Fig. 2.

Cytochrome P450 quantitation in murine liver microsomes and tissue lysates. Liver microsomes, kidney, lung, brain, intestine, and heart were prepared from pregnant mice, fetuses, and male and female Balb/c mice 3–4 weeks, 9–10 weeks, and 8–10 months of age. The proteins were harvested from four individual age- and sex-matched mice and pooled. The resulting pooled samples were then assayed in triplicate. Proteins were analyzed using the targeted SRM assay on a Thermo TSQ Vantage triple quadrupole mass spectrometer. Color coding denotes the abundance of each P450 enzyme measured using the peptides listed in Table 1. The asterisks indicate P450 enzymes subjected to absolute quantitation using isotopically labeled peptides. Unlabeled-peptide synthetic standards were used to perform relative quantitation of all other P450 proteins. Quantitation was performed using Skyline software, and peak signal-to-noise ratio was manually validated.