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Clinical Chemistry 45: 659-664, 1999;
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(Clinical Chemistry. 1999;45:659-664.)
© 1999 American Association for Clinical Chemistry, Inc.

Articles

Measurement of Plasma Renin Activity with Use of HPLC-Electrospray-Tandem Mass Spectrometry

Victoria F. Fredline1, Eva M. Kovacs2, Paul J. Taylor2 and Anthony G. Johnson2,a

1 Department of Clinical Pharmacology, Princess Alexandra Hospital, Brisbane, Queensland, Australia 4102.

2 University of Queensland Department of Medicine, Princess Alexandra Hospital, Brisbane, Queensland, Australia 4102.
a Address correspondence to this author at: James Lance Glaxo Wellcome Medicines Research Unit, Parkes 10 East, Prince of Wales Hospital, Randwick, New South Wales, Australia 2031. Fax 61-2-9382 4053; e-mail agj34419{at}glaxowellcome.co.uk

Background: The measurement of renin activity is complicated by difficulties in the quantification of angiotensin 1 (Ang1), the product of the renin-catalyzed reaction. We report an HPLC-electrospray-tandem mass spectrometry (HPLC-ESI-MS/MS) method for the quantification of Ang1 as a measure of plasma renin activity (PRA).

Methods: After incubation (37 °C for 3 or 18 h), samples were prepared using C18 solid-phase extraction. [Val]5Ang1 was used as the internal standard (IS). Chromatography was performed on a C18 column, using 200 mL/L ammonium acetate buffer–800 mL/L methanol as the mobile phase. The flow rate was 150 µL/min, with a chromatographic run time of 5 min/sample. Mass spectrometric detection was in the positive ionization mode with selected reaction monitoring (Ang1 m/z 649.0->784.0; IS m/z 641.9->770.4).

Results: The assay was linear over the range 2.5–500 ng Ang1/mL, which corresponded to a limit of detection (signal-to-noise ratio of 3:1) of PRA of 0.14 ng Ang1 · mL-1 · h-1. The imprecision (CV) of the assay at PRA values of 26.1, 13.5, 3.2, and 0.78 ng Ang1 · mL-1 · h-1 was 7.0%, 7.0%, 15%, and 11%, respectively. Absolute recoveries were 92.3% (Ang1) and 87.4% (IS). Incubation times of 3 h vs 18 h in the PRA assay gave good agreement at PRA <2 ng Ang1 · mL-1 · h-1, but samples with a PRA of 2–5 ng Ang1 · mL-1 · h-1 gave lower PRA results after incubation for 18 h than after 3 h. We compared the HPLC-ESI-MS/MS assay and an RIA for the determination of PRA, with PRA incubation times of 3 h and 1.5 h, respectively. The mean PRA based on RIA of Ang1 was higher than that obtained using HPLC-ESI-MS/MS.

Conclusion: The HPLC-ESI-MS/MS method allows sensitive and specific measurement of PRA. The higher activities measured with the RIA method highlight its potential for overestimation of PRA.© 1999 American Association for Clinical Chemistry




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M. Rauh, M. Groschl, and W. Rascher
Simultaneous Quantification of Ghrelin and Desacyl-Ghrelin by Liquid Chromatography-Tandem Mass Spectrometry in Plasma, Serum, and Cell Supernatants
Clin. Chem., May 1, 2007; 53(5): 902 - 910.
[Abstract] [Full Text] [PDF]


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