Combined high-performance liquid chromatographic-radioimmunoassay method for the analysis of endorphins, enkephalins and other neurotransmitter peptides.

Assays for beta-endorphin (BE) and its precursors such as beta-lipotropin (LPH) in cerebrospinal fluid (CSF), plasma and some tissues have been difficult because of their low concentrations in limited sample volumes, the non-specificity of most antisera. These problems are compounded by the lack of suitable separation methods. Similar problems exist for the enkephalins, tachykinins and dynorphins, among others. This study reports a high-performance liquid chromatographic (HPLC) separation method in which BE and LPH are well separated from each other and which also separates other neuropeptides of interest. The method uses volatile solvents which do not interfere with radioimmunoassay (RIA). Thus by combining HPLC with RIA the method offers, for the first time, a specific assay method for the endorphin, enkephalin and dynorphin families of peptides which does not suffer from the uncertainties in RIA due to cross-reactivities of antisera. Peptide concentrations obtained from the CSF of a small group of chronic pain patients are also presented.