Comprehensive profiling of the human circulating endocannabinoid metabolome: clinical sampling and sample storage parameters

Clin Chem Lab Med. 2008;46(9):1289-95. doi: 10.1515/CCLM.2008.242.


Background: Endogenous cannabinoid-receptor ligands (endocannabinoids) and over a dozen related metabolites now comprise the "endocannabinoid metabolome". The diverse (patho)physiological roles of endocannabinoids, the predictive/diagnostic utility of systemic endocannabinoid levels, and the growing interest in endocannabinoid-related pharmacotherapeutics mandate a valid clinical protocol for processing human blood that does not jeopardize profiling of the circulating endocannabinoid metabolome.

Methods: We systematically evaluated the potential effect of pre-analytical variables associated with phlebotomy and sample handling/work-up on the human-blood endocannabinoid metabolome as quantified by state-of-the-art liquid chromatography-mass spectrometry.

Results: Neither subject posture during phlebotomy nor moderate activity beforehand influenced the blood levels of the 15 endocannabinoid-system lipids quantified. Storage of fresh blood at 4 degrees C selectively enhanced ethanolamide concentrations artifactually without affecting monoglycerides and nonesterified fatty acids, such as arachidonic acid. In marked contrast, ethanolamides and monoglycerides remained stable through three plasma freeze/thaw cycles, whereas plasma arachidonic acid content increased, probably a reflection of ongoing metabolism.

Conclusions: Class- and compound-selective pre-analytical influences on circulating human endocannabinoid levels necessitate immediate plasma preparation from fresh blood and prompt plasma apportioning and snap-freezing. Repeated plasma thawing and refreezing should be avoided. This protocol ensures sample integrity for evaluating the circulating endocannabinoid metabolome in the clinical setting.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Animals
  • Blood Circulation*
  • Blood Specimen Collection / methods*
  • Cannabinoid Receptor Modulators / blood*
  • Cannabinoid Receptor Modulators / isolation & purification
  • Cannabinoid Receptor Modulators / metabolism*
  • Cattle
  • Endocannabinoids*
  • Female
  • Humans
  • Motor Activity
  • Posture
  • Reference Values
  • Sensitivity and Specificity
  • Temperature


  • Cannabinoid Receptor Modulators
  • Endocannabinoids