Figure 1.

Typical chromatograms for LC-MS method specificity and selectivity. The retention times of representative peptides for rat COXs and human COXs were at 4.9, 2.6, 5.8 and 6.5 min, respectively (A–D). For Raw264.7 cells with LPS treatment, signal was only detected in rodent COX-2 MRM transition while it was below the detection limit in rodent COX-1 transition (E and F). No interference was found in human COX-1 and COX-2 transition (G and H). For EOMA cells with LPS treatment, signal was detected in rodent COXs’ transitions but not interfered in human COXs’ transitions (I–L). Similarly, the signal was only detected in human COXs’ transitions for the human recombinant enzymes samples and no background interference was found in rodent COXs’ transitions (M–T).