Sources and Disposition of Pituitary Prolactin in Maternal Circulation, AmnioticFluid, Fetus and Placenta in the Pregnant Rhesus Monkey

Abstract

Experiments performed at 130 days gestation in 11 rhesus monkeys revealed a positive correlation between pituitary prolactin concentrations in maternal plasma, but not fetal plasma, and those in amniotic fluid. Minute amounts of radioactively-labeled prolactin passed between maternal and fetal circulation. Small amounts of labeled hormone also passed from the mother, but not from the fetus, to the amniotic cavity. Fetal plasma prolactin was elevated by fetalinjection of thyrotropin-releasing factor (TRF), but not to an extent comparable to maternal plasma rises seen after the hypothalamic hormone was injected into the mother. Fetal tissues andthe placenta acquired protein-bound radioactivity when ^l25I-labeled prolactin was injected intothe amniotic fluid, the ¹²⁵I in the former organ being displaced by incubation with nonlabeled prolactin. It was concluded that the maternal circulation may be a major source of amniotic fluid prolactin, while fetal and maternal circulations show mutually, essentially independent prolactin levels, which are separately but unequally affected by TRF effects on secretion of the hormone by the 2 pituitary glands. The placenta as well as the fetus and/or mother appear to be destinations of amniotic prolactin. (Endocrinology94: 1364, 1974)