title: Plasma and red blood cell beta-endorphin immunoreactivity in normal and complicated pregnancies: gestational age variation.
abstract: Recent observations suggest that there may be two pools of beta-endorphin-like immunoreactivity in mammalian circulation. One of these pools is present in plasma and the other is detected in association with erythrocytes. Elucidation of an erythrocyte-associated pool may explain some of the wide variability of plasma beta-endorphin levels reported in the literature. We measured beta-endorphin immunoreactivity levels in 85 normal and 33 complicated pregnancies to delineate a possible correlation between gestational age and beta-endorphin immunoreactivity levels in plasma and in erythrocytes. Our results indicate that beta-endorphin immunoreactivity levels in both plasma and erythrocytes vary systematically throughout the gestational period, reaching a peak at 31 to 32 weeks of gestation. Amniotic fluids at midgestation were also analyzed and no correlation was observed between the levels of beta-endorphin immunoreactivity and fetal sex. Compared to normal patients, diabetic patients had significantly lower levels of beta-endorphin immunoreactivity in plasma and higher levels in erythrocytes although the total beta-endorphin immunoreactivity was not statistically different from that in normal subjects. We conclude that (1) the total beta-endorphin immunoreactivity level in whole blood is much higher than that reported in plasma, (2) both plasma- and erythrocyte-associated beta-endorphin immunoreactivity levels vary with gestational age, with a peak level at 24 to 32 weeks of gestation, (3) amniotic fluid beta-endorphin immunoreactivity levels are unrelated to fetal sex, and (4) diabetic patients may have a different distribution of beta-endorphin immunoreactivity pools than normal individuals.
authors.forename: M I
authors.initials: MI
authors.lastname: Evans
authors.forename: A M
authors.initials: AM
authors.lastname: Fisher
authors.forename: A G
authors.initials: AG
authors.lastname: Robichaux
authors.forename: R C
authors.initials: RC
authors.lastname: Staton
authors.forename: D
authors.initials: D
authors.lastname: Rodbard
authors.forename: J W
authors.initials: JW
authors.lastname: Larsen
authors.forename: A B
authors.initials: AB
authors.lastname: Mukherjee
mesh_terms: D000653:Amniotic Fluid / Q000032:analysis; D004723:Endorphins / Q000097:blood*; D004912:Erythrocytes / Q000032:analysis*; D005260:Female; D005865:Gestational Age; D006801:Humans; D006973:Hypertension / Q000097:blood; D007745:Labor Onset; D010949:Plasma / Q000032:analysis; D011247:Pregnancy; D011248:Pregnancy Complications / Q000097:blood*; D011254:Pregnancy in Diabetics / Q000097:blood; D011863:Radioimmunoassay; D012732:Sex Determination Analysis; D001615:beta-Endorphin
chemical_list: D004723:Endorphins; D001615:beta-Endorphin