Immunoreactive endorphin peptides and prolactin in umbilical vein and maternal blood.

Immunoreactive endorphin peptides (ir EP) and prolactin (PRL) were measured by radioimmunoassay in venous blood from the umbilical cord of 86 neonates, 23 postpartum mothers, and 40 randomly selected blood bank donor control subjects. We also assayed these hormones in serosanguineous placental tissue fluid following delivery. The data suggest both ir EP and PRL are elevated during both processes and that placental chemistry may be implicated in blood levels of these hormones. Some biological and clinical aspects of placental opiates are discussed.