The Effect of Quantitative Reduction of Renal Blood Flow Upon the Pregnant Rabbit

Abstract

In a recent paper (1) we described a syndrome which occurred in pregnant dogs and rabbits subjected to renal ischemia and which was characterized by hypertension, albuminuria, coma, convulsions, and death. In most of the animals uremia and hematuria were also noted, but these were not constant findings. Cardiac dilatation with acute congestion of all organs, and necroses in the liver, myocardium, and kidneys were the usual findings at autopsy.Bilateral constriction of the renal arteries rendered estimation of the actual renal flow so difficult that only very gross variations could be appreciated, and varying amounts of renal damage and nitrogen retention complicated the picture. A more precise quantitative method was needed in order to subject the animals to comparable amounts of renal ischemia. Rytand (2) described the production of renal ischemia by reducing the blood flow through the aorta proximal to the points of origin of the renal arteries. It seemed that the utilization of this method with the application of a clamp of known diameter to the previously measured aorta should give a fairly accurate estimation of the relative reduction of blood flow through the kidneys. METHODSix pregnant and eight non-pregnant female rabbits of 8 pounds or more in weight and of varying breeds were used as the experimental animals in which to constrict the aorta proximal to the points of origin of the renal vessels and four pregnant animals of the same type were used to control the effect of simple aortic constriction by placing the clamp distal to the points of origin of these arteries. These animals were obtained from a local dealer and were observed for three weeks before the experiment was begun.For an additional period of three weeks blood pressure was recorded three times weekly by an indirect method (3).Urine was collected in metabolism cages and examined weekly. Specific gravity was determined by a calibrated urinometer; albumin was tested qualitatively by the heat and acetic acid test, and careful microscopic examinations were done on the urine after it had been centrifuged at low speed. Measurements of the cell volume, red blood cells, and hemoglobin were done weekly. Studies of the cell volume were done by the Wintrobe (4) method; the red blood cells were counted in chambers, using pipettes approved by the Bureau of Standards; and hemoglobin estimations were made by the Sahli technic.Chemical measurements of the blood were made at weekly intervals. Measurements of the non-protein nitrogen were done by the method of Folin and Wu (5); of urea by the method of Van Slyke and Cullen (6); and of uric acid by the Folin (7) technic. Cholesterol was determined by the method of Leiboff (8), chlorides by the Whitehorn (9) method, and the carbon dioxide combining power by the method of Van Slyke (10).Following the period of three weeks during which control studies were made the animals were subjected to laparotomy under aseptic technic. The aorta, which had been measured at laparotomy, was constricted above or below the point...