[Metabolism of angiotensin II during angiotensin infusion and following sodium depletion].

1. Angiotensin II (A II) and angiotensin (3--8)-hexapeptide (H) were measured by radioimmunoassay in arterial and venous plasma before and during infusion of angiotensin II-amide in five normotensive subjects, both in sodium-replete and sodium-depleted states. The separation of the oligopeptides was performed by thin layer chromatography. 2. Before sodium-depletion the mean ratio of arterial to venous A II was 1.14+/-0.11:1, corresponding to an A II-extraction of approximately 12% during a single forearm passage. Infusion of A II-amide increased extraction of A II. The mean ratio of arterial to venous A II increased to 1.68+/-0.3:1, corresponding to an extraction of approximately 39% when 8 ng-min-1-kg-1 were infused. 3. Sodium depletion increased arterial and venous concentrations of A II and H. During infusion of angiotensin II-amide the arterial and venous concentrations of A II and H increased approximately parallel to the concentrations before sodium depletion. The extraction of A II did not differ significantly in both states. 4. The augmented extraction extraction of A II observed during infusion of angiotensin II-amide suggest an overproportional increase of the metabolism of A II under the latter condition. Sodium depletion, however, does not appear to cause a percent change in A II metabolism.