Studies of insulin binding in children using human erythrocytes in small amounts of blood

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Abstract
We have demonstrated specific insulin binding by the erythrocytes (RBCs) of children. Complete binding studies were done using as little as 5 ml of blood. The receptors exhibited competition-inhibition curves and nonlinear Scatchard plots similar to those reported for insulin target tissues, such as the hepatocyte and the adipocyte. Compared with those from adults, the RBCs from children had significantly greater numbers of insulin receptors per cell ( P < 0.05). The total insulin bound by the RBCs from both children and adults, however, was not different over the physiologic range of insulin concentrations. Cord blood RBCs showed greater numbers of receptors per cell than did those from either children or adults; however, the affinity for insulin was similar in both groups. The total amount of insulin bound by cord blood was significantly greater than that in either children ( P < 0.01) or adults ( P < 0.05) over the physiologic range of insulin concentrations. The method used to measure insulin binding by erythrocytes had relatively little intra- and interassay variability, and there was little diurnal variation in binding. Storage of heparinized blood at 4°C for 24-36h had no effect on insulin binding by the RBCs. We conclude that the measurement of insulin binding by RBCs from small volumes of blood may be particularly useful in the study of infants and children with disorders of carbohydrate metabolism to elucidate the role, if any, of abnormal receptor function in their condition.