Effect of alloxan diabetes and subsequent insulin treatment on temperature kinetics properties of succinate oxidase activity in rat kidney mitochondria

Early and late effects of alloxan diabetes and subsequent treatment with insulin on the temperature kinetics properties of succinate oxidase (SO) activity in rat kidney mitochondria were examined. In diabetic animals SO activity increased significantly and the increase was more pronounced at the late stage. Insulin treatment partially restored SO activity. However, the effect was temperature-dependent. In diabetic animals the energy of activation in the low temperature range (E_L) increased significantly while that in the high temperature range (E_H) decreased. The latter seems to be responsible for improving catalytic efficiency in the diabetic state. Insulin treatment normalized E_H only in the 1-month diabetic group. The phase transition temperature (Tt), decreased in diabetic animals. Insulin treatment caused an increase beyond the control value in Tt in 1-month diabetic animals. The results suggest that insulin status-dependent modulation of SO activity is a complex process.