title: Plasma sphingosine-1-phosphate measurement in healthy subjects: close correlation with red blood cell parameters.
abstract: BACKGROUND
  Since sphingosine-1-phosphate (Sph-1-P) plays an important role as an extracellular mediator through interaction with specific cell surface receptors, especially in the area of vascular biology and immunology/haematology, determination of its plasma concentration may become important from the clinical viewpoint. Thus, we attempted to develop a method of measuring the plasma Sph-1-P concentration for use in the clinical laboratory setting.
  
  
  METHODS
  After two-step lipid extraction, Sph-1-P was coupled with o-phthaldialdehyde, and the resultant fluorescent derivative was separated by high-performance liquid chromatography. C17-Sph-1-P was used as the internal standard, instead of dihydrosphingosine-1-phosphate, which had been used previously for the same purpose but was actually detected in plasma.
  
  
  RESULTS
  Our procedures for preparing the plasma samples and assay Sph-1-P were found to be satisfactory for clinical laboratory testing. The plasma Sph-1-P concentrations were significantly higher in men (413.1 +/- 52.0 nmol/L; mean +/- SD) than in women (352.4 +/- 39.7 nmol/L). Unexpectedly, strong positive correlations were found between the plasma Sph-1-P concentration and red blood cell (RBC)-related parameters, rather than platelet-related parameters.
  
  
  CONCLUSIONS
  Our present study confirmed the possibility of the clinical introduction of plasma Sph-1-P measurement, and in addition, suggested that RBCs may be involved in the regulation of plasma Sph-1-P concentrations.
authors.affiliation: Department of Clinical Laboratory, The University of Tokyo Hospital, Tokyo, Japan.
authors.forename: Ryunosuke
authors.initials: R
authors.lastname: Ohkawa
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Nakamura
authors.forename: Shigeo
authors.initials: S
authors.lastname: Okubo
authors.forename: Shigemi
authors.initials: S
authors.lastname: Hosogaya
authors.forename: Yukio
authors.initials: Y
authors.lastname: Ozaki
authors.forename: Minoru
authors.initials: M
authors.lastname: Tozuka
authors.forename: Noriko
authors.initials: N
authors.lastname: Osima
authors.forename: Hiromitsu
authors.initials: H
authors.lastname: Yokota
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Ikeda
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Yatomi
mesh_terms: D001774:Blood Chemical Analysis / Q000379:methods*; D004912:Erythrocytes / Q000378:metabolism*; D006262:Health; D006801:Humans; D008246:Lysophospholipids / Q000097:blood*; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000097:blood
chemical_list: D008246:Lysophospholipids; C060506:sphingosine 1-phosphate; D013110:Sphingosine