Effect of norepinephrine infusion on plasma vasopressin levels in normal human subjects.

Norepinephrine was continuously infused for 30 minutes at a rate of 0.2 and 0.3 mug/kg/min into 3 normal human subjects, and plasma vasopressin levels, plasma osmolality, hematocrit value, blood pressure, and heart rate were determined simultaneously. In norepinephrine infusion, an elevation of mean blood pressure and a decrease in heart rate was seen, and the degree of these changes was greater with the infusion at a rate of 0.3 mug/kg/min. Plasma vasopressin levels were suppressed by the infusion, and a dose-response relationship was recognized between the infusion at rates of 0.2 mug/kg/min and 0.3 mug/kg/min, while plasma osmolality did not change, and the hematocrit value rose slightly. These results suggest that norepinephrine-induced water diuresis is related to the suppression of the vasopressin release.