superovulation. A follicular fluid sample at the time of ovarian pick up was also collected. Serum and follicular fluid were assayed for inhibin B, activin A, and estradiol.

RESULTS

According to the successful follicular development women were divided in two groups: (A) responders (n = 10) and (B) poor responders (n = 6). Women of group A showed mean follicular fluid inhibin B levels higher than in group B (P = 0.001), while no significant difference for activin A levels was found. During induction of superovulation serum activin A levels did not change in both groups of women, while inhibin B and estradiol levels significantly increase only in responder women (P < 0.001). Serum inhibin B and estradiol levels correlated with follicles developed > or = 10 mm (P = 0.000).

CONCLUSIONS

Serum inhibin B is an effective marker of follicular development in infertile women undergoing induction of superovulation, and may represent a further marker for ovarian follicular capacity.

Inhibin A, inhibin B and activin A concentrations in umbilical cord artery and vein

Activin A and inhibins (A and B) are growth factors expressed during pregnancy by the human placenta, decidua and fetal membranes, and by several fetal organs. They are secreted in both the maternal and the fetal circulations, but the net contribution of the fetus to inhibins/activin A production is still unclear. In the present study we determined whether there was a difference in the serum concentration of activin A, inhibin A and inhibin B between the artery and vein of the umbilical cord. Arterial and venous umbilical cord blood was obtained immediately before elective Cesarean section of 16 term infants from uncomplicated pregnancies. Inhibins and activin A levels were assayed by specific enzyme-linked immunosorbent assays. The paired t-test and linear regression analysis were used to calculate statistical significance. Inhibin A levels did not differ between the artery and vein of the umbilical cord. In contrast, arterial inhibin B levels were significantly (p < 0.001) lower, and activin A concentrations significantly (p < 0.05) higher than the respective venous concentrations. A significant correlation between arterial and venous levels of inhibin A (r = 0.591; p < 0.05), inhibin B (r = 0.749; p < 0.0001) and activin A (r = 0.571; p < 0.05) was found. The present findings suggest that the human placenta is the main source of inhibin B, and the fetus of activin A, in the umbilical cord. In light of the possible roles played by inhibin and activin in erythroid differentiation, protection of neurons against brain injury and modulation of adrenal and pancreatic hormone release, the present data may be of help in evaluating their changes in the umbilical cord when gestational diseases occur.