β-Endorphin-immunoreactive components in human cerebrospinal fluid

Cerebrospinal fluid (CSF) from patients without neurological disorder was analyzed after Sep-Pak extraction for β-endorphin (β-EP)-immunoreactive components by combined reversed-phase high-performance liquid chromatography (HPLC) and radioimmunoassay. A C-terminal directed antibody detected one major immunoreactive component, probably identical with β-EP1–31. An N-terminal directed antibody detected several immunoreactive components. One co-eluted with β-EP1–31 but the others are probably C-terminal truncated or otherwise modified forms of β-EP1–31. However, they eluted differently from β-EP1–16 (α-endorphin), β-EP1–26, 1–27 and α,N- acetyl-β- EP1–31 . Alternatively, some of the fragments may represent C-terminal extended forms of pro-enkephalin A-derived Met-enkephalin. A Met-enkephalin antiserum detected several immunoreactive components probably representing N-terminal extended forms; neither of them were identical with the β-EP-immunoreactive components. The results illustrate the heterogeneity of the β-EP-immunoreactive components in CSF and the need to characterize the β-EP radioimmunoassay before its application to biological extracts.