How do erythrocytes contribute to the ABTS* scavenging capacity of blood?

Abstract

It has been suggested lately that erythrocytes contribute significantly to the oxidant scavenging capacity (OSC) of blood and that surface adsorption of polyphenols enhances the antioxidant capacity of erythrocytes. The aim of this study was to examine the contribution of erythrocytes to the OSC of whole blood measured with a substrate not penetrating into the cells. Comparison of reduction of 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) radical (ABTS*) by whole blood and blood plasma indicates that erythrocytes do contribute to ABTS* reduction but their contribution is lower with respect to plasma. ABTS* reduction by erythrocytes and its enhancement by polyphenols were inhibited by thiol reagents (N-ethylmaleimide and iodacetate). These reagents inhibited also the reduction of extracellular ferricyanide by erythrocytes and its enhancement by polyphenols. On this basis we postulate that the contribution of erythrocytes to the blood OSC estimated by ABTS* decolorization is at least partly due to the transmembrane-reducing system, which activity is routinely assayed by ferricyanide reduction.