Prolactin and fetal osmoregulation: water transport across isolated human amnion.

The addition of human or ovine prolactin to the fetal side of the human amnion is associated with a latent decrease in membrane permeability. The specificity of this effect of prolactin is observed when equimolar concentrations of human placental lactogen and human growth hormone were used in place of ovine prolactin and failed to influence water transport. Likewise, the extracellular transport of p-aminohippurate across human amnion was unaffected by the addition of ovine prolactin. Tritiated water transport under these circumstances, however, remained impaired. The addition of antibody to ovine prolactin completely blocked the effect of this polypeptide on membrane permeability. Permeability to tritiated water remained unchanged when synthetic arginine vasopressin was added to the fetal side of the amnion. The results imply an active role for prolactin on water transport across human amnion. Moreover, the latent period between the addition of the polypeptide and its subsequent influence on permeability suggests a biologic effect of this hormone. That this effect is related to ion transfer remains to be shown.