Angiotensin converting enzyme inhibition prevents the increase in aortic collagen in rats

Four groups of 4-week-old spontaneously hypertensive rats were treated during 4 months with the angiotensin converting enzyme inhibitor quinapril at 1 mg/kg per day (Q1) or 10 mg/kg per day (Q10), hydralazine at 15 mg/kg per day (H), or placebo (P). In the first set of experiments, blood pressure was measured in conscious rats, and plasma and aortic angiotensin converting enzyme activities were evaluated. In the second set of experiments, histomorphometric parameters of the thoracic aorta were evaluated. Mean blood pressure was lower in the Q10 and H groups (136 +/- 16 and 149 +/- 11 mm Hg) compared with the P group (190 +/- 23 mm Hg) (P < .01). The Q1 group showed mean blood pressure values (171 +/- 15 mm Hg) lower than the P group (P < .05) but significantly higher than the Q10 and H groups (P < .01 and P < .05, respectively). Aortic medial cross-sectional area was significantly lower in the H and Q10 groups (455 +/- 61 and 487 +/- 57 x 10(3) microns 2) than in the P group (636 +/- 72 x 10(3) microns 2) (P < .001).(ABSTRACT TRUNCATED AT 250 WORDS)