Conversion of angiotensin I to angiotensin II in sheep

1. The methodology for measurement of angiotensin I in whole blood is described. 2. Angiotensin I was measured in arterial and venous blood samples from sodium-loaded, sodium-replete and sodium-depleted sheep. Venous blood concentrations were higher than arterial angiotensin I concentrations. Arterial angiotensin I concentrations increased with increasing sodium deficiency. 3. Angiotensin II was infused into six sodium-replete sheep, the blood concentrations of angiotensin II measured and the metabolic clearance rates calculated. The average value was 121 +/- 21 1/h. 4. Angiotensin I was then infused into these sheep and arterial and venous blood concentrations of angiotensins I and II determined. From this data and the metabolic clearance rate of angiotensin II, the degree of conversion of angiotensin I to II was calculated. The values varied in different sheep from 54 +/- 2% to 105 +/- 6% (n = 6).