The use of potentiometry to measure plasma antioxidant capacity to contribute to oxidative stress evaluation
is presented. In this assay, plasma (n = 60) diluted (0.3 to 1 ml) in phosphate buffer, pH 7.4, NaCl
9%, was submitted to potentiometry. A platinum wire was the working electrode and saturated calomel
the reference. The results are presented as the difference between sample and buffer potential (DE). DE
presented a good inverse correlation with added increasing concentrations of ascorbate (2.575 lmol/L;
R = 0.99), urate (9.0150 lmol/L; R = 0.99), and bilirubin (0.7813 lmol/L; R = 0.99). Increase in the
antioxidant capacity decreased DE. Depletion of the antioxidant capacity by tert-butylhydroperoxide
(6.550 lmol/L) presented a direct correlation (0.97) with DE. Furthermore, DE presented an inverse correlation
(R = 0.99) with increased antioxidant capacity of plasma (FRAP) induced by the addition of
ascorbate (2.575 lmol/L). The response of the potentiometric method proved be adequate for measuring
the plasma antioxidant depletion induced by acute exhaustive exercise in rats (control, n = 15; exercised,
n = 15). This exercise decreased the concentration of urate (p < 0.05), decreased FRAP (p < 0.5),
increased TBARS (p < 0.5), and decreased the potentiometer sensor response (p = 6.5 103
). These
results demonstrate the adequacy of potentiometry for evaluating the antioxidant capacity of blood
plasma samples.
2013 Els