Effect of bilateral nephrectomy on hypertension produced by acute aortic coarctation

1. The hemodynamic responses to acute (45 min) aortic coarctation were studied in conscious intact (N = 7) or bilaterally nephrectomized (N = 7) Wistar rats (250-320 g). The degree of constriction of the aorta was monitored by reducing aortic flow (measured with a pulsed Doppler flowmeter) to 40% of the basal level. 2. The nephrectomized rats presented a smaller (P < 0.05) increase in carotid pressure (14-17%) than the intact rats (25-36%). Although the aortic constriction reduced significantly the aortic flow to 40% of the basal level in both groups of rats, the calculated change in aortic resistance imposed by coarctation in the intact group was significantly (P < 0.05) higher (167-292%) than that observed (173-183%) in the nephrectomized group, except 5 min after coarctation. 3. The hemodynamic data obtained in the present study confirm our findings that nephrectomized rats display a blunted hypertensive response to acute aortic coarctation which is attributed mainly to the mechanical effect of constriction. In addition, the present data indicate that the release of vasopressor substances triggered by the kidneys in intact subjects are responsible for the gradual increase in aortic resistance during coarctation.