The binding of endogenous and exogenous substance-P in human plasma

Biochem Pharmacol. 1990 Apr 1;39(7):1161-6. doi: 10.1016/0006-2952(90)90257-l.


High levels of substance-P are present in the plasma of patients with carcinoid tumours and some thyrotoxic conditions. The majority of the substance-P in the blood plasma was shown, by immunoassay, to be associated with high molecular-weight material in a complex that could be dissociated by repeated gel-filtration. Smaller amounts of an intermediate molecular-weight (about 65,000 Da) complex were also detected. Chemical crosslinking with glutaraldehyde was used to show that the radioactively-labelled derivative [125I]Tyr-8-substance-P was able to bind to the high-Mr fraction of human plasma and also to human serum albumin. Binding to serum albumin was also demonstrated by equilibrium gel-filtration. Substance-P added to human plasma from a thyrotoxic subject, which contained high endogenous levels of the tachykinin (980 pg/mL), was rapidly degraded during incubation at 37 degrees, whereas the endogenous substance-P was considerably more stable. These results suggest that the binding of substance-P to blood plasma components may play an important role in protecting it against degradation. Furthermore, immunoassay techniques involving prior extraction, which fail to detect the bound substance-P, will give inaccurate measurements of the levels of this peptide in plasma.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Chromatography, Gel
  • False Positive Reactions
  • Humans
  • Intercellular Signaling Peptides and Proteins
  • Molecular Weight
  • Peptides / blood*
  • Protein Binding / drug effects
  • Radioimmunoassay
  • Substance P / analogs & derivatives*
  • Substance P / blood*
  • Substance P / pharmacology
  • Temperature


  • Intercellular Signaling Peptides and Proteins
  • Peptides
  • substance P, iodo-Tyr(8)-
  • substance P-like peptides
  • Substance P