Ascorbyl radical formation in patients with sepsis: effect of ascorbate loading

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• 作者：Galley ; Helen F. ; Davies ; Michael J. ; Webster ; Nigel R.
• 关键词：Ascorbic acid ; Free radicals ; Iron ; Electron paramagnetic resonance spectroscopy ; Septicemia ; Spin traps ; Vitamin C
• 刊名：Free Radical Biology and Medicine
• 出版年：1996
• 出版时间：1996
• 年：1996
• 卷：20
• 期：1
• 页码：139-143
• 全文大小：438 K

文摘

Patients with sepsis have low concentrations of antioxidants, including ascorbic acid, and also have increased concentrations of markers of free radical damage. Although ascorbic acid is a potent antioxidant, it can act as a prooxidant by promoting iron-catalysed reactions. We measured baseline total vitamin C and bleomycin-detectable “free” iron levels and ascorbyl radical concentrations before and after intravenous infusion of 1 g ascorbic acid in patients with sepsis and healthy control subjects. Vitamin C concentrations were decreased in patients compared to healthy subjects (p < 0.0001), and “free” iron was increased (p < 0.002). Preinfusion ascorbyl radical concentrations were not different in patients and controls. Postinfusion ascorbyl radical levels increased in both controls and patients, with larger increases in healthy subjects (p < 0.0001), suggesting suboptimal basal vitamin C levels and increased scavenging of a constant oxidant pool by ascorbate in the controls. In the patients, who were all vitamin C deficient, infused ascorbate was rapidly consumed, either via the promotion of redox cycling of iron or as a result of radical scavenging. This study demonstrates markedly different handling of infused ascorbate in patients with sepsis and healthy subjects, and further studies are needed to elucidate the relative anti- and pro-antioxidant mechanisms of ascorbate in patients with raised “free” iron levels.