Concentration of annexin V in gestational tissues: placenta, fetal membranes, myometrium and amniotic fluid

THE BACKGROUND: It is believed that annexin V, an anticoagulant protein abundant in trophoblast, prevents circulating blood in the intervillous space from hypercoagulability and fibrin deposition. Distribution and the role of annexin V localized in other gestational tissues like myometrium and fetal membranes, as well as in amniotic fluid is unknown. The aim of this study was to determine the concentration of annexin V in the tissues under consideration. STUDY DESIGN: The study group consisted of 40 healthy women at the 1st stage of labour, 16 of whom delivered by cesarean section. The strips of myometrium, placenta and fetal membranes, as well as the samples of amniotic fluid and the venous blood, were collected during surgery. Homogenates were prepared from the tissues. Annexin V was measured by immunoenzymatic method (ELISA). RESULTS: Concentration of annexin V in the placenta was 122.65 +/- 33,14 ng/mg protein, in fetal membranes 136.31 +/- 49.30 ng/mg protein and in myometrium 65.40 +/- 30.72 ng/mg protein. There was a statistical difference between the concentrations in placenta and fetal membranes vs. myometrium (p<0.05). In amniotic fluid annexin V was found to be in low concentration (4.46 +/- 2.59 ng/ml, i.e., 1.60 +/- 1.21 ng/mg protein) while in blood plasma it was extremely low, over 6000 times lower than in placenta. CONCLUSION: Annexin V is present not only in placenta, but also in fetal membranes and myometrium. Its concentration in fetal membranes is similar to that in placenta, while in myometrium it is 50% lower. Annexin V found in newly discovered sites probably plays a similar role like placental annexin V.