Fluorometric determination of angiotensins in human plasma derivatized with 2,3-naphthalenedialdehyde

A fluorometric determination method for angiotensins (ANG I, II, III) in human plasma was developed with 2,3-naphthalenedialdehyde (NDA). Human plasma (10 ml) ultrafiltered with a Molucut L (< M.W. 5000) was put directly on a reversed-phase column for HPLC with an UV detector. The fractions containing each angiotensin were derivatized with 0.1 mM NDA in the presence of cyanide for 60 min at ambient temperature. The derivatized angiotensin (NDA-ANG) was injected onto the HPLC system with a fluorometric detector. Excitation and emission wavelengths were set at 420 nm and 490 nm, respectively. The peak areas of NDA-ANG were linearly related with the amount of angiotensin applied, and were highly reproducible (3.5%, n=5). The concentrations of ANG I, II and III in plasma, calculated from the respective calibration curve, were 315.8 pg/ml, 19.2pg/ml and <1.3pg/ml, respectively. The concentration of ANG II obtained by this fluorometric method coincided with that (22.6 pg/ml) by radioimmunoassay.