Role of vasopressin in support of blood pressure in potassium deficient rats

Abstract

Arginine vasopressin (AVP) has been found to contribute to the maintenance of blood pressure (BP) in the rat. Since potassium deficiency results in alterations in systemic hemodynamics, the role of AVP in the control of BP was studied after 14 to 21 days of dietary potassium deficiency. When potassium deficient and control rats were allowed free access to water, plasma osmolality (301.4 +/- 1 vs. 293.4 +/- 3 mOsm/kg; P less than 0.02) and plasma AVP (3.5 +/- 0.2 vs. 2.4 +/- 0.2 pg/ml; P less than 0.02) were increased in potassium deficient animals. To determine the role of this increase in AVP in the maintenance of BP, BP was determined in rats made polydipsic by adding glucose to the drinking water. In both control and potassium deficient rats, increased fluid intake resulted in increased urine output, decreased urinary and plasma osmolality, and a decrease in plasma AVP. While there was no change in BP in control rats when fluid intake was increased, BP fell from 103.9 +/- 1.8 to 96 +/- 2.6 mm Hg (P less than 0.05) in potassium deficient rats with increased fluid intake. To confirm that the decrease in plasma AVP caused the decrease in BP in potassium deficient rats, an AVP pressor antagonist was employed. Following the administration of the AVP pressor antagonist, there was no change in BP in control animals. In contrast, BP fell from 104.3 +/- 1.9 to 98.3 +/- 2.5 mm Hg; P less than 0.05 in potassium deficient rats.(ABSTRACT TRUNCATED AT 250 WORDS)