The pathogenesis of hypertension induced by renal constriction.

Blood pressures were determined on forty-two young male albino rats and a basal level established. The rats were then divided into four groups and subjected to one of the following operations: (a) unilateral nephrectomy with exposure and handling of the opposite kidney; (b) unilateral nephrectomy and constriction of the remaining kidney with a silk figure-of-eight ligature; (c) unilateral renal constriction with a silk figure-of-eight ligature, the other kidney being left intact after exposure and handling; (d) unilateral nephrectomy and removal of the poles of the contralateral kidney (three-quarters nephrectomy). The animals were followed for 50 days, during which blood pressures were measured on twenty occasions, then killed by exsanguination under ether anesthesia. The organs were weighed according to a standardized procedure and studied histologically. Individual determinations of serum creatinine and of the hematocrit levels were made. Mean lines and frequency distributions of blood pressure were subjected to statistical analysis. A definitely significant increase in blood pressure developed in the group subjected to operation (b) within 4 days postoperative. In none of the other groups did hypertension develop. Analysis of the individual renal weights and creatinine levels indicates the independence of the development of hypertension from the total mass of functioning renal tissue. Nor is it dependent on the prevention of renal hypertrophy or the presence of fibrous perinephritis. The effect is probably due to the production of a disturbance of hemodynamics or tissue tension with the liberation of a pressor substance by the injured kidney.