[The determination of the biological activity of insulin by a radioreceptor method]

A new in vitro radioreceptor assay method for determining the biological activity of insulin substances is put forward. This method is designed mainly to serve the purposes of practice. It perfectly substitutes the biological, expensive labour-taking and slow pharmacopoeial method. It is reproducible, does not depend on the season and reduces the species differences to minimum by using a mixture of bovine and porcine insulins (Forth International Standard) as the source of unlabeled insulin. The rat liver membrane receptors (preparations) retained their insulin-binding ability up to 10 months, when stored at -18 degrees C-(-)20 degrees C. By means of this method the biological activity in different insulin preparations is established. It is found that this activity is highest in the monocomponent insulin substances, followed by the single-peak insulins and it's lowest in the conventional insulins.