Quantitative assay for bradykinin in rat plasma by liquid chromatography coupled to tandem mass spectrometry

An assay to quantify bradykinin in rat plasma has been developed and validated, using liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). Sar-D-Phe(8)-des-Arg(9)-bradykinin was used as internal standard. Aprotinin was added to rat plasma to inhibit the activity of proteinases. Recoveries for solid-phase extraction (SPE) on Strata X reversed phase were greater than 80%. Multiple reaction monitoring (MRM) on a triple quadrupole mass spectrometer equipped with an electrospray source (ESI), operating in the positive ion-mode, was used for detection. The assay was validated and stability was explored. Bradykinin (10-500 ng/mL) was quantified with accuracy values (% RE) below 10% and intra- and inter-day precisions (% RSD) below 12 and 16%, respectively, for all concentrations. The method was successfully applied to several plasma samples from low levels kallikrein rats (LKRs) compared with normal kallikrein rats (NKRs).