Influence of lower body negative pressure upon arginine vasopressin release

Lower body negative pressure (9-12 kPa) was applied to ten normal subjects. Large increases in plasma arginine vasopression concentration occurred only in subjects that experienced syncopal symptoms and developed hypotension. Blood samples obtained from the superior vena cava at 1/2 min intervals during application of negative pressure showed that maximal plasma vasopressin concentrations occurred with hypotension. Chromatography of the presyncopal plasma on Sephadex G-25 gave a large peak which eluted in the position of synthetic arginine vasopressin.