The role of vasopressin in blood pressure regulation immediately following acute haemorrhage in the rat

Abstract

The possible pressor effect of vasopressin immediately after acute hemorrhage was studied using anesthetized Brattleboro rats with diabetes insipidus and rats of the Long Evans parent strain. A blood loss of 0.5% of the body weight caused a significant decrease in mean arterial blood pressure, measured 10 min later, in Brattleboro rats, whereas this degree of hemorrhage was non-hypotensive in the control Long Evans rats. Following subsequent blood losses (each of 0.5% of the body weight), mean arterial blood pressure in Brattleboro rats was always significantly lower than in Long Evans rats. While no antidiuretic activity was at any time found in the plasma of Brattleboro rats, hemorrhages greater than 1% of the body weight were associated with marked increases in plasma Arg vasopressin (AVP) of Long Evans rats. When Brattleboro and Long Evans rats were subjected to a single hemorrhage of 2% of the body weight, the immediate decrease in arterial blood pressure was similar in the 2 groups. However, 5 and 10 min after the hemorrhage the arterial blood pressure was significantly higher in the Long Evans rats. When vasopressin was infused into Brattleboro rats so that plasma levels of the hormone approached those found in Long Evans rats, the mean arterial blood pressure 0, 5 and 10 min after hemorrhage was similar to that in the Long Evans animals. In the anesthetized rat, vasopressin plays an important role in the regulation of arterial blood pressure during the period immediately following acute hemorrhage.