Hemodynamic effects of long-term converting-enzyme inhibition in renal hypertensive rats.

The hemodynamic effects of a converting-enzyme inhibitor (CEI) given during 12 consecutive hours were studied in severe chronic renal hypertensive and normotensive Wistar rats. Hemodynamic parameters were obtained by thermodilution method in conscious unrestrained animals twenty-four hours after surgery. A bolus of CEI induced a significant decrease of mean arterial pressure (MAP) (from 192.2 +/- 8.2 to 163.3 +/- 5.9 mmHg, p less than 0.001) and total peripheral resistance (TPR) (from 7.69 +/- 0.53 to 5.83 +/- 0.33 mmHg.min/ml 100 g) in hypertensive animals. Cardiac index (CI) and heart rate increased significantly (p less than 0.05). Infusion of CEI to hypertensive animals during 12 consecutive hours produced a further progressive decrease in MAP and TPR (p less than 0.05) and an increase in CI (p less than 0.05). Heart rate did not change. Acute and prolonged infusions of CEI to normotensive group induced less but similar effect to those observed in hypertensive group. These results suggest that an increase of the renin-angiotensin system activity is the principal mechanism involved in the maintenance of high blood pressure during chronic phase of renal hypertension on the rats.