Analysis of the Cardiovascular Effects of Arginine Vasopressin in Conscious Dogs

SUMMARY The effects of physiological elevations in arginine vasopressin on the cardiovascular system were studied in a group of nine conscious, chronically instrumented dogs. The animals were studied under normal conditions (plasma vasopressin, 4.1 ± 0.4 pg/ml), after 24 hours of dehydration (plasma vasopressin, 7.3 ±1.5 pg/ml), after a 30-minute vasopressin infusion at 2.6 ng/kg/min (plas-ma vasopressin, 62.8 ± 10.3 pg/ml), and after a 4-day vasopressin infusion at 2.6 ng/kg/min (plasma vasopressin, 96.6 ±8.1 pg/ml). These increases in vasopressin concentration resulted in no change in arterial pressure and significant changes in the following: a 13 and 29 % decrease in resting cardiac output during dehydration and acute infusion, respectively; a 26 % reduction in heart rate during acute infusion; a 12 and 54 % increase in total peripheral resistance during dehydration and acute infusion; a 16 and 22 % reduction in mean circulatory filling pressure during dehydration and chronic vasopressin infusion. In addition, maximum pumping ability of the heart was reduced 16 and 31 % during dehydration and acute infusion, respectively. These data suggest that elevations of vasopressin such as those occurring during dehydration or volume depletion potentially may affect cardiovascular performance by three mechanisms: 1) greatly increasing resistance to flow, 2) reducing heart rate, 3) suppressing the pumping ability of the heart. (Hypertension 9: 371-378, 1987