There is compelling evidence that amniotic fluid prolactin originates from the decidua rather than the maternal or fetal pituitary glands. For example, in human and in rhesus monkey pregnancy, amniotic fluid levels of prolactin are 10- to 50-fold higher than in maternal or fetal blood. Also, in the rhesus monkey, the quantities of prolactin in amniotic fluid at early, mid, and late gestation reflect the capacity of the decidua to synthesize and secrete prolactin. Suppression of maternal serum prolactin concentrations by hypophysectomy or bromocriptine therapy does not reduce amniotic fluid prolactin concentrations. The protein structure of decidual prolactin is identical to that of pituitary prolactin, but the cellular regulation of the synthesis and secretion of decidual prolactin differs markedly from that of pituitary prolactin. Finally, decidual prolactin is regulated by a different promoter region on the prolactin gene than pituitary prolactin. buy prednisone
There is no evidence that decidual prolactin is secreted into the maternal or fetal circulation. Thus, it likely acts as an autocrine/paracrine regulator of uterine, placental, or fetal membrane function, but its precise physiological role is not immediately apparent. Because prolactin affects water and ion transport in lower vertebrates and because prolactin treatment alters the permeability of fetal membranes, it has been proposed that decidual prolactin plays a role in controlling amniotic fluid volume.