Figure 5.

Effect of storage conditions on relative sphingosine 1-phosphate (A,B) and sphinganine 1-phosphate (C,D) levels in human blood samples. (A–D) Plasma was directly separated from blood (EDTA as anticoagulant) as described in the Material and Methods section. (A,C) Plasma samples were deep frozen at −80 °C for 1 h and completely thawed at +22 °C for 30 min for the indicated number of freeze–thaw cycles. (B,D) Plasma samples were stored for 18 months at −80 °C before analysis. Plasma without freeze–thaw cycles (A,C) or long-term storage (B,D) served as the respective controls (100%). Data are shown as the mean (in %) ± SD (n = 4).