Processing of neuropeptide Y and somatostatin in human cerebrospinal fluid as monitored by radioimmunoassay and mass spectrometry

Carol Nilsson, Ann Westman, Kaj Blennow, Rolf Ekman

Research output: Contribution to journalArticle

19 Scopus citations

Abstract

The processing of four neuropeptides, neuropeptide Y (NPY) 1-36, NPY (18-36), somatostatin (SOM) 1-28, and SOM (15-28) was studied in human cerebrospinal fluid (CSF) by using a novel combination of methods that included radioimmunoassay (RIA) and mass spectrometry. Untreated CSF samples were chromatographed using reversed-phase high pressure liquid chromatography (RP-HPLC) followed by NPY-RIA or SOM-RIA. These results were compared with those obtained by incubating CSF with exogenous synthetic peptides and directly detecting peptide fragments by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-MS). Using this combination of methods, we were able to determine the probable identities of peptides/peptide fragments recognized in radioimmunoassays. The most important NPY-immunoreactive components in CSF were found to be NPY (1-36) and NPY (3-36). Metabolic products of SOM (15-28) were found to contribute to SOM-like immunoreactivity (SOM-LI) in CSF, but SOM (1-28) only to a lesser degree. Differences in the rate of neuropeptide processing were observed. These differences depended more on the length of the peptide than its sequence. NPY (18-36) and SOM (15-28) were rapidly and extensively processed, whereas NPV (1-36) and SOM (1-28) were processed much more slowly in CSF. The production of SOM (15-28) from SOM (1-28) by enzymes in CSF was not observed. Also, the presence of a disulfide bond in the somatostatins appeared to stabilize them against enzymatic digestion of the ring structure. The results detailed in this report confirm MALDI-MS important role in studies of neuropeptide processing in CSF.

Original languageEnglish (US)
Pages (from-to)1137-1146
Number of pages10
JournalPeptides
Volume19
Issue number7
DOIs
StatePublished - Jul 1 1998

Keywords

  • Cerebrospinal fluid
  • Mass spectrometry
  • Neuropeptides
  • Radioimmunoassay

ASJC Scopus subject areas

  • Biochemistry
  • Physiology
  • Endocrinology
  • Cellular and Molecular Neuroscience

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