Interaction of Radioinsulin with Serum Proteinsin Vitroand with Liverin VivoAmong Diabetic and Nondiabetic Patients

Abstract

Studies were carried out in vivo and in vitro in order to evaluate the behavior of insulin in nondiabetic subjects and in insulin-responsive and insulin-resistant diabetic patients. Insulin-binding proteins were characterized by means of reverse flow zone electrophoresis of serum containing insulin-I¹³¹ on Whatman No. 3 filter paper in barbital buffer, pH 8.6. Insulin-I¹³¹ alone remained at the origin, but radioinsulin in serum from normal subjects, and from non-insulin-treated and insulin-responsive diabetic patients, migrated with a mobility that corresponded to the zones of the alpha and beta globulins. However, insulin-I¹³¹ in serum from insulinresistant diabetic patients moved in sociation with the gamma or inter-gamma-beta globulins. After treatment with corticosteroids, 2 of 3 resistant diabetic patients exhibited significant reductions in insulin requirement and changes in the electrophoretic patterns which then resembled those of the responsive diabetic patients. In addition to the unique Protein-insulin-I¹³¹ complexes, the insulin-resistant patients also demonstrated delays in uptake and in release of insulin-I¹³¹ radioactivity by the liver in vivo and enhanced insulin-binding capacity of the serum in vitro.