Abstract
Insulin-like activity (NSILA-s) in human blood which is not suppressed by insulin antibody was recently extracted and purified from human serum, and a radioreceptor assay (RRA) was developed to measure the insulin-like activity instead of bioassay. Based on the finding that somatomedine-c, like NSILA-s is a competitive inhibitor of 125I-insulin binding to its receptor prepared from human placenta cell menbranes, RRA using insulin receptors solubilized from human placenta cell membranes was developed to measure NSILA-s.
The biological activity of the partially purified NSILA-s obtained was 6.3 to 8. 6 mU/mg, and the average was 7.1 mU/mg, as assayed by the isolated rat epididymal adipose cell method. NSILA-s was finally purified to the extent of 3550 times compared to the starting material. The activity as assayed by RRA was 8.8 mU/mg, which was closely almost similar to that estimated by bioassay.
