Immunoassay of plasma vasopressin in man.

A radioimmunoassay for arginine vasopressin has been developed that is sensitive to the hormone at 1 pg/ml. When plasma was filtered on G-25 Sephadex, immunoreactivity was detected in three regions. Endogenous arginine vasopressin was the third and smallest of the peaks and was recovered just after the salt. By combining gel filtration with immunoassay, we have made precise measurements of arginine vasopressin in a few milliliters of plasma.