Mesenteric vascular angiotensin-converting enzyme is increased in experimental diabetes mellitus

1. Diabetes mellitus was induced by streptozotocin in male Wistar rats, and angiotensin-converting enzyme measured in plasma and mesenteric vessels 3 weeks later. 2. Diabetes was associated with increased mesenteric wet weight/bodyweight ratio (control 0.2 s.e.m. 0.02 mg/g, n = 21, vs diabetes 1.0 s.e.m. 0.3 mg/g, n = 27, P less than 0.01, ANOVA). 3. Plasma angiotensin-converting enzyme activity was increased in diabetic rats (98 s.e.m. 3 nmol HL/mL per min) compared with controls (64 s.e.m. 6 nmol HL/mL per min, P less than 0.01, ANOVA). 4. Mesenteric vessel angiotensin-converting enzyme was increased in diabetes mellitus estimated by radioligand binding site density (fmol/mg protein; 1407 s.e.m. 166 fmol/mg protein) compared with controls (890 s.e.m. 56 fmol/mg protein, P less than 0.05, ANOVA) and by enzyme kinetic assay (diabetes, 15.5 s.e.m. 1.5 nmol HL/mg protein per min, controls, 8.3 s.e.m. 0.7 nmol HL/mg protein per min, P less than 0.01, ANOVA). The equilibrium dissociation constant of ligand-angiotensin-converting enzyme interaction was unchanged. 5. Increased vascular angiotensin-converting enzyme concentration may contribute to vascular hypertrophy and diabetic vasculopathy by increased local synthesis of angiotensin II.