Immunoreactive orexin-A in human plasma

Peptides. 2001 Jan;22(1):139-42. doi: 10.1016/s0196-9781(00)00369-7.


Orexin-A and orexin-B are newly discovered neuropeptides which are implicated in feeding behavior and arousal state. We studied immunoreactive(IR)-orexin-A concentrations in human plasma by radioimmunoassay. IR-orexin-A concentrations in plasma obtained from 17 healthy subjects in the morning were 1.94 +/- 0.24 pmol/liter (mean +/- SEM). IR-orexin-A levels in the plasma obtained at night were not significantly different from those obtained in the morning in 9 female subjects. The HPLC analysis of the plasma extract showed two immunoreactive peaks; one peak eluting in an identical position to synthetic orexin-A, and one eluting earlier. This study has shown for the first time the presence of orexin-A in human plasma.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Carrier Proteins / blood*
  • Chromatography, High Pressure Liquid
  • Female
  • Humans
  • Intracellular Signaling Peptides and Proteins*
  • Male
  • Middle Aged
  • Neuropeptides / blood*
  • Orexins
  • Radioimmunoassay


  • Carrier Proteins
  • HCRT protein, human
  • Intracellular Signaling Peptides and Proteins
  • Neuropeptides
  • Orexins