Fig. 3. 5-HT is metabolized by CYP1A1 and is not converted to 5-HIAA. Human recombinant CYP1A1 (40 nM) (A) or negative control microsomes (B) were incubated with 5-HT (1 μM) and 5-HT levels in the presence of absence of co-factor NADPH was measured by LC-MS/MS at the indicated time points (0 - 60 min). Data are shown as the percentage of 5-HT at the indicated time point relative to 0 min. Representative chromatograms showing the 5-HT peak over time in the presence of NADPH are also shown (n = 3). (C) 5-HIAA was measured in the reaction mixture after 60 min in the presence of NADPH (blue) and a 100 nM 5-HIAA standard was also measured (red).