Isolation of prolactin from human amniotic fluid.

Amniotic fluid, obtained from women at term, was centrifuged and concentrated by ultrafiltration. The concentrated amniotic fluid was purified by gel filtration on Sephadex G-100 and ion-exchanged chromatography on DEAE-cellulose. The fractions obtained during purification procedures were assayed for prolactin and somatotropin activities by respective radioimmunoassays. The prolactin-rich fraction obtained from ion-exchange chromatography was further purified by isoelectric focusing. A yield of 0.21 mg of highly pruified prolactin containing 40 units/mg was obtained from 1 liter of the amniotic fluid. The prolactin was free of somatotropin and human placental lactogen.