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 H-3-labeled amino acid isoleucine. At the va rious time points the washed cells were extracted with 0.1 M acetic ac id. The extracts contained radioactive material which eluted from a Bi o Sil TSK 125 gel filtration column in the low-molecular-weight range with the same retention time as synthetic angiotensin 1 (ANG I) or ang iotensin II (ANG II). The extracted radioactive material also bound to anti-ANG I and anti-ANG II antibodies. However, excess of unlabeled s ynthetic ANG I or ANG II failed to displace the bound radioactivity. R echromatography of the radioactive material which eluted in the low mo lecular weight fractions of the gel filtration column could be charact erized as non-incorporated H-3-isoleucine on a reversed phase C-18 col umn with an acetonitrile gradient. These findings demonstrate the lack of an angiotensin-generating pathway in human leukocytes. Further stu dies are necessary to determine the origin of angiotensin peptides in human leukocytes.