The influence of gamma-irradiation upon the chemical and biological properties of insulin.

Partially purified insulin preparations of bovine and porcine origin, were subjected to gamma-irradiation with doses ranging from 1.0 up to 25 kGy (0.1-2.5 Mrad) at 0 degrees C or ambient temperature. The susceptibility of insulin to the irradiation was determined by chromatography, electrophoresis and assay of the biological activity. The sterilizing effect of the gamma-irradiation was investigated for Bacillus pumilus as well as for artificial mixtures of lactose and several bacilli. It is concluded that the sterilizing dose for the investigated insulins was greater than or equal to 2.2 kGy. At doses up to 25 kGy at 0 degree C no specific radiolytic products were detectable, whereas the biological activity was fully retained. The content of dimers and the content of related peptides appeared to increase gradually with the irradiation dose absorbed. No effects of long-term storage could be demonstrated on biological and chemical properties of insulin after 2.2, 4.5 and 7.5 kGy.