Radioreceptor assay of methionine-enkephalin-like substance in human cerebrospinal fluid

A sensitive and simple radioreceptor assay system for measuring methionine(met)-enkephalin-like substance in human cerebrospinal fluid (CSF) was developed using a particulate fraction of rat brain as a receptor preparation and [³H]dihydromorphine as a radiolabeled ligand in the presence of 1 mM ethylenediamine tetraacetate (EDTA) and 2 mM magnesium acetate. Metenkephalin-like substance was purified from CSF by the combination of Sephadex G-10 and SP-Sephadex (H⁺) column chromatographies to be free of sodium and large molecular weight substance such as β-endorphin. The assays were carried out on samples obtained from normal subjects and patients with the disease of the brain or pituitary by lumbar or ventricular puncture. Mean level in samples obtained from normal subjects by lumbar puncture was 2.6 ± 1.0 pmoles/ml.