Lack of correlation between amniotic fluid and maternal plasma contents of β-endorphin, β-lipotropin, and adrenocorticotropic hormone in normal and pathologic pregnancies

Abstract

Reported are the concentrations of beta-endorphin, beta-lipotropin, and adrenocorticotropic hormone (ACTH) in the amniotic fluid and plasma of 40 healthy pregnant women at different stages of gestation. Moreover, the amniotic fluid levels of the three peptides were evaluated in 20 other pregnant women affected by different pathologic conditions (Cooley's disease, gestosis, diabetes, placental insufficiency, etc.). A silicic acid extraction procedure was performed on the samples. Each extract was subjected to Sephadex G-75 column chromatography, and the two fractions corresponding to beta-lipotropin and beta-endorphin were collected, freeze-dried, and assayed by two specific radioimmunoassays. Levels of ACTH were measured by radioimmunoassay directly on the extracts. Levels of beta-endorphin in amniotic fluid showed the highest values in the first trimester (173 +/- 30 fmol/ml, mean +/- SEM) but were significantly decreased in the second (75.2 +/- 14) and third trimesters (14.3 +/- 1.8). An inverse trend characterized plasma levels of beta-endorphin, which showed a progressive increase from the first trimester to term (10.4 +/- 11.1). Amniotic fluid levels of beta-lipotropin remained stable during the first (48.6 +/- 6.3) and second (54.6 +/- 11.1) trimesters, but decreased significantly in the third trimester (17.9 +/- 2.3). The plasma concentrations of beta-lipotropin showed the highest levels in the first trimester (10.9 +/- 0.9), and decreased significantly at term (8.9 +/- 1.3). Last, amniotic fluid levels of ACTH decreased from 55.3 +/- 4.75 fmol/ml in the first trimester to 12.5 +/- 1.16 in the second trimester, and rose again in the third trimester to 34.4 +/- 6.6 fmol/ml. Plasma levels of ACTH were characterized in the first two trimesters by values twice those recorded for nonpregnant women, and decreased at term to 8.9 +/- 1.4 fmol/ml. In the pregnant patients with fetuses affected by Cooley's disease (second trimester) and in those with edema-proteinuria-hypertension (EPH) gestosis (third trimester), amniotic fluid levels of beta-endorphin, beta-lipotropin, and ACTH were in the same range as those in healthy pregnant women.