Amniotic prolactin control over amniotic and fetal extracellular fluid water and electrolytes in the rhesus monkey

Administration of 1-10 mg ovine pituitary prolactin (oPRL) into the amniotic fluid of 10 rhesus monkeys in the last third of gestation consistently caused a decrease in amniotic fluid volume not seen when saline, vasopressin, or bovine serum albumin were injected into 9 other monkeys. The effects lasted for 24 h. Intraamniotic injection of 10 mg oPRL prevented or reversed a doubling of water and electrolyte content of the fetal extracellular fluid (ECF) volume in the face of hypertonic amniotic fluid. Efflux of these substances from the fetal ECF in the face of hypotonic amniotic fluid was similarly prevented or reversed by intraamniotic prolactin injection. Ovine PRL had no effect on fetal ECF water and electrolytes in the face of isotonic amniotic fluid. Possible sites of these oPRL effects were amnion, placenta, fetal lung and/or fetal gastrointestinal tract.