Origin of angiotensin in human leukocytes

The capability of human leukocytes to synthesize angiotensin peptides was studied. Leukocytes which were prepared from heparinized blood by sedimentation in dextran were incubated for 0, 1, 2, 4, 6, 8, and 24 h at 37 degrees C with the 3H-labeled amino acid isoleucine. At the various time points the washed cells were extracted with 0.1 M acetic acid. The extracts contained radioactive material which eluted from a Bio Sil TSK 125 gel filtration column in the low-molecular-weight range with the same retention time as synthetic angiotensin I (ANG I) or angiotensin II (ANG II). The extracted radioactive material also bound to anti-ANG I and anti-ANG II antibodies. However, excess of unlabeled synthetic ANG I or ANG II failed to displace the bound radioactivity. Rechromatography of the radioactive material which eluted in the low molecular weight fractions of the gel filtration column could be characterized as non-incorporated 3H-isoleucine on a reversed phase C18 column with an acetonitrile gradient. These findings demonstrate the lack of an angiotensin-generating pathway in human leukocytes. Further studies are necessary to determine the origin of angiotensin peptides in human leukocytes.