Biological activity of some insulin derivatives

The ability of insulin and some of its derivatives to compete with 125 I-insulin for the binding site in the membrane fraction prepared from the mammary gland of lactating mice is reported. The binding affinity decreased in the following order: insulin desoctapeptide-insulin tert-butyloxycarbonyl 3 -insulin tert-butyloxycarbonyl 2 -desoctapeptide-insulin. Insulin hexamethyl ester and its desoctapeptide in concentrations 5.5 . 10 -11 - 2 . 10 -5 M did not inhibit the binding of 125 I-insulin. The comparison of the ability to decrease the blood glucose level showed that tert-butyloxycarbonyl 3 -insulin had 5% of the activity of insulin and that the other derivatives had less than 0.5% of that of insulin.