Human beta-endorphin and beta-lipotropin levels in maternal and fetal plasma and amniotic fluid.

We measured beta-endorphin (beta-EP) and beta-lipotropin (beta-LPH) levels in human maternal and fetal plasma and amniotic fluid, simultaneously. It appeared evident that maternal circulating levels of beta-EP (n = 11, 163.9 +/- 12.9 pg/ml, mean +/- S.E.) and beta-LPH (n = 11, 413.0 +/- 25.9 pg/ml) at delivery were significantly (p less than 0.01) higher than those of maternal plasma at term (beta-EP; n = 4, 18.3 +/- 2.1 pg/ml, beta-LPH; 213.4 +/- 24.3 pg/ml) and those of amniotic fluid (beta-EP; n = 5, 8.5 +/- 1.2 pg/ml, beta-LPH; 215.1 +/- 44.9 pg/ml). Fetal beta-EP levels (n = 11, 79.1 +/- 5.8 pg/ml) were significantly (p less than 0.01) higher than those of amniotic fluid. These data suggest that the origin of amniotic fluid beta-EP may be an increased synthesis in the maternal and fetal pituitary gland but not in the placenta.