Avraham Golander

Paracrine and Autocrine Factors Involved in the Regulation of the Release of Human Decidual Prolactin and Human Placental Lactogen

During pregnancy, the decidua and placenta synthesise and secrete several protein hormones that have identical or nearly identical chemical and biological properties to protein hormones synthesised and secreted by the pituitary gland and other tissues. For example, human decidual tissue synthesises and releases protein hormones that are identical to pituitary prolactin1 and ovarian relaxin.2 The placenta synthesises and releases hCG and hPL which have striking chemical and biological similarities to LH and to growth hormone and prolactin, respectively.3 Nevertheless, despite the striking similarities between these hormones, the regulation of the synthesis and secretion of the protein hormones from the decidua and placenta is different from that of the pituitary protein hormones. Pituitary prolactin, growth hormone and most protein hormones are stored in large secretory granules, but ultrastructural and biochemical studies indicate that decidual prolactin4 and hPL5 are localised in the post-microsomal supernatants of decidual and placental tissue homogenates.

Synthesis of Prolactin by Human Decidua in Vitro

To determine whether human decidua and/or chorion synthesizes and secretes prolactin, explants of decidua obtained at Caesarian section and explants of chorion from the membranes separating dizygotic twins were cultured for periods of up to 6 days. The decidual explants released 366 +/- 37 ng prolactin/100 mg tissue (mean +/- S.D.) during each day in culture and incorporated 3H-labelled amino acids into immunoprecipitable prolactin. In the radioimmunoassay for prolactin, serial dilutions of incubation medium displaced 125I-labelled prolactin parallel to the displacement by pituitary prolactin and the prolactin in the medium eluted from Sephadex G-150 in a position indentical to that of pituitary prolactin. Chorionic explants released prolactin into the incubation medium during day 1 of culture only and did not incorporate 3H-labelled amino acids into prolactin. These results demonstrate that prolactin is synthesized by the decidua and not by the chorion and suggest that the decidua is the source of prolactin in amniotic fluid.

Prolactin Synthesis by Human Chorion-Decidual Tissue: A Possible Source of Prolactin in the Amniotic Fluid

Explants of human chorion-decidual tissue obtained at delivery from normal, full-term pregnancies synthesize and secrete prolactin. This hormone is indistinguishable from pituitary prolactin by chromatographic, electrophoretic, immunologic, and receptor assay techniques. These results suggest that chorion-decidua may be the source of the large quantities of prolactin in amniotic fluid.