Angiotensin II and its heptapeptide (2-8), hexapeptide (3-8), and pentapeptide (4-8) metabolites in arterial and venous blood of man.
We made separate measurements of angiotensin II (A II) and of its immunoreactive metabolites (2-8 heptapeptide, 3-8 hexapeptide, and 4-8 pentapeptide) in arterial and venous plasma from subjects with widely different plasma levels of the peptides. A II and its three metabolites were extracted from blood, separated by paper chromatography, and measured by radioimmunoassay using an A II antiserum which had a 100% cross-reaction with each metabolite. In contrast to results of previous studies, A II was found to predominate in both arterial (60-100%) and venous (55-100%) blood. The biologically active 2-8 heptapeptide metabolite accounted for only 10% of the activity in arterial plasma. Radioimmunoassay of venous plasma extracts using an A II antiserum which had a low cross-reaction with the 3-8 hexapeptide and the 4-8 pentapeptide confirmed the results obtained using the antiserum which had a 100% cross-reaction with the metabolites. We conclude that radioimmunoassay methods for measuring A II in venous blood may be more accurate and relevant than has previously been recognized. The small difference between A II concentrations in arterial and venous plasma suggests further that there may be significant conversion of angiotensin I (A I) to A II in the limb vasculature.
D000328:Adult; D000368:Aged; D000595:Amino Acid Sequence; D000804:Angiotensin II / Q000031:analogs & derivatives / Q000097:blood* / Q000302:isolation & purification; D001158:Arteries; D002854:Chromatography, Paper; D005260:Female; D006207:Half-Life; D006493:Heparin / Q000494:pharmacology; D006801:Humans; D006868:Hydrolysis; D008297:Male; D008875:Middle Aged; D010455:Peptides / Q000097:blood* / Q000302:isolation & purification; D011247:Pregnancy; D011863:Radioimmunoassay; D012083:Renin / Q000097:blood; D014680:Veins
D010455:Peptides; D000804:Angiotensin II; D006493:Heparin; D012083:Renin