Determination of epoxyeicosatrienoic acids in human red blood cells and plasma by GC/MS in the NICI mode

Epoxyeicosatrienoic acids (EETs) are cytochrome P450 metabolites of arachidonic acid involved in the regulation of vascular tone. Despite the importance of EETs in a variety of physiological effects, few methods have been developed to quantify them in human blood. This led us to develop a method by GC/MS with negative ion chemical ionization. As EETs are primarily located in phospholipids, red blood cells (RBCs) and plasma phospholipids were hydrolyzed with phospholipase A2 after a solid phase extraction. Then, EETs were derivatized as pentafluorobenzyl esters, and [2H8]-arachidonic acid was used as internal standard for quantification. EETs were found to be at concentrations of 106 ± 37 ng mL−1 in plasma and 33.4 ± 8.5 ng/109 RBCs (mean ± S.D.) in 10 healthy volunteers. Their amount in RBCs was 3-fold that in plasma; both parameters proved to be well correlated.