Radioreceptor assay for insulin.

A sensitive and simple radioreceptor assay (RRA) capable of detecting 10 muU/ml of serum insulin has been developed using the crude membrane fraction of guinea pig kidney and 125I-porcine insulin. Using this assay system, serum insulin during 100 g oral glucose tolerance tests in six males including one obese man was measured. The mean concentration of serum insulin increased from 19 muU/ml during fasting to maximum of 90 muU/ml after 60 min of glucose load and then gradually declined to 38 muU/ml by 180 min. The values obtained by the present RRA agreed well with immunoreactive insulin (IRI).