CHARACTERIZATION OF IMMUNOREACTIVE DYNORPHIN-B AND BETA-ENDORPHIN IN HUMAN PLASMA

Dynorphins and beta-endorphin in human plasma were characterized and s tudied quantitatively using radioimmunoassay, high-performance liquid chromatography (HPLC), and mass spectrometry. Most immunoreactive (ir) dynorphin B and beta-endorphin in human plasma coeluted with authenti c peptides in analysis. Dynorphin A was not detected. Added to human p lasma it was rapidly converted into Leu-enkephalin-Arg(6) followed by elimination of the C-terminal arginine after prolonged incubation. The rate of dynorphin A conversion was estimated at 40 pmol/min/mu l plas ma. This process was inhibited by the thiol protease inhibitor, PHMB a nd by EDTA. Dynorphin B, alpha-neoendorphin and big dynorphin were vir tually not metabolized by plasma proteases under the same conditions. beta-endorphin was processed into beta-endorphin(1-19) and the corresp onding C-terminal counterpart p-endorphin(20-31) at a rate of about 25 pmol/min/mu l of plasma. Based on the above data, a reliable strategy was established to measure dynorphin B- and beta-endorphin-ir in huma n plasma samples. The basal levels in a male control group were 0.99 /- 0.11 (n = 11) and 16.3 +/- 1.5 (n = 11) fmol/ml plasma, respectivel y. (C) 1998 Elsevier Science Inc.