Vasopressin and Renin in High Output Heart Failure of Rats

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Abstract
The hemodynamic effects of vasopressin and the renin-angiotensin system was studied in an animal model of high output heart failure in conscious rats (aorto-acaval fistula). Significantly elevated levels of plasma renin concentration (P < 0.025), norepinephrine (P < 0.02) and up to 4-5 times higher values of vasopressin (P < 0.002) were found in the rats with heart failure as compared with control animals. In contrast to the control rats that had a normally functioning osmoreceptor system, an inverse relationship between plasma osmolality and arginine vasopressin was found in the rats with heart failure in association with edema. Using a specific antagonist of the pressor activity of vasopressin, no significant effect of the heart rate, mean arterial pressure, cardiac output (thermodilution) and peripheral vascular resistance was found in the control animals and in the rats with aorto-caval fistula. Captopril resulted in a significant fall of mean arterial pressure in the rats with shunt (P < 0.001). The coincidence of high values of vasopressin and in a number of animals, low plasma osmolalities and edema suggests a role of vasopressin in the formation of edema and in the development of dilutional hypo-osmolality.