Production and localization of human prolactin in placenta and decidua in early and at term normal pregnancy.

Prolactin (PRL), a peptide hormone of the anterior pituitary, greatly increases in both plasma and amniotic fluid during pregnancy. The pattern of measurable PRL differs according to gestational stage and between plasma and amniotic fluid levels. This variation has led to several opinions regarding the production site of PRL during pregnancy. In this paper, the authors describe the production and localization of PRL-materializing tissues of human placenta and decidua both in early pregnancy and at term. Immunohistologic investigations with highly purified antiserum obtained by immunization of albino rabbits and reacted with human PRL alone revealed that syncytial trophoblast was a site of PRL production. PRL was also detected in decidual tissue, but the latter did not show a pattern of production. By a method of double staining, the production and localization of either anti-beta-subunit of human chorionic gonadotropin (hCG-beta) or human placental lactogen (hPL) were manifestly differentiated from those of PRL in syncytial trophoblast.