Effects of Increases in Plasma Vasopressin Concentration on Plasma Renin Activity, Blood Pressure, Heart Rate, and Plasma Corticosteroid Concentration in Conscious Dogs*

Abstract

It is known that vasopressin decreases PRA and heart rate and increases blood pressure and plasma corticosteroid concentration. The purpose of this study was to determine the plasma concentration of vasopressin required to produce these effects. Arginine vasopressin was administered iv to five normal conscious dogs as priming injections of 0.1, 0.5, 1.0, 2.5, 5.0, and 10.0 ng/kg, followed by infusions of 0.01, 0.05, 0.1, 0.25, 0.5, and 1.0 ng/kg -min, respectively, for 30 min. These doses produced increases in the plasma vasopressin concentration (±SE) of. 1.0 ± 0.8, 2.1 ± 0.3, 4.3 ± 1.8, 11.4 ± 1.0, 19.7 ± 6.4, and 30.8 ± 7.8 pg/ml, respectively, from a basal level of 2.7 ± 0.2 pg/ml. An increase in the plasma vasopressin concentration of 2.1 ± 0.3 pg/ml suppressed PRA by 19 ± 5% (P < 0.02); increases of 4.2 ± 1.8 pg/ml or more suppressed PRA by 34 ± 12% (P < 0.005). Only the highest dose of vasopressin produced a significant pressor effect (9 ± 3 mm Hg; P < 0.05) or lowered the heart rate (18 ± 4 beats/min; P < 0.005). An increase in plasma vasopressin concentration of 19.7 ± 6.4 pg/ml was required to increase the plasma corticosteroid concentration (1.2 ± 0.2 to 2.2 ± 0.4 μg/dl; P < 0.01); the largest dose of vasopressin increased the plasma corticosteroid concentration from 1.5 ± 0.1 to 2.4 ± 0.6 μg/dl (P < 0.02). Twenty-four-hour water deprivation in the same dogs increased the plasma vasopressin concentration from 2.5 ± 0.2 to 7.4 ± 0.6 pg/ml (P < 0.01). Nonhypotensive hemorrhage in another group of dogs increased the plasma vasopressin concentration from 2.5 ± 0.2 to 47.4 ± 16.8 pg/ml (P < 0.05). These data indicate that elevations in the plasma vasopressin concentration within the range observed during 24 h of water deprivation and nonhypotensive hemorrhage produced significant decreases in renin secretion and heart rate and elevations in blood pressure and corticosteroid secretion.