Development of a Strain of Spontaneously Hypertensive Rabbits.

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Abstract
The possibility of a controlled study of the inheritance of hypertension was presented when it was noted that occasional stock rabbits had elevated pressures, i.e., spontaneous hypertension. Out of 553 animals screened, 2.7% were found to have systolic pressures of 160 mm Hg or more on 2 separate occasions and these were selected for breeding stock. The offspring were raised in a special rabbitry so that environmental conditions were kept standard. Blood pressures were determined from the abdominal aorta with a sphygmomanometer cuff and the average of 4 or 5 systolic and diastolic readings was recorded. Blood pressure readings were obtained at 3-4 months of age (4-5 lb. weight) and as often as once or twice a month thereafter to 8 months of age. The highest systolic pressure readings were compiled for 3 age groups. At 3-4 months of age the mean systolic pressure for 96 rabbits was 145 mm Hg; 32% had pressures of 150-185 mm Hg. At 5-6 months of age the mean systolic pressure for 62 animals was 155 mm Hg; 54% had pressures of 150-185. At 7-8 months mean systolic pressure for 52 rabbits was 160 mm Hg; 73% had pressures of 150-185. The mean systolic pressures at 5-6 and 7-8 months of 155 and 160 mm Hg, respectively, were each statistically significant when compared to the mean of 145 mm Hg at 3-4 months of age. Mean systolic pressures were not significantly different between sexes in any of the 3 age groups. There was no correlation between body weight and systolic pressure in any single age group. Normal rabbits at 4 months of age have systolic pressures averaging 135 mm Hg with an average increase of 10 mm Hg by 12 months. It was concluded that there is an hereditary factor in rabbit hypertension. The similarity between characteristic changes of blood pressure in spontaneously hypertensive animals and in the normal rabbit population was discussed.