THE EFFECT OF ANTICOAGULANT CHOICE ON APPARENT TOTAL ANTIOXIDANT CAPACITY USING 3 DIFFERENT METHODS

We assessed total antioxidant capacity using three different methods, in plasma samples treated with either EDTA or heparin as anticoagulant , from 26 healthy subjects. Total antioxidant capacity was determined using an oxygen electrode (as the total peroxyl radical-trapping antio xidant parameter), by enhanced chemiluminescence, and by measurement o f the antioxidant-mediated quenching of the absorbance of a radical ca tion. The choice of anticoagulant had a profound effect on antioxidant capacity with heparinized plasma giving consistently higher values th an plasma anticoagulated with EDTA. Using the oxygen electrode the mea n value was 786.5 +/- 171.5 mu mol/L (heparin) compared to 681.4 +/- 1 60.4 mu mol/L (EDTA, P < 0.01). The chemiluminescence technique gave a mean antioxidant capacity of 915.6 +/- 214.1 mu mol/L in heparin samp les and 714.4 +/- 195.4 mu mol/L in EDTA samples (P < 0.0001). The abs orbance quenching technique gave a mean value of 867.0 +/- 199.2 mu mo l/L (heparin) and 675.5 +/- 245.4 mu mol/L (EDTA, P < 0.001). All meth ods tested showed comparable results for EDTA plasma, but the chemilum inescence technique gave higher apparent antioxidant capacity than eit her of the other two techniques when heparin plasma was used. We sugge st that either heparin is interacting to enhance antioxidant protectio n perhaps through release of superoxide dismutase, or the chelation of metal ions by EDTA is limiting the activity of antioxidant metalloenz ymes. Consistency in the choice of anticoagulant is clearly extremely important.