The Insulin-carrying Protein of Normal Human Serum

Abstract

Direct evidence that insulin is bound to serum protein has been obtained by electrophoresis of insulin 1-131 in serum with agar as the supporting medium. It was shown that immunologically active insulin I-131 was incorporated in a precipitin reaction between alpha-one globulin and its specific antibody. This alpha-one globulin has been called the insulin-carrying protein to distinguish it from the acquired insulin-binding globulin found in patients previously treated with insulin. The insulin-carrying protein is presumed to participate in an insulin-buffer system by which insulin supply to peripheral tissues is sustained under normal conditions. In diabetic patients with a high binding capacity of the acquired insulin-binding globulin, the insulin-carrying protein is depleted of insulin. Since such patients have a poor response to exogenous insulin, the association of insulin with the insulin-carrying protein may be necessary for the clinical control of diabetes.