Studies on the State of Insulin in Blood: Properties of Circulating “Free” and “Bound” Insulin

Abstract
Studies are presented on the immunologic reactivity, electrophoretic mobility on Pevikon and chromatographic behavior on Sephadex of the 2 forms of insulin in human blood. The “free” form of insulin corresponds in its physicochemical, immunologic and biological properties to crystalline insulin. The “bound” form of insulin exhibits a higher molecular weight, slower electrophoretic mobility and diminished reactivity with insulin antisera. Acid ethanol extraction increases the reactivity of “bound” insulin with insulin antisera, the antisera inhibiting the biological activity of acid ethanol extracts of “bound” insulin on isolated epididymal adipose tissue. (Endocrinology76: 709, 1965)