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 flow meter) to 40% of the basal level. 2. The nephrectomized rats presented a smaller (P<0.05) increase in carotid pressure (14-17%) than the int act rats (25-36%). Although the aortic constriction reduced significan tly the aortic flow to 40% of the basal level in both groups of rats, the calculated change in aortic resistance imposed by coarctation in t he intact group was significantly (P<0.05) higher (167-292%) than that observed (173-183%) in the nephrectomized group, except 5 min after c oarctation. 3. The hemodynamic data obtained in the present study conf irm our findings that nephrectomized rats display a blunted hypertensi ve response to acute aortic coarctation which is attributed mainly to the mechanical effect of constriction. In addition, the present data i ndicate that the release of vasopressor substances triggered by the ki dneys in intact subjects are responsible for the gradual increase in a ortic resistance during coarctation.