Progressive renovascular hypertension by increasing aortic constriction in rats.

Moderate and progressive hypertension was produced experimentally in rats by progressive aortic constriction. The progression of the stenosis was assessed by the differences of pressure across the stenosis. Haemodynamic studies were performed 15, 30 and 60 days after the ligature was placed or after sham operation. Fifteen days after surgery, when the ligated rats did not show any increase in carotic pressure, they showed augmented cardiac output (50.3 +/- 5.4 v. 29.7 +/- 2.0 ml min-1 100 g-1; mean +/- -SEM) and a decreased total peripheral resistance (2.23 +/- 0.21 v. 3.67 +/- 0.20 mmHg ml-1 min 100 g). They also had decreased vascular resistance in both kidneys and in skeletal muscle samples above and below the ligature as well as increased plasma renin content and normal values of plasma volume and extracellular volume. Later in the evolution of hypertension, carotic pressure and the pressure gradient across the stenosis increased (51.8 +/- 4.5 v. 0.9 +/- 1.6 mmHg in controls), cardiac output decreased to control values, total peripheral resistance as well as renal and muscular vascular resistances increased. Plasma and extracellular volume remained unchanged in ligated rats in contrast to controls where they decreased. Perfusion pressure of the kidney below the ligature did never fall below control values (97.2 +/- 3.4 v. 100.4 +/- 2.4 mmHg). A small but constant degree of elastosis and a double layer of myocytes in the renal arterioles above the ligature was the only histological finding.