Octapeptide-Specific and Sensitive Assay for Angiotensin II in Plasma |
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Authors: | Jürg Nussberger Dorette B Brunner Bernard Waeber Hans R Brunner |
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Institution: | Centre Hospitalier Universitaire, Division of Nephrology and Hypertension , Lausanne, Switzerland |
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Abstract: | Abstract Angiotensin-(1–8)octapeptide (angiotensin II) is the active principle of the reninangiotensin system. Crossreaction of angiotensin II-antisera with inactive precursors and metabolic fragments prevented the specific quantitation of this hormone in biological fluids. Peptide-extraction on bonded-phase silica followed by peptide-separation using isocratic reverse-phase high performance liquid chromatography and subsequent radioimmunoassay rendered possible the octapeptide-specific measurement of angiotensin II in 2 ml plasma with a detection limit of 0.4fmol/ml. The coefficient of variation for intra-assay precision was 0.06 and for inter-assay precision 0.13. 125Iangiotensin II was recovered from plasma by solid-phase extraction to 99±2% (mean ± S.D.). The overall recovery of 5, 10 and 20 fmol unlabeled angiotensin II added to plasma was 80±10%. Plasma concentrations in supine normal humans averaged 4.1 ± 1.6 fmol/ml and were suppressed below the detection limit by angiotensin I converting enzyme inhibition. |
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Keywords: | Solid-phase peptide extraction high performance liquid chromatography radioimmunoassay angiotensin metabolites sensitivity |
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