Figure 1. Serum N-Formylkynurenine Levels Increase with Age.
Mice of the indicated ages were sacrificed and blood collected by cardiac puncture. Serum was prepared and flash frozen in liquid nitrogen. Frozen samples were thawed and analyzed by RP-HPLC for the levels of N-formylkynurenine (NFK) as described in Methods. The units for the MS measurements in the Y-axis are mAU (milli Absorbance Units). Relative concentrations were determined by injecting equal volumes of undiluted serum extractions for all mice of each age group. Values represent the mean ± SD of 10 animals of each age.