Effect of different gamma radiation doses on solid crystalline insulin: hypoglycaemia in diabetic beagle dogs

The effect of different doses of gamma radiation (25, 50 and 100 KGy) on the solid crystalline insulin was studied. The results showed that there was no significant difference (P > 0.05) between the hypoglycaemic effects of 25 kGy gamma-irradiated and the non-irradiated insulin as indicated by the plasma glucose levels and the relative hypoglycaemia. The exposure of insulin to higher doses of radiations (50 and 100 kGy) resulted in almost the same hypoglycaemic effect, which was however greater than that produced by the 25 kGy gamma-irradiated and the non-irradiated insulin. The DSC thermograms showed that the thermal behaviour of crystalline insulin was not affected by the different doses of irradiation. However, a slight colour change was noticed on samples exposed to 50 and 100 kGy of radiation but not on samples subjected to 25 KGy. In conclusion, while the routinely used dose (25 kGy) of gamma radiation for sterilization does not seem to affect the activity of insulin, higher doses of radiation (50 and 100 kGy) enhance its hypoglycaemic effect.