Arterial-venous determinations of the "immunoreactive" angiotensin peptides in human subjects

Simultaneous measurements of arterial and venous plasma "immunoreactive" angiotensin II and angiotensin II peptide fragments (octapeptide, heptapeptide, hexapeptide, and pentapeptide), done with high performance liquid chromatography and radioimmunoassay, were obtained in nine human subjects. Results indicate that the angiotensin II octapeptide is the major peptide fragment in both arterial and venous plasma. Approximately 80% of the "immunoreactive" angiotensin II measured in both arterial and venous plasma is the angiotensin II octapeptide fragment. The concentration of angiotensin II octapeptide in venous blood approximated the concentration of angiotensin II octapeptide measured in arterial blood. These data suggest that venous concentrations of angiotensin II octapeptide probably reflect the activity of the tissue renin angiotensin system, because its concentration was much higher than would be predicted from inactivation of arterial blood angiotensin II octapeptide in peripheral tissues.