High-performance liquid chromatograpy-thermospray mass spectrometry of omega-hydroxy polyunsaturated fatty acids from rat brain homogenate.

A method for the analysis of omega-hydroxy polyunsaturated fatty acids (omega-HPUFAs) in rat tissue homogenate, supplemented with NADPH and homo-gamma-linolenic acid [20:3(n-6)], arachidonic acid [20:4(n-6)], eicosapentaenoic acid [20:5(n-3)] or docosahexaenoic acid [22:6(n-3)] as a substrate was developed. By ion analysis of chromatograms obtained with reversed-phase HPLC-thermospray MS, many omega-HPUFAs corresponding to each precursor fatty acid could be characterized by the high intensity of the molecular ion (MH+) and quasimolecular ion (MNH4+, MNa+), while other common HPUFAs were characterized by the high intensity of the base ion of MH+--H2O. On a selected-ion monitoring chromatogram of rat brain homogenate, significant amounts of omega-HPUFA from each precursor fatty acid, especially from 22:6(n-3), were detected compared with the amounts found in rat large intestine homogenate. Based on these results, a highly active NADPH-dependent omega-oxidation system is suggested for rat brain homogenate resulting in extensive oxidation of 22:6(n-3).