Measurement and characterization of angiotensin peptides in plasma.
We report a method for the extraction of angiotensin peptides from plasma with a mixture of acetone, 1 mol/L HCl, and water (40/1/5 by vol). The method is highly reproducible for the measurement of angiotensin I and angiotensin II in small sample volumes, with analytical recoveries of about 80% for both peptides. We investigated the influence of sample handling and found a standard procedure for blood collection, plasma preparation, and extraction was essential. The method was used to measure angiotensin I and II in rat and human plasma. In rat plasma, the mean (+/- SEM) concentrations of angiotensin I and angiotensin II were determined to be 67 (+/- 8) and 14 (+/- 1) pmol/L (n = 10), respectively. Neither angiotensin I nor angiotensin II was detectable 24 h after bilateral nephrectomy. Acute oral administration of the converting-enzyme inhibitor ramipril caused a significant increase of angiotensin I from 85 (+/- 6) to 257 (+/- 33) pmol/L (n = 10; P less than 0.001) and a significant decrease of angiotensin II from 12 (+/- 1) to 7 (+/- 0.4) pmol/L in rat plasma (n = 9; P less than 0.001). In human plasma, angiotensin I and angiotensin II values of 21 (+/- 1) and 6.6 (+/- 0.5) pmol/L (n = 10) were found. A single oral dose of the diuretic furosemide increased angiotensin I significantly from 21 (+/- 1) to 32 (+/- 1.7) pmol/L (n = 5); P less than 0.001), whereas angiotensin II remained unchanged, 6.6 (+/- 0.5) vs 6.4 (+/- 0.4) pmol/L (n = 5). Extracted peptides could be identified as [IIe5]-angiotensin I and [IIe5]-angiotensin II by HPLC in combination with specific radioimmunoassays for angiotensin I and angiotensin II.
Hermann
K
K
Department of Pharmacology, University of Heidelberg, F.R.G.
Ganten
D
D
Unger
T
T
Bayer
C
C
Lang
R E
RE
D000328:Adult; D000803:Angiotensin I / Q000031:analogs & derivatives / Q000097:blood*; D000804:Angiotensin II / Q000031:analogs & derivatives / Q000097:blood*; D000818:Animals; D001800:Blood Specimen Collection; D001643:Bridged Bicyclo Compounds / Q000494:pharmacology; D002851:Chromatography, High Pressure Liquid; D005260:Female; D006801:Humans; D007457:Iodine Radioisotopes; D008297:Male; D009392:Nephrectomy; D011863:Radioimmunoassay; D017257:Ramipril; D051381:Rats; D012016:Reference Values
D001643:Bridged Bicyclo Compounds; D007457:Iodine Radioisotopes; D000804:Angiotensin II; D000803:Angiotensin I; C046239:angiotensin I, Ile(5)-; D017257:Ramipril