HIGH-LEVELS OF FETAL MEMBRANE ACTIVIN BETA-A AND ACTIVIN RECEPTOR-IIBMESSENGER-RNAS AND AUGMENTED CONCENTRATION OF AMNIOTIC-FLUID ACTIVIN-A IN WOMEN IN TERM OR PRETERM LABOR

The aim of the present study was to evaluate whether spontaneous labor at term and pathological preterm labor are associated with changes in the expression of activin A and activin receptor mRNAs in fetal membr anes. In addition, amniotic fluid activin A concentration in women del ivering at term or undergoing preterm labor was also measured. The exp ression of activin beta A subunit and activin receptor type II and typ e IIB mRNAs was assessed by reverse transcriptase-PCR on specimens of amnion and chorion collected from patients delivering at term or under going preterm labor, Control specimens were collected from women deliv ered by elective cesarean section who had not experienced labor. A spe cific two-site ELISA was used to measure activin A concentrations in t he amniotic fluid. A cross-sectional study of amniotic fluid retrieved by amniocentesis from 109 pregnant women was carried out. Patients we re classified into the following groups: (1) healthy controls at term but not in labor (n=25); (2) healthy controls at term in spontaneous l abor (n=40); (3) healthy controls between 23 and 36 weeks of gestation (n=12); (4) patients in preterm labor responding to tocolytic treatme nt (n=19); (5) patients in preterm labor with subsequent delivery (n=1 3). Activin beta A subunit and activin receptor type IIB mRNA levels i n both the chorion and amnion in women delivering at term or after pre term labor were significantly higher than in women delivering without undergoing labor (P<0.01). Expression of activin receptor type II mRNA in membranes did not differ among the three groups of women. Amniotic fluid activin A concentration in patients in labor was significantly higher than in those at term but not in labor (P<0.01). Patients in pr eterm labor had significantly higher amniotic fluid activin A concentr ations than women at the same stage of gestation (P<0.01). The highest values were found in women undergoing preterm labor and subsequent de livery. In conclusion, spontaneous labor and preterm labor are charact erized by increased synthesis and release of activin A from amniotic a nd chorionic cells and by an augmented expression of activin type IIB receptor.