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Updated: Oct 13, 2026

A Rapid and Specific Microplate Assay for the Determination of Intra- and Extracellular Ascorbate in Cultured Cells
Published on: April 11, 2014
Ascorbate and cysteine-mediated selective neutralisation of extracellular oxidants during N-formyl peptide activation
Abstract:
The effects of sodium ascorbate and cysteine (2.5 X 10(-5) M-2.5 X 10(-4) M) on the intensity and profile of luminol-enhanced chemiluminescence, superoxide generation, extracellular myeloperoxidase (MPO) activity and auto-iodination were measured in purified human polymorphonuclear leukocytes activated by the leukoattractant FMLP in vitro. Chemiluminescence studies were also performed using a whole-blood method. Cysteine (10(-4) M-2.5 X 10(-4) M) and ascorbate (2.5 X 10(-5) M-2.5 X 10(-4) M) caused significant inhibition of the early extracellular peak of FMLP-activated chemiluminescence and increased the intensity of the later occurring intracellular peak in both PMNL and blood. At the same concentrations both agents scavenged superoxide released by FMLP-activated PMNL, inhibited oxidant generation by extracellular MPO and decreased FMLP-induced auto-oxidation of PMNL. Administration of a single 1 gram oral dose of ascorbate to adult human volunteers was associated with significant reduction and enhancement respectively of the extracellular and intracellular luminol-enhanced chemiluminescence responses of FMLP-activated blood. These results show that the water soluble anti-oxidants cysteine and especially ascorbate selectively neutralise the reactivity of harmful reactive oxidants released by phagocytes, whilst the intracellular generation of antimicrobial oxidants remains intact.
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