Comparison of Insulin Binding to Cells of Fed and Fasted Obese Patients: Results in Erythrocytes and Monocytes*

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Abstract
The erythrocyte (RBC) has received recent interest as a cell model to examine insulin receptor status in humans. In the present study we have compared the insulin receptors on mature RBCs and monocytes of four hyperinsulinemic obese patients in the fed state and after a 14-day fast (s and monocytes increased significantly in each patient. Maximal binding of [125]]odoinsulin to RBCs increased by 29% (range, 20-46%), and binding to monocytes increased by 116% (range, 46–312%).In response to the fast, the concentration of insulin needed to inhibit binding by 50% decreased from 5 to 2 ng/ml in RBC and from 3 to 1 ng/ ml in monocytes, indicating an increase in receptor affinity in both RBCs and monocytes. Conventional and computer-fitted Scatchard analyses demonstrated no change in the receptor concentration of RBCs of any patient, whereas the receptor concentration of monocytes increased by more than 50% in two of the four patients and by 40% for the group. Thus, in response to the fast, the direction of the change in insulin binding was similar in the RBCs and monocytes, whereas the magnitude and, in certain patients, the mechanism of the binding increase differed.(J Clin Endocrinol Metab54: 40, 1982)