title: Measuring the antioxidant capacity of blood plasma using potentiometry.
abstract: 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 (ΔE). ΔE presented a good inverse correlation with added increasing concentrations of ascorbate (2.5-75 μmol/L; R=-0.99), urate (9.0-150 μmol/L; R=-0.99), and bilirubin (0.78-13 μmol/L; R=-0.99). Increase in the antioxidant capacity decreased ΔE. Depletion of the antioxidant capacity by tert-butylhydroperoxide (6.5-50 μmol/L) presented a direct correlation (0.97) with ΔE. Furthermore, ΔE presented an inverse correlation (R=-0.99) with increased antioxidant capacity of plasma (FRAP) induced by the addition of ascorbate (2.5-75 μmol/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=6.5×10⁻³). These results demonstrate the adequacy of potentiometry for evaluating the antioxidant capacity of blood plasma samples.
authors.affiliation: Laboratory of Biochemistry of Exercise, Biochemistry Department, IB-UNICAMP, Campinas, SP, Brazil.
authors.forename: L S
authors.initials: LS
authors.lastname: Tessutti
authors.forename: D V
authors.initials: DV
authors.lastname: Macedo
authors.forename: L T
authors.initials: LT
authors.lastname: Kubota
authors.forename: A A
authors.initials: AA
authors.lastname: Alves
mesh_terms: D000293:Adolescent; D000818:Animals; D000975:Antioxidants / Q000032:analysis / Q000378:metabolism*; D001205:Ascorbic Acid / Q000097:blood / Q000378:metabolism; D015444:Exercise; D006801:Humans; D008297:Male; D018384:Oxidative Stress; D010949:Plasma / Q000378:metabolism*; D011199:Potentiometry / Q000379:methods*; D051381:Rats; D017208:Rats, Wistar; D017392:Thiobarbituric Acid Reactive Substances / Q000032:analysis / Q000378:metabolism; D014527:Uric Acid / Q000097:blood / Q000378:metabolism; D055815:Young Adult
chemical_list: D000975:Antioxidants; D017392:Thiobarbituric Acid Reactive Substances; D014527:Uric Acid; D001205:Ascorbic Acid
keywords: Exhaustive exercise; Plasma; Potentiometry; Total antioxidant capacity