Serum angiotensin-converting enzyme activity and active renin plasma concentrations in insulin-dependent diabetes mellitus.

We report here the alterations of serum angiotensin-converting enzyme activity (S-ACE) and of active renin plasma concentrations (ARPC) in 41 insulin-dependent diabetes mellitus (IDDM) patients compared with those of 26 control subjects. The IDDM patients had S-ACE activity (54 +/- 16 I.E.) in the upper normal range (controls, 39 +/- 7). When the patients were subclassified according to their diabetic complications, a significant increase of S-ACE within the IDDM group compared to the controls was observed in patients with nephropathy (68 +/- 13, P less than 0.001) with persistent proteinuria and with retinopathy (63 +/- 14, P less than 0.001). A significant correlation was found between proteinuria and S-ACE (r = 0.98, P less than 0.001) and between retinopathy and S-ACE levels (r = 64, P less than 0.001). No correlation between blood pressure and S-ACE or between blood glucose and S-ACE was observed. The ARPC were within the normal range in the IDDM (21 +/- 9 ng/l) and in control (19 +/- 3) groups. No correlations between ARPC and blood pressure or blood glucose or the degree of diabetic complications were registered. These data show that S-ACE activity is elevated in IDDM patients with nephropathy-proteinuria and/or with retinopathy and the circulating renin may not represent the renal renin-angiotensin vascular system.