title: Rapid extraction and separation of plasma beta-endorphin by cation-exchange high-performance liquid chromatography.
abstract: Cation-exchange high-performance liquid chromatography (HPLC) was used to increase the sensitivity and specificity of the radioimmunoassay of plasma beta-endorphin. Proteins were precipitated from a 0.5 to 2.5 ml sample of plasma with 60% acetonitrile at pH 4.7. The supernatant was subjected to cation-exchange HPLC. Gradient elution with volatile buffers was used to separate beta-endorphin from beta-lipotropin. The beta-endorphin fraction (1.8 ml) was concentrated by lyophilization and subjected to radioimmunoassay. In healthy pregnant women at labour plasma concentration of beta-endorphin varied from 105 to 403 pg/ml. In healthy non-pregnant women plasma concentration of beta-endorphin was low, exceeding the detection limit (4 pg/ml) of the assay in only one of the 7 subjects studied.
mesh_terms: D002851:Chromatography, High Pressure Liquid; D002852:Chromatography, Ion Exchange; D004723:Endorphins / Q000097:blood*; D005260:Female; D006801:Humans; D011247:Pregnancy; D011863:Radioimmunoassay; D001615:beta-Endorphin
chemical_list: D004723:Endorphins; D001615:beta-Endorphin