According to the literature, superoxide dismutase exists in all oxygen-metabolizing cells to protect cells from excessive superoxide. Under the action of SOD, two superoxide anions were converted to oxygen and hydrogen peroxide. The reaction principle is as follows: 

In mammals, there are three different forms of SOD: CuZn-SOD, Mn-SOD and EC-SOD (an extracellular form of SOD). Cu-Zn SOD exists in the cytoplasmic and mitochondrial membrane spaces of the cells, while Mn-SOD is located in the mitochondrial matrix.

1.  Determine optimal sampling volume of each sample before formal experiment. Calculate the inhibition ratio of serial sampling volume, and choose the optimal sampling volume when  inhibition ratio in the range of 25%~45%.

2.  The optimal sampling volume are different for different species, the SOD also are different for different samples. So it is best to do a pre-test to determining optimal sampling volume for a new sample.

3.  Adjust sampling volume: If inhibition ratio >55%, need to dilute the sample or decrease the sampling volume than take the test. If inhibition ratio < 15%, need to increase the sampling volume. 

      Sample pretreatment

(1)    Take 0.1 mL sample and add 0.1 mL Reagent 9. Mix thoroughly with a vortex mixer for 1 min by vortex mixer and centrifuge at 3500 g for 15 min. Take supernatant for CuZn-SOD measurement.

(2)    Take 0.1 mL normal saline and add 0.1 mL Reagent 9. Mix thoroughly for 1 min with a vortex mixer and centrifuge at 3500 g for 15 min. Take supernatant as control of CuZn-SOD.