[Mass-spectrometric measurements of P450 isoform specific content and corresponding enzyme activities].

Mouse cytochrome P450 subfamily 1A, 3A, 1E, 2C, 2D isoenzyme activities and corresponding contents were measured by means of triple quadrupole mass spectrometer in Multiple Reaction Monitoring mode (MRM). The technique was developed and tested on microsomes from control mouse and after induction with phenobarbital or methylcholanthrene. MRM allowed us to measure the content of individual P450 isoforms without using isotopic-labeled peptides or derivatization reagent. The results of modifying the content of certain P450 isoforms correlated with the change of enzymatic activity, defined by marker substrates.