Impact of the FAAH inhibitors URB597 and AA-5HT on levels of FAAH substrates in MSCs. Cells were treated with vehicle or FAAH inhibitors (10 μM) for 6 h. Concentrations of endocannabinoids and endocannabinoid-like substances were quantified from cell lysates by LC-MS. All concentrations were normalized to cellular protein amounts. Percent control refers to comparison with respective vehicle controls (100%). Vehicle controls of FAAH inhibitors are indicated as one dotted line in the scatter dot plot. For calculation of the respective percentage stimulation, the corresponding vehicle controls for URB597 (n = 4) and AA-5HT (n = 3) were used. Horizontal lines in the scatter dot plot indicate the respective mean of the indicated single experiments from n = 4 donors (URB597) or n = 3 donors (AA-5HT). Basal concentrations of FAAH substrates measured in vehicle-treated cells were 1.13 ± 0.29 pmol/mg protein (AEA), 24.62 ± 2.42 pmol/mg protein (2-AG), 6.20 ± 1.37 pmol/mg protein (OEA), and 4.13 ± 0.87 pmol/mg protein (PEA) (mean ± SEM from single experiments from n = 4 donors), respectively.