THE EFFECT OF DIFFERENT DEGREES OF SUBDIAPHRAGMATIC AORTIC CONSTRICTION ON HEART WEIGHT AND BLOOD PRESSURE OF NORMAL AND HYPOPHYSECTOMIZED RATS

The aortae of groups of normal and hypophysectomized rats were constricted with rings of five different sizes (0.93, 0.83, 0. 74, 0.71, and 0.63 mm. diameter). In normal rats constriction caused an increase in heart weight and blood pressure which was the greater the narrower the constriction. If constriction exceeded 0.74 mm., cardiac hypertrophy reached extremely high values, while the blood pressure was lower than in groups with less constriction. The blood pressure response to Adrenalin or Infundin increased in proportion to the degree of constriction down to 0.74 mm.; greater constriction reduced the response. In hypophysectomized rats no degree of aortic constriction produced hypertension or cardiac hypertrophy, yet the increase in blood pressure after Adrenalin or Infundin was as great as in the normal intact rats.