Radioreceptor assay of insulin using rabbit erythrocyte membrane

A simple radioreceptor assay for insulin was established with sensitivity sufficient to detect 10 mu U/ml of insulin in human sera. This radioreceptor assay was carried out at 00 using rabbit erythrocyte membranes. The binding assay for the standard curve was performed in the presence of insulin-free serum, since the binding of insulin was greatly reduced by the addition of serum. Under the conditions used, 38% of the initial binding of 125I-insulin was displaced by 250 mu U/ml of native insulin. The sensitivity of the radioreceptor assay was dependent on the concentrations of both membrane protein and 125I-insulin. The ratio of immunoreactive insulin to insulin values obtained by the present assay was 0.93 +- 0.10 for 19 healthy and diabetic subjects. (author)