Abstract
A simple radioreceptor assay for insulin using rat liver membranes as receptor sites, with sufficient specificity, precision, and sensitivity to detect 10ng or 276μU/ml of serum insulin, has been developed. In the presence of standard porcine insulin at the concentration of 1.0ng/tube, approximately 8% of 125I-porcine insulin was bound to the plasma membranes and ninety-five per cent of this binding was inhibited by 1.0μg of standard insulin per tube. Four animal insulins inhibited the binding of 125I-insulin while ACTH, glucagon, human growth hormone, and oxytocin were inert. Insulin values in dog pancreatic vein sera obtained during and after glucose loading and measured by the present radioreceptor assay agreed well with immunoreactive insulin. The ratio of IRI to the measurement by radioreceptor assay was 1.09±0.18 for the same sera.
