title: Determination of plasma beta-endorphin and beta-lipotropin by cation-exchange liquid chromatography and radioimmunoassay.
abstract: In this method for rapid separation of beta-endorphin (beta-EP) and beta-lipotropin (beta-LPH) in plasma, most of the plasma proteins in a 0.5- to 2.0-mL sample of plasma are precipitated with acetonitrile at pH 4.7. beta-EP and beta-LPH in the supernate are completely separated by liquid chromatography on a cation-exchange column, with gradient elution with volatile buffers, and are eluted in 1.5- to 2.0-mL volumes. After lyophilization, the redissolved beta-EP and beta-LPH are determined by radioimmunoassay. The respective mean concentrations of immunoreactive beta-EP and beta-LPH in plasma of nonpregnant women were 4.0 (SD 2.0) and 5.1 (SD 3.0) pmol/L; during labor, 33.3 (SD 25) and 69.6 (SD 41) pmol/L; and in venous plasma from umbilical cords after spontaneous labor, 38.6 (SD 18) and 38.7 (SD 19) pmol/L.
authors.forename: T
authors.initials: T
authors.lastname: Laatikainen
authors.forename: K
authors.initials: K
authors.lastname: Salminen
authors.forename: U H
authors.initials: UH
authors.lastname: Stenman
authors.forename: J
authors.initials: J
authors.lastname: Leppäluoto
mesh_terms: D000097:Acetonitriles; D002411:Cation Exchange Resins; D011232:Chemical Precipitation; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D004723:Endorphins / Q000097:blood*; D005260:Female; D005312:Fetal Blood / Q000032:analysis; D005612:Freeze Drying; D006801:Humans; D007231:Infant, Newborn; D007743:Labor, Obstetric; D011247:Pregnancy; D011863:Radioimmunoassay; D001615:beta-Endorphin; D008083:beta-Lipotropin / Q000097:blood*
chemical_list: D000097:Acetonitriles; D002411:Cation Exchange Resins; D004723:Endorphins; D001615:beta-Endorphin; D008083:beta-Lipotropin; C032159:acetonitrile