Prolactin bioactivity following decidual synthesis and transport by amniochorion

Current evidence suggests that high concentrations of prolactin in human amniotic fluid result from the transport of human decidual prolactin across reflected amniochorion. In this study, tritiated leucine placed on the isolated maternal side of amniochorion with adherent decidua was incorporated into newly synthesized tritiated human decidual prolactin. Identification of tritiated decidual prolactin on the fetal side of suspended membranes was confirmed within 4 hours of incubation. A heterologous species of human decidual prolactin identified on the maternal side of membranes was also detectable on the fetal side, and its bioactivity was found to be equivalent in both fetal and maternal chambers separated by amniochorion. These results confirm the de novo synthesis of human decidual prolactin and transport by amniochorion to the fetal side. Subsequent to transport, the biologic activity of human decidual prolactin is retained. Thus concentrations and biologic activity of amniotic-fluid prolactin can be accounted for by the transport of newly synthesized human decidual prolactin by the reflected amniochorion.