On the Use of OH · Scavengers in Biological Systems

Abstract

The problem of using OH scavengers, with special emphasis on biological systems, is discussed. The problems arising from inhomogeneity and from possible large gradients in scavenger concentrations between the cell and media, or between different parts of the cell, are analysed, and their implications on scavenging efficiency are examined. The possible reactions of secondary radicals and their effect on scavenging and even on possible sensitization are described. The limitations of the usage of OH scavengers in biological systems are discussed.

On the spin trapping and ESR detection of oxygen-derived radicals generated inside cells.

“…Conversely, exposure of the erythrocytes to 10 mM azide for 10 min had no effect on the decay rate of DMPO-OH. Preheating the erythrocytes at 60'C for 5 Biochemistry: Samuni et al DISCUSSION Radical Production in the Cell. In the present study, high yields of OH radicals were radiolytically formed throughout the cell.…”

“…The average concentration of the principal cellular constitutents, including nucleic acids, nucleotides, proteins, and amino acids, were evaluated in the past assuming their homogeneous distribution throughout the cell (4). The respective rates of reaction (ktimes concentration) of the primary water-derived radicals OH, H, and e-with these cellular constituents have been considered and compared with the respective rates of reaction with various radical scavengers (5). This comparison indicated that scavengers such as tert-butyl alcohol, EtOH, 2-PrOH, and mannitol, within the concentration range commonly used for radioprotection, would trap a significant fraction of the radicals (5), provided that the endocellular concentration of the scavenger was comparable to that of the exocellular medium.…”

“…Initially, the spin trapping of radicals within cells might appear inapplicable in view of the high concentrations of the DNA, RNA, proteins, amino acids, etc. Analysis of competition kinetics indicated that despite the high concentrations of certain cellular constituents and large rate constants of their reactions with free radicals (4), various scavengers, including spin traps, can scavenge at least part of the radicals within whole cells (5). Even though formation under normal physiological conditions of oxygen-derived radicals by cells is well established, their detection by spin trapping might be difficult for several possible reasons.…”

Neutrophil degranulation inhibits potential hydroxyl-radical formation. Relative impact of myeloperoxidase and lactoferrin release on hydroxyl-radical production by iron-supplemented neutrophils assessed by spin-trapping techniques

“…The authors of these reports generally chose to interpret their results as evidence that neutrophils formed OH by an MPOdependent mechanism other than the Haber-Weiss reaction. More recent data [16][17][18][19][20][21][22][23][24] indicate that these assays are relatively non-specific and may yield similar oxidation products as a consequence of the presence of an MPO-derived oxidizing agent other than GOH.…”

“…These studies implied that neutrophils possessed the endogenous capacity for GOH formation. However, the specificity of the experimental techniques and 'scavenger agents' used to assess neutrophil GOH detection in these studies has been questioned [16][17][18][19][20][21][22][23][24]. In addition, the possibility was not excluded that exogenous iron contaminating the buffer systems allowed GOH to be produced.…”