Plasma concentrations of angiotensin metabolites in young male normotensive and mild hypertensive subjects.

The plasma concentrations of angiotensin (Ang) I, Ang II, and their metabolites (Ang (3-8), (4-8), (5-8), and (3-4)) following in vitro ACE inhibitory activity were examined in young male normotensive (NT) (n = 7), and mild hypertensive (HT) volunteers (n = 6). There were no differences in supine plasma levels of Ang I, Ang II, and Ang (5-8) between the NT and HT groups: Ang I, 304 +/- 43 fmol/ml vs. 293 +/- 15 fmol/ml; Ang II, 32 +/- 6 fmol/ml vs. 43 +/- 10 fmol/ml; Ang (5-8), 176 +/- 22 fmol/ml vs. 133 +/- 32 fmol/ml. In addition, there were no significant differences between groups in any of these Ang levels when measured after standing for 60 min. However, the HT group showed significantly reduced supine and upright plasma Ang (3-8) and Ang (3-4) levels as compared to the NT group. In particular, the supine plasma level of Ang (3-4) (71 +/- 13 fmol/ml-plasma) in the HT group was significantly (1/3-fold) lower than that in the NT group (197 +/- 35 fmol/ml-plasma). An inverse correlation between the plasma level of Ang (3-4) and the upright systolic blood pressure (r = -0.627, p < 0.02, n = 13) was observed, indicating that the metabolism of Ang (3-4) might have been associated with the change in blood pressure.