Saran M, Bors W
GSF-Forschungszentrum für Umwelt und Gesundheit, Institut für Strahlenbiologie, Neuherberg, Germany.
Radiat Res. 1997 Jan;147(1):70-7.
Contrary to common belief, hydrogen peroxide (H2O2) and hypochlorite (HOCl) are not produced continuously and independently during the irradiation of buffer solution containing chloride. Different buildup and decay reactions are involved in a complex interaction of these substances during irradiation. Which of the species predominates is determined by the parameters of the solution. The amount of either compound detectable after irradiation depends on the dissolved gas (O2, N2O or N2), on the pH value and to some extent on the presence of catalytic metals: Under slightly acidic conditions, low oxygen content and high generation rates of OH radicals, the only detectable species is hypochlorite; at high oxygen content and at pH values in the physiological range, hydrogen peroxide is the main detectable product. However, H2O2 and HOCl react with each other in a pH-dependent way, yielding the stable products O2 and Cl-. This reaction limits the expected lifetime of both species in aqueous solution to some tens of seconds. Therefore, analysis of the sample solution after irradiation determines only the substance that was present in greater relative concentration at the termination of irradiation. Such analysis, however, does not allow conclusions about the processes that occurred during irradiation. We have investigated the decay and formation reactions of H2O2 and HOCl under all relevant irradiation conditions and found evidence that the formation and further reaction of HOCl-, the precursor of HOCl, is of central importance even in cases where no significant amounts of H2O2 or HOCl are detectable after irradiation. We discuss the consequences of these results for the cytotoxicity observed after irradiation of cells suspended in physiological saline and conclude that analogous processes must also be relevant for irradiations under in vivo conditions.
与普遍看法相反，在含有氯化物的缓冲溶液辐照过程中，过氧化氢（H2O2）和次氯酸盐（HOCl）并非持续且独立产生。在辐照期间，这些物质的复杂相互作用涉及不同的生成和衰减反应。哪种物质占主导取决于溶液的参数。辐照后可检测到的任何一种化合物的量取决于溶解气体（O2、N2O或N2）、pH值，在一定程度上还取决于催化金属的存在：在弱酸性条件、低氧含量和高OH自由基生成速率下，唯一可检测到的物质是次氯酸盐；在高氧含量和生理范围内的pH值下，过氧化氢是主要的可检测产物。然而，H2O2和HOCl以pH依赖的方式相互反应，生成稳定产物O2和Cl-。该反应将两种物质在水溶液中的预期寿命限制在几十秒。因此，辐照后对样品溶液的分析仅能确定辐照结束时相对浓度较高的物质。然而，这种分析无法得出关于辐照期间发生的过程的结论。我们研究了在所有相关辐照条件下H2O2和HOCl的衰减和形成反应，发现有证据表明，即使在辐照后未检测到大量H2O2或HOCl的情况下，HOCl的前体HOCl-的形成和进一步反应也至关重要。我们讨论了这些结果对悬浮在生理盐水中的细胞辐照后观察到的细胞毒性的影响，并得出结论，类似的过程在体内条件下的辐照中也必定相关。
