Nuova metodica LC-MS/MS per la determinazione di peptidi endogeni nel plasma di ratto

Aim: Kinin-kallikrein and renin-angiotensin systems are strictly connected and involved in the control of blood pressure. In this work we quantify the major mediators of these two systems in a rat strain with low urinary kallikrein levels (LKRs). We hypothesize that LKRs has lower amounts of kinins and higher angiotensin II (ANG II) levels whencompared to a normal rat strain (NKRs). Methods: 46 plasma samples were analyzed (23 from LKRs and 23 from NKRs) using radioimmunoassay (RIA) and liquid chromatography coupled to tandem mass spectrometry (LCMS/MS). RIA assay wasdeveloped following RIA kit’s guidelines. An LC-MS/MS assay has been developed, validated and used for the quantification of bradykinin (BK). An elution gradient in a total run time of 12 minutes was used. The mass spectrometer was operated in positive ion-mode. ANG II plasma levels were lower than the sensitivity limit of the LC-MS/MS method developed. Results: We found lower BK concentrations in the LKRs compared to the NKRs; the average plasma BK concentration was 34.3 ± 1.29 ng/mL in NKRs versus 19.2 ± 0.92 ng/mL in LKRs. Furthermore ANG II levels were significantly higher in the LKRs, compared with the NKRs (90 ± 8 versus 74 ± 9 pg/ml in LKRs and NRKs, respectively). Conclusion: We report a new LC-MS/MS assay for BK in rat plasma.RIA assay’s results were not reproducible for BK but reliable for ANG II. We found that LKRs has lower BK levels and greater ANG II levels.