A sensitive, rapid radioimmunoassay for angiotensin II

A rapid but sensitive radioimmunoassay for the measurement of plasma angiotensin II has been developed. Antiserum to angiotensin II coupled to albumin was raised and boosted by subsequent injections of unconjugated hormone. The antibody was found to react equally with the Val5 and Ileu5 forms of angiotensin II as well as with the hexa and heptapeptide fragments. Only minor cross reactivity with angiotensin I was observed. The minimum amount of angiotensin II that could be reliably measured was 4pg per tube. Because plasma incubates resulted in large and variable losses in sensitivity, an ethanol precipitation step was employed for plasma samples prior to radioimmunoassay. The normal range of venous angiotensin II levels in ambulant volunteers was 20-83pg/ml. Highly significant correlations of plasma angiotensin II with simultaneously drawn samples for renin determination were noted. Venous angiotensin II levels in a number of clinical situations are documented.