부산대학교 도서관

Selectivity for the carboxy-terminus of angiotensin II (Ang II) and the high affinity of antibodies are prerequisites for clinical assays that evaluate Ang II in the presence of Ang I. A high-affinity monoclonal antibody (Kd= 7.1 x 10-11mol/l) was produced and used for the measurement of plasma Ang II. C3H mice were immunized with Ang II coupled by its carboxy-terminus to thyroglobulin. Somatic cell fusion between spleen cells and SP 2/0 myeloma cells, repeated subcloning and re-injection into mice yielded ascites containing sufficient antibody at a 2 x 107-fold dilution. Radioassay standard curves show 50 tracer displacement when 32 fmol unlabelled Ang II is added and 2 fmol Ang II can be detected. Cross-reactivities, taking the reactivity with Ang II as 1.00 are: Ang I 0.003, Ang(1–7) 0.00001, Ang III 1.05, Ang(3–8) 0.88 and Ang(4–8) 0.75. Fast extraction of angiotensin from 2 ml plasma by reversible adsorption to phenylsilylsilica (Bondelut PH) provides recoveries of 96–102. During angiotensin converting enzyme inhibition with 25 mg intravenous captopril, plasma immunoreactive Ang II decreased in supine normal volunteers from 8.6 ± 3.6 to 4.5 ± 3.4 fmol/ml (P< 0.01, n = 8). It thus appears that plasma immunoreactive Ang II can now be measured after a simple extraction procedure by using monoclonal antibodies.