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.